draft-ietf-sipcore-rfc4244bis-01.txt   draft-ietf-sipcore-rfc4244bis-02.txt 
Network Working Group M. Barnes Network Working Group M. Barnes
Internet-Draft Polycom Internet-Draft Polycom
Obsoletes: 4244 (if approved) F. Audet Obsoletes: 4244 (if approved) F. Audet
Intended status: Standards Track Skype Intended status: Standards Track Skype
Expires: December 26, 2010 S. Schubert Expires: April 29, 2011 S. Schubert
NTT NTT
J. van Elburg J. van Elburg
Detecon International Gmbh Detecon International Gmbh
C. Holmberg C. Holmberg
Ericsson Ericsson
June 24, 2010 October 26, 2010
An Extension to the Session Initiation Protocol (SIP) for Request An Extension to the Session Initiation Protocol (SIP) for Request
History Information History Information
draft-ietf-sipcore-rfc4244bis-01.txt draft-ietf-sipcore-rfc4244bis-02.txt
Abstract Abstract
This document defines a standard mechanism for capturing the history This document defines a standard mechanism for capturing the history
information associated with a Session Initiation Protocol (SIP) information associated with a Session Initiation Protocol (SIP)
request. This capability enables many enhanced services by providing request. This capability enables many enhanced services by providing
the information as to how and why a call arrives at a specific the information as to how and why a call arrives at a specific
application or user. This document defines an optional SIP header, application or user. This document defines an optional SIP header,
History-Info, for capturing the history information in requests. A History-Info, for capturing the history information in requests. SIP
SIP/SIPS URI parameter is defined to tag information necessary to header field parameters are defined to tag the method by which the
populate the History-Info header. In addition, this document defines target of a request is determined. In addition, this document
a value for the Privacy header specific to the History-Info header. defines a value for the Privacy header specific to the History-Info
header.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 26, 2010. This Internet-Draft will expire on April 29, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
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the copyright in such materials, this document may not be modified the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format not be created outside the IETF Standards Process, except to format
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than English. than English.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 4 2. Conventions and Terminology . . . . . . . . . . . . . . . . . 4
3. Overview of Operations . . . . . . . . . . . . . . . . . . . . 5 3. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. General User Agent Behavior . . . . . . . . . . . . . . . . . 9 4. Overview of Operation . . . . . . . . . . . . . . . . . . . . 6
4.1. User Agent Client (UAC) Behavior . . . . . . . . . . . . . 9 5. General User Agent Behavior . . . . . . . . . . . . . . . . . 10
4.2. User Agent Server (UAS) Behavior . . . . . . . . . . . . . 10 5.1. User Agent Client (UAC) Behavior . . . . . . . . . . . . . 10
4.2.1. Processing of Requests with History-Info . . . . . . . 10 5.2. User Agent Server (UAS) Behavior . . . . . . . . . . . . . 10
4.2.2. Generation of Responses with History-Info . . . . . . 10 5.2.1. Processing of Requests with History-Info . . . . . . . 10
4.3. Redirect Server Behavior . . . . . . . . . . . . . . . . . 11 5.2.2. Generation of Responses with History-Info . . . . . . 11
5. Proxy Behavior . . . . . . . . . . . . . . . . . . . . . . . . 11 5.3. Redirect Server Behavior . . . . . . . . . . . . . . . . . 11
5.1. Adding the History-Info Header to Requests . . . . . . . . 11 6. Proxy Behavior . . . . . . . . . . . . . . . . . . . . . . . . 12
5.1.1. Initial Request . . . . . . . . . . . . . . . . . . . 11 6.1. Adding the History-Info Header to Requests . . . . . . . . 12
5.1.2. Re-sending based on failure response . . . . . . . . . 12 6.1.1. Initial Request . . . . . . . . . . . . . . . . . . . 12
5.1.3. Re-sending based on redirection response . . . . . . . 13 6.1.2. Re-sending based on failure response . . . . . . . . . 13
5.2. Sending History-Info in Responses . . . . . . . . . . . . 14 6.1.3. Re-sending based on redirection response . . . . . . . 14
6. The History-Info header field . . . . . . . . . . . . . . . . 14 6.2. Sending History-Info in Responses . . . . . . . . . . . . 14
6.1. Definition . . . . . . . . . . . . . . . . . . . . . . . . 14 7. The History-Info header field . . . . . . . . . . . . . . . . 14
6.2. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 16 7.1. Definition . . . . . . . . . . . . . . . . . . . . . . . . 14
6.3. Procedures . . . . . . . . . . . . . . . . . . . . . . . . 16 7.2. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.3.1. SIP/SIPS URI target parameter for History-Info 7.3. Procedures . . . . . . . . . . . . . . . . . . . . . . . . 17
Header . . . . . . . . . . . . . . . . . . . . . . . . 17 7.3.1. Privacy in the History-Info Header . . . . . . . . . . 17
6.3.2. Privacy in the History-Info Header . . . . . . . . . . 17 7.3.2. Reason in the History-Info Header . . . . . . . . . . 18
6.3.3. Reason in the History-Info Header . . . . . . . . . . 18 7.3.3. Indexing in the History-Info Header . . . . . . . . . 18
6.3.4. Indexing in the History-Info Header . . . . . . . . . 19 7.3.4. Request Target in the History-Info Header . . . . . . 20
6.3.5. Request Target in the History-Info Header . . . . . . 20 8. Application Considerations . . . . . . . . . . . . . . . . . . 21
7. Application Considerations . . . . . . . . . . . . . . . . . . 20 9. Security Considerations . . . . . . . . . . . . . . . . . . . 22
8. Security Considerations . . . . . . . . . . . . . . . . . . . 22 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 10.1. Registration of New SIP History-Info Header . . . . . . . 23
9.1. Registration of New SIP History-Info Header . . . . . . . 22 10.2. Registration of "history" for SIP Privacy Header . . . . . 24
9.2. Registration of "history" for SIP Privacy Header . . . . . 23 10.3. Registration of Header Field Parameters . . . . . . . . . 24
9.3. Registration of "hit" SIP/SIPS URI Parameter . . . . . . . 23 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 25
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 24 12. Changes from RFC 4244 . . . . . . . . . . . . . . . . . . . . 25
11. Changes from RFC 4244 . . . . . . . . . . . . . . . . . . . . 24 12.1. Backwards compatibility . . . . . . . . . . . . . . . . . 26
11.1. Backwards compatibility . . . . . . . . . . . . . . . . . 26 13. Changes since last Version . . . . . . . . . . . . . . . . . . 27
12. Changes since last Version . . . . . . . . . . . . . . . . . . 26 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 32
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29 14.1. Normative References . . . . . . . . . . . . . . . . . . . 32
13.1. Normative References . . . . . . . . . . . . . . . . . . . 29 14.2. Informative References . . . . . . . . . . . . . . . . . . 32
13.2. Informative References . . . . . . . . . . . . . . . . . . 30 Appendix A. Request History Requirements . . . . . . . . . . . . 33
Appendix A. Request History Requirements . . . . . . . . . . . . 30 A.1. Security Requirements . . . . . . . . . . . . . . . . . . 34
A.1. Security Requirements . . . . . . . . . . . . . . . . . . 32 A.2. Privacy Requirements . . . . . . . . . . . . . . . . . . . 35
A.2. Privacy Requirements . . . . . . . . . . . . . . . . . . . 32 Appendix B. Example call flows . . . . . . . . . . . . . . . . . 35
Appendix B. Example call flows . . . . . . . . . . . . . . . . . 33 B.1. Sequentially Forking (History-Info in Response) . . . . . 35
B.1. Sequentially Forking (History-Info in Response) . . . . . 33 B.2. History-Info with Privacy Header . . . . . . . . . . . . . 43
B.2. History-Info with Privacy Header . . . . . . . . . . . . . 40 B.3. Privacy Header for a Specific History-Info Entry . . . . . 45
B.3. Privacy Header for a Specific History-Info Entry . . . . . 41 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 46
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 43
1. Introduction 1. Introduction
Many services that SIP is anticipated to support require the ability Many services that SIP is anticipated to support require the ability
to determine why and how the call arrived at a specific application. to determine why and how the call arrived at a specific application.
Examples of such services include (but are not limited to) sessions Examples of such services include (but are not limited to) sessions
initiated to call centers via "click to talk" SIP Uniform Resource initiated to call centers via "click to talk" SIP Uniform Resource
Locators (URLs) on a web page, "call history/logging" style services Locators (URLs) on a web page, "call history/logging" style services
within intelligent "call management" software for SIP User Agents within intelligent "call management" software for SIP User Agents
(UAs), and calls to voicemail servers. Although SIP implicitly (UAs), and calls to voicemail servers. Although SIP implicitly
provides the redirect/retarget capabilities that enable calls to be provides the retarget capabilities that enable calls to be routed to
routed to chosen applications, there is a need for a standard chosen applications, there is a need for a standard mechanism within
mechanism within SIP for communicating the retargeting history of SIP for communicating the retargeting history of such a request.
such a request. This "request history" information allows the This "request history" information allows the receiving application
receiving application to determine hints about how and why the call to determine hints about how and why the call arrived at the
arrived at the application/user. application/user.
This document defines a SIP header, History-Info, to provide a This document defines a SIP header, History-Info, to provide a
standard mechanism for capturing the request history information to standard mechanism for capturing the request history information to
enable a wide variety of services for networks and end-users. A SIP/ enable a wide variety of services for networks and end-users. SIP
SIPS URI parameter is defined to tag information necessary to header field parameters are defined to tag the method by which the
populate the History-Info header. In addition, this document defines target of a request is determined. In addition, this document
a value for the Privacy header specific to the History-Info header. defines a value for the Privacy header specific to the History-Info
header.
The History-Info header provides a building block for development of The History-Info header provides a building block for development of
SIP based applications and services. The requirements for the SIP based applications and services. The requirements for the
solution described in this document are included in Appendix A. solution described in this document are included in Appendix A.
Example scenarios using the History-Info header are included in Example scenarios using the History-Info header are included in
Appendix B. Appendix B.
2. Conventions and Terminology 2. Conventions and Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
The term "retarget" is used in this document to refer both to the The term "retarget" is used in this document to refer to the process
process of a Proxy Server/User Agent Client (UAC) changing a Uniform of a SIP entity changing a Uniform Resource Identifier (URI) in a
Resource Identifier (URI) in a request based on the rules for request based on the rules for determining request targets as
determining request targets as described in Section 16.5 of [RFC3261] described in Section 16.5 of [RFC3261] and of the subsequent
and the subsequent forwarding of that request as described in section forwarding of that request as described in step 2 in section 16.6 of
16.6 of [RFC3261]. [RFC3261]. This includes changing the Request-URI due to a location
service lookup and redirect processing. This also includes internal
The term "forward" is used consistent with the terminology in (to a proxy/SIP intermediary) changes of the URI prior to forwarding
[RFC3261]. Noting that [RFC3261] uses the term "forwarding" to of the request.
describe a proxy's handling of requests for domains for which is not
responsible, as well as to describe the basic "forwarding" of a
request (in section 16.6) once a target has been determined.
However, the context of the usage is sufficient to differentiate the The terms "location service", "forward", "redirect" and "AOR" are
slightly different meanings. used consistent with the terminology in [RFC3261].
The terms "location service", "redirect" and "AOR" are used The references to "domain for which the SIP entity/Proxy/Intermediary
consistent with the terminology in [RFC3261]. is responsible" are consistent with and intended to convey the same
context as the usage of that terminology in [RFC3261]. The
applicability of History-Info to architectures or models outside the
context of [RFC3261] is outside the scope of this specification.
3. Overview of Operations 3. Background
SIP implicitly provides retargeting capabilities that enable calls to SIP implicitly provides retargeting capabilities that enable calls to
be routed to specific applications as defined in [RFC3261]. The be routed to specific applications as defined in [RFC3261]. The
motivation for capturing the request history is that in the process motivation for capturing the request history is that in the process
of retargeting a request, old routing information can be forever of retargeting a request, old routing information can be forever
lost. This lost information may be important history that allows lost. This lost information may be important history that allows
elements to which the call is retargeted to process the call in a elements to which the call is retargeted to process the call in a
locally defined, application-specific manner. This document defines locally defined, application-specific manner. This document defines
a mechanism for transporting the request history. Application- a mechanism for transporting the request history. Application-
specific behavior is outside the scope of this specification. specific behavior is outside the scope of this specification.
skipping to change at page 6, line 12 skipping to change at page 6, line 13
[RFC5627], which can be overwritten by a home proxy upon receipt [RFC5627], which can be overwritten by a home proxy upon receipt
of the initial request. of the initial request.
o Facilitating the use of limited use addresses (minted on demand) o Facilitating the use of limited use addresses (minted on demand)
and sub-addressing. and sub-addressing.
o Preserving service specific URIs that can be overwritten by a o Preserving service specific URIs that can be overwritten by a
downstream proxy, such as those defined in [RFC3087], and control downstream proxy, such as those defined in [RFC3087], and control
of network announcements and IVR with SIP URI [RFC4240]. of network announcements and IVR with SIP URI [RFC4240].
o A stronger security solution for SIP. A side effect is that each 4. Overview of Operation
proxy that captures the "request history" information in a secure
manner provides an additional means (without requiring signed
keys) for the original requestor to be assured that the request
was properly retargeted.
The fundamental functionality provided by the request history The fundamental functionality provided by the request history
information is the ability to inform proxies and UAs involved in information is the ability to inform proxies and UAs involved in
processing a request about the history or progress of that request processing a request about the history or progress of that request
(CAPABILITY-req, see Appendix A). The solution is to capture the (CAPABILITY-req, see Appendix A). The solution is to capture the
Request-URIs as a request is retargeted, in a SIP header: History- Request-URIs as a request is retargeted, in a SIP header: History-
Info (CONTENT-req, see Appendix A). This allows for the capturing of Info (CONTENT-req, see Appendix A). This allows for the capturing of
the history of a request that would be lost with the normal SIP the history of a request that would be lost with the normal SIP
processing involved in the subsequent retargeting of the request. processing involved in the subsequent retargeting of the request.
The History-Info header can appear in any request not associated with The History-Info header can appear in any request not associated with
an established dialog (e.g., INVITE, REGISTER, MESSAGE, REFER and an early or established dialog (e.g., INVITE, REGISTER, MESSAGE,
OPTIONS, PUBLISH and SUBSCRIBE, etc.) (REQUEST-VALIDITY-req, see REFER and OPTIONS, PUBLISH and SUBSCRIBE, etc.) (REQUEST-VALIDITY-
Appendix A) and any valid response to these requests (ISSUER-req, see req, see Appendix A) and any provisional or final responses to these
Appendix A). requests (ISSUER-req, see Appendix A).
This specification defines parameters detailed in Section 6.1 for The following information is carried in the History-Info header as
carrying the following information in the History-Info header: detailed in Section 7.1:
o Targeted-to-URI: The targeted-to-URI entry captures the Request- o Targeted-to-URI: The targeted-to-URI entry captures the Request-
URI for the specific request as it is forwarded. URI for the specific request as it is forwarded.
o Index: The index reflects the chronological order of the o Index: The index reflects the chronological order of the
information, indexed to also reflect the forking and nesting of information, indexed to also reflect the forking and nesting of
requests. requests.
o Reason: Reason describes why an entry was retargeted. o Reason: Reason describes why an entry was retargeted.
o Privacy: Privacy is used to request that an entry be anonymized in o Privacy: Privacy is used to request that an entry be anonymized if
the case of a request that is retargeted to a domain for which the the request is retargeted to a domain for which the retargeting
retargeting entity is not responsible. entity is not responsible.
o Target: The target parameter indicates whether the Targeted-to-URI
is a registered contact ("rc") for or another user mapped ("mp")
from the Request-URI in the incoming request that was retargeted.
This specification also defines the "hit" SIP/SIPS URI Parameter. o Target: A parameter indicating whether the Targeted-to-URI is a
This parameter is added to URIs as they are added to the target list registered contact ("rc") for another user mapped ("mp") from the
for a request based on the same criteria as the target parameter Request-URI in the incoming request that was retargeted. The
described above. This URI parameter is used to determine the value index of the History-Info entry for the URI that was retargeted is
for the target parameter. Further detail is provided in included in each of these parameters. Note that there may be
Section 6.3.1. other reasons a request is retargeted such as normal routing and
forwarding, strict routing, etc., thus not all history-info
entries have a target header field parameter. The "rc" and "mp"
scenarios are what is anticipated to be most useful to end
applications/users.
In addition, this specification defines a value for the Privacy In addition, this specification defines a value for the Privacy
header, "history", that applies to all the History-Info header header, "history", that applies to all the History-Info header
entries in a Request or to a specific History-Info header entry as entries in a Request or to a specific History-Info header entry as
described above. Further detailed is provided in Section 6.3.2. described above. Further detailed is provided in Section 7.3.1.
The History-Info header is added to a Request when a new request is
created by a UAC or forwarded by a Proxy, or when the target of a
request is changed. It is possible for the target of a request to be
changed by the same proxy/SIP Intermediary multiple times (referred
to as 'internal retargeting'). A SIP entity changing the target of a
request in response to a redirect or REFER also propagates any
History-Info header from the initial Request in the new request.
The following is an illustrative example of usage of History-Info. The following is an illustrative example of usage of History-Info.
In this example, Alice (sip:alice@atlanta.example.com) calls Bob In this example, Alice (sip:alice@atlanta.example.com) calls Bob
(sip:bob@biloxi.example.com). Alice's home proxy (sip: (sip:bob@biloxi.example.com). Alice's home proxy (sip:
atlanta.example.com) forwards the request to Bob's proxy (sip: atlanta.example.com) forwards the request to Bob's proxy (sip:
biloxi.example.com). When the request arrives at sip: biloxi.example.com). When the request arrives at sip:
biloxi.example.com, it does a location service lookup for biloxi.example.com, it does a location service lookup for
bob@biloxi.example.com and changes the target of the request to Bob's bob@biloxi.example.com and changes the target of the request to Bob's
Contact URIs provided as part of normal SIP registration. In this Contact URIs provided as part of normal SIP registration. In this
example, Bob is simultaneously contacted on a PC client and on a example, Bob is simultaneously contacted on a PC client and on a
phone, and Bob answers on the PC client. phone, and Bob answers on the PC client.
One important thing illustrated by this call flow is that without One important thing illustrated by this call flow is that without
History-Info, Bob would "lose" the target information, including any History-Info, Bob would "lose" the target information, including any
parameters in the request URI. Bob can now recover that information parameters in the request URI. Bob can recover that information by
by locating the first entry just prior to the last hi-entry marked as locating the last hi-entry with an "rc" header field parameter. This
"rc", which is one level up in indexing from the last hi-entry - "rc" parameter contains the index of the hi-entry containing the lost
i.e., the sip:bob@biloxi.example.com entry with index=1.1. target information - i.e., the sip:bob@biloxi.example.com entry with
index=1.1. Note that an hi-entry is not included for the fork to
sip:bob@192.0.2.7 since there was no response at the time the 200 OK
is sent to Alice.
The formatting in this scenario is for visual purposes; thus, The formatting in this scenario is for visual purposes; thus,
backslash and CRLF are used between the fields for readability and backslash and CRLF are used between the fields for readability and
the headers in the URI are not shown properly formatted for escaping. the headers in the URI are not shown properly formatted for escaping.
Refer to Section 6.2 for the proper formatting. Additional detailed Refer to Section 7.2 for the proper formatting. Additional detailed
scenarios are available in the Appendix B. scenarios are available in the Appendix B.
Note: This example uses loose routing procedures. Note: This example uses loose routing procedures.
Alice atlanta.example.com biloxi.example.com Bob@pc Bob@phone Alice atlanta.example.com biloxi.example.com Bob@pc Bob@phone
| | | | | | | | | |
| INVITE sip:bob@biloxi.example.com;p=x | | | INVITE sip:bob@biloxi.example.com;p=x | |
|--------------->| | | | |--------------->| | | |
| Supported: histinfo | | | | Supported: histinfo | | |
| | | | | | | | | |
| | INVITE sip:bob@biloxi.example.com;p=x | | INVITE sip:bob@biloxi.example.com;p=x |
| |--------------->| | | | |--------------->| | |
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1 |
| | | | | | | | | |
| | | INVITE sip:bob@192.0.2.3 | | | INVITE sip:bob@192.0.2.3|
| | |--------------->| | | | |--------------->| |
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| History-Info: <sip:bob@192.0.2.3>;index=1.1.1;rc | History-Info: <sip:bob@192.0.2.3>;index=1.1.1;rc=1.1
| | | | | | | | | |
| | | INVITE sip:bob@192.0.2.7 | | | INVITE sip:bob@192.0.2.7|
| | |-------------------------->| | | |-------------------------->|
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| History-Info: <sip:bob@192.0.2.7>;index=1.1.2;rc | History-Info: <sip:bob@192.0.2.7>;index=1.1.2;rc=1.1
| | | 200 | | | | | 200 | |
| | |<---------------| | | | |<---------------| |
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| History-Info: <sip:bob@192.0.2.3>;index=1.1.1;rc | History-Info: <sip:bob@192.0.2.3>;index=1.1.1;rc=1.1
| | | | | | | | | |
| | |<===Proxy cancels INVITE==>|
| | 200 | | | | | 200 | | |
| |<---------------| | | | |<---------------| | |
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| History-Info: <sip:bob@192.0.2.3>;index=1.1.1;rc | History-Info: <sip:bob@192.0.2.3>;index=1.1.1;rc=1.1
| History-Info: <sip:bob@192.0.2.7?Reason=SIP;cause=487>;\ | | | | |
| index=1.1.2;rc | | | Proxy Cancels INVITE |
| | |<=========================>|
| | | | | | | | | |
| 200 | | | | | 200 | | | |
|<---------------| | | | |<---------------| | | |
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| History-Info: <sip:bob@192.0.2.3;index=1.1.1;rc | History-Info: <sip:bob@192.0.2.3;index=1.1.1;rc=1.1
| History-Info: <sip:bob@192.0.2.7?Reason=SIP;cause=487>;\
| index=1.1.2;rc
| | | | | | | | | |
| ACK | | | | | ACK | | | |
|--------------->| ACK | | | |--------------->| ACK | | |
| |--------------->| ACK | | | |--------------->| ACK | |
| | |--------------->| | | | |--------------->| |
Figure 1: Basic Call Figure 1: Basic Call
4. General User Agent Behavior 5. General User Agent Behavior
This section describes the processing specific to UAs for the This section describes the processing specific to UAs for the
History-Info header. History-Info header.
4.1. User Agent Client (UAC) Behavior 5.1. User Agent Client (UAC) Behavior
The UAC SHOULD include the "histinfo" option tag in the Supported The UAC MUST include the "histinfo" option tag in the Supported
header in any request not associated with an established dialog for header in any new or out-of-dialog request for which the UAC would
which the UAC would like the History-Info header in the response. In like the History-Info header in the response. In addition, the UAC
addition, the UAC MAY add a History-Info header, using the Request- SHOULD add a History-Info header, using the Request-URI of the
URI of the request as the hi-target-to-uri, in which case the index request as the hi-targeted-to-uri, in which case the index MUST be
MUST be set to a value of 1 in the hi-entry. As a result, set to a value of 1 in the hi-entry. As a result, intermediaries and
intermediaries and the UAS at least know the original Request-URI, the UAS at least know the original Request-URI, and if the Request-
and if the Request-URI was modified by a previous hop. Normally, URI was modified by a previous hop. In the case of a B2BUA
UACs are not expected to include a History-Info header in an initial implementation, a UAC MAY add the hi-entries received in the incoming
request as it is more of a Proxy function; the main reason it is request at the UAS to the subsequent outgoing request.
allowed is for B2BUAs who are performing proxy-like functions such as
routing.
A UAC that does not want an hi-entry added due to privacy A UAC that does not want an hi-entry added due to privacy
considerations MUST include a Privacy header with a priv-value(s) of considerations MUST include a Privacy header with a priv-value(s) of
"header" or "history." A UAC that wants to ensure that privacy not "header" or "history". A UAC that wants to ensure that privacy not
be applied to its identity MUST include a Privacy header with a priv- be applied to its identity MUST include a Privacy header with a priv-
value of "none." value of "none".
In the case where a UAC receives a 3xx response with a Contact header In the case where a UAC receives a 3xx response with a Contact header
and sends a new request in response to it, the UAC MAY include in the and sends a new request in response to it, the UAC MAY include in the
outgoing request the previous hi-entry(s) received in the response. outgoing request the previous hi-entry(s) received in the response.
In this case, the reason header MUST be associated with the hi- In this case, the reason header MUST be associated with the hi-
targeted-to-uri in the previous (last) hi-entry, as described in targeted-to-uri in the previous (last) hi-entry, as described in
Section 6.3.3. A new hi-entry MUST then be added for the URI from Section 7.3.2. A new hi-entry MUST then be added for the URI from
the Contact header (which becomes the new Request-URI). An index the Contact header (which becomes the new Request-URI). An index
MUST be added to the hi-entry. The value for the index is determined MUST be added to the hi-entry. The value for the index is determined
by reading and incrementing the value of the index from the previous following the rules for "Retargeting based upon a Response" as
hi-entry, thus following the same rules as those prescribed for a prescribed in Section 7.3.3. If the Contact header contained any of
proxy in retargeting, described in Section 6.3.4. If the URI in the the header parameter fields defined in this specification, the UAC
Contact header contains a "hit" URI parameter, the UAC MUST add a MUST include the header parameter field as a header parameter field
target parameter to the hi-entry and MUST remove the URI parameter as associated with the current hi-entry as described in Section 7.3.4.
described in Section 6.3.5.
Prior to any application usage of the information by the UAC (e.g.,
debug), the validity SHOULD be ascertained. The entries SHOULD be
evaluated to determine gaps in indices, which could indicate that an
entry has been maliciously removed. Either way, an application
SHOULD be aware of potentially missing information. The
interpretation of the information in the History-Info header by a UAC
in a request depends upon the specific applications supported by the
UAC. Application considerations and guidelines are provided in
section 7.
4.2. User Agent Server (UAS) Behavior 5.2. User Agent Server (UAS) Behavior
4.2.1. Processing of Requests with History-Info 5.2.1. Processing of Requests with History-Info
Once the request terminates at the UAS, the UAS evaluates the Once the request terminates at the UAS, the UAS evaluates the
History-Info header. The last hi-entry reflects the most recent History-Info header. The last hi-entry reflects the most recent
target and SHOULD contain the Request-URI for the received request. target and MUST contain the Request-URI for the received request,
If the Request-URI of the incoming request does not match the last unless the previous entity that forwarded the request does not
hi-entry (e.g., the last proxy does not support History-Info), the support the History-Info header. If the Request-URI of the incoming
UAS MUST insert an hi-entry. The UAS MUST set the hi-targeted-to-uri request does not match the last hi-entry (e.g., the last proxy does
based to the value of Request-URI in the incoming request, unless not support History-Info), the UAS MUST insert an hi-entry. The UAS
privacy is required. If privacy is required, the procedures of MUST set the hi-targeted-to-uri based to the value of Request-URI in
Section 6.3.2 MUST be used. The UAS MUST include an hi-index the incoming request. If privacy is required, a privacy header with
attribute as described in Section 6.3.4. The UAS MUST NOT include a a value of "history" MUST be added to the hi-entry. The UAS MUST
hi-target attribute, since the UAS has no way to know the mechanism include an hi-index attribute as described in Section 7.3.3. The UAS
by which the Request-URI was determined. The addition of the missing MUST NOT include a hi-target attribute, since the UAS has no way to
hi-entry ensures that the most complete information can be provided know the mechanism by which the Request-URI was determined. The
in the response and provides consistency in the information presented addition of the missing hi-entry ensures that the most complete
to applications. The information can also be useful for information can be provided in the response and provides consistency
implementations with B2BUAs that include the History-Info, received in the information presented to applications. The information can
in the incoming request, in the subsequent outgoing request. also be useful for implementations with B2BUAs that include the
History-Info, received in the incoming request, in the outgoing
request.
Prior to any application usage of the information, the validity Prior to any application usage of the information, the validity MUST
SHOULD be ascertained. The entries SHOULD be evaluated to determine be ascertained. If gaps are detected, this MUST NOT be treated as an
gaps in indices, which could indicate that an entry has been error since gaps are possible if the request is forwarded through
maliciously removed. Either way, an application SHOULD be aware of intermediate entities that do not support the History-Info header.
potentially missing information. The interpretation of the The interpretation of the information in the History-Info header by a
information in the History-Info header by a UAS in a request depends UAS in a request depends upon the specific applications supported by
upon the specific applications supported by the UAS. Application the UAS; an application might need to provide special handling in
considerations and guidelines are provided in section 7. some cases where there are gaps. Application considerations and
guidelines are provided in section 7.
4.2.2. Generation of Responses with History-Info 5.2.2. Generation of Responses with History-Info
If the "histinfo" option tag is received in a request, the UAS MUST If the "histinfo" option tag is received in a request, the UAS MUST
include any History-Info received in the request in the subsequent include any History-Info received in the request in the subsequent
response. If privacy is required, entries MUST be anonymized using response. If privacy is required, entries MUST be anonymized as
[RFC3323]. The UAS MUST follow the rules for a redirect server per described in Section 7.3.1. The UAS MUST follow the rules for a
Section 4.3 in generating a 3xx response. redirect server per Section 5.3 in generating a 3xx response.
The processing of History-Info in responses follows the methodology The processing of History-Info in responses follows the methodology
described in Section 16.7 of [RFC3261], with the processing of described in Section 16.7 of [RFC3261], with the processing of
History-Info headers adding an additional step, just before Step 9, History-Info headers adding an additional step, just before Step 9,
"Forwarding the Response". "Forwarding the Response".
4.3. Redirect Server Behavior 5.3. Redirect Server Behavior
A redirect server MUST include the History-Info headers received in A redirect server MUST include the History-Info headers received in
the request in the 3XX response that it sends. A redirect server the request in the 3XX response that it sends. A redirect server
MUST NOT add any new History-Info entries. In order to provide the MUST add any new History-Info entries in cases of retargeting (both
necessary information to populate the target parameter for the new internal and to other SIP entities) in the same manner as prescribed
History-Info entries as a request is redirected, the redirect server for a proxy Section 6. In generating the Contact header in the 3xx
MUST add a "hit" URI parameter to the URIs in the contact header. response, the redirect server MUST add the appropriate target header
The appropriate values for this parameter are described in field parameter to each Contact header as described in Section 7.3.4.
Section 6.3.1.
5. Proxy Behavior 6. Proxy Behavior
The specific processing by proxies for adding the History-Info This section describes the procedures for proxies and other SIP
headers in SIP requests and responses is described in this section. intermediaries for adding History-Info headers when requests are
retargeted.
5.1. Adding the History-Info Header to Requests 6.1. Adding the History-Info Header to Requests
This section describes the process of adding the History-Info header This section describes the process of adding the History-Info header
to requests for the following cases: to requests for the following cases:
o Forwarding of initial request (see Section 5.1.1) o Forwarding of initial request (see Section 6.1.1)
o Resending based on failure response (see Section 5.1.2) o Resending based on failure response (see Section 6.1.2)
o Resending based on redirection response (see Section 5.1.3) o Resending based on redirection response (see Section 6.1.3)
Retargeting is an iterative process, i.e., a proxy may redirect Retargeting is an iterative process, i.e., a proxy may redirect
"internally " more than one time. A typical example would be a proxy "internally " more than one time. A typical example would be a proxy
that redirects a request first to a different user (i.e., it maps to that retargets a request first to a different user (i.e., it maps to
a different AOR), and then forwards to a registered contact bound to a different AOR), and then forwards to a registered contact bound to
that new AOR. A proxy that uses such mechanism SHOULD add multiple that new AOR. In these cases, a proxy MUST add multiple hi-entry
hi-entry fields (e.g., bob@example.com to office@example.com to fields. For example, a proxy that retargets bob@example.com to
office@192.0.2.5) to provide a logical description of the retargeting office@example.com and then to office@192.0.2.5 adds hi-entries for
process. A Reason MAY be associated with the hi-targeted-to-uri that both office@example.com and office@192.0.2.5, in order to provide a
has been retargeted as shown in the example in Appendix B.1. logical description of the retargeting process internal to the proxy.
A Reason MAY be associated with the hi-targeted-to-uri that has been
retargeted as shown in the example in Appendix B.1.
5.1.1. Initial Request 6.1.1. Initial Request
Upon receipt of an initial request for a dialog, or a standalone Upon receipt of an initial request for a dialog, or a standalone
request, a proxy forwarding the request MUST perform the following request, a proxy forwarding the request MUST perform the following
steps. Note that those steps below do not apply if the request is steps. Note that those steps below do not apply if the request is
being re-sent as a result of failure (i.e., timeout, reception of an being re-sent as a result of failure (i.e., timeout, reception of an
error response), or redirection caused by receipt of a 3XX message). error response).
Step 1: Adding Entries on Behalf of Previous Hops Step 1: Adding Entries on Behalf of Previous Hops
If an incoming request does not already have a History-Info header If an incoming request does not already have a History-Info header
field (e.g., the UAC does not include any History-Info header and field (e.g., the UAC does not include any History-Info header and
no proxies in between support History-Info), or if the Request-URI no proxies in between support History-Info), or if the Request-URI
of the incoming request does not match the last hi-entry (e.g., of the incoming request does not match the last hi-entry (e.g.,
the last proxy does not support History-Info), the proxy MUST the last proxy does not support History-Info), the proxy MUST
insert an hi-entry. The proxy MUST set the hi-targeted-to-uri insert an hi-entry. The proxy MUST set the hi-targeted-to-uri
based to the value of Request-URI in the incoming request, unless based to the value of Request-URI in the incoming request, unless
privacy is required. If privacy is required, the procedures of privacy is required. If privacy is required, the procedures of
Section 6.3.2 MUST be used. The proxy MUST NOT include a hi- Section 7.3.1 MUST be used. The proxy MUST NOT include a hi-
target attribute. The proxy MUST include an hi-index attribute as target attribute. The proxy MUST include an hi-index attribute
described in Section 6.3.4. with a value of "1", as described in Section 7.3.3.
Step 2: Tagging URIs in Target Set with "hit" Parameter
The proxy then proceeds to determining the request targets as per
16.5/[RFC3261]. The proxy MUST add a "hit" SIP/SIPS URI parameter
for the target URI that are determined based on either of the two
mechanisms as described in Section 6.3.1.
Step 3: Generating New Entries for Each Outgoing Request Step 2: Generating New Entries for Each Outgoing Request
The proxy then proceeds to request forwarding as per 16.6/ The proxy then proceeds to request forwarding as per 16.6/
[RFC3261]. The proxy MUST add a separate hi-entry in each [RFC3261]. The proxy MUST add a separate hi-entry in each
separate outgoing request for each of the current (outgoing) separate outgoing request for each of the current (outgoing)
targets in the target set. The proxy MUST set the hi-targeted-to- targets in the target set. The proxy MUST set the hi-targeted-to-
uri in those separate hi-entry(s) to the value of the Request-URI uri in those separate hi-entry(s) to the value of the Request-URI
of the current (outgoing) request, unless privacy is required. If of the current (outgoing) request, unless privacy is required. If
privacy is required, the procedures of Section 6.3.2 MUST be used. privacy is required, the procedures of Section 7.3.1 MUST be used.
The proxy MUST include an hi-index for each of the separate hi- The proxy MUST include an hi-index for each of the separate hi-
entry(s) as described in Section 6.3.4. If the Request-URI entry(s) as described in Section 7.3.3. The proxy MUST include
contains a "hit" SIP/SIPS URI parameter, the proxy MUST include a the appropriate hi-target header field parameter for each of the
hi-target attribute for each of the separate entry(s) as described separate entry(s) as described in Section 7.3.4, if applicable.
in Section 6.3.5. The proxy MUST remove the "hit" URI parameter
from the Request-URI.
5.1.2. Re-sending based on failure response 6.1.2. Re-sending based on failure response
When re-sending a request as a result of retargeting because of When re-sending a request as a result of retargeting because of
failure (i.e., either reception of error responses or a timeout which failure (i.e., either reception of error responses or a timeout which
is considered to be an implicit 487 error response), the proxy MUST is considered to be an implicit 408 error response), the proxy MUST
perform the following steps: perform the following steps:
Step 1: Including the Entries from Error Responses & Timeouts Step 1: Including the Entries from Error Responses & Timeouts
The proxy MUST build the History-Info header field(s) sent in the The proxy MUST build the History-Info header field(s) sent in the
outgoing request using the aggregate information associated with outgoing request using the aggregate information associated with
the received error responses(s) and timeout(s) for all the the received error responses(s) and timeout(s) for all the
branches that are generating failures, including the header branches that are generating failures, including the header
entries in the order indicated by the indexing (see entries in the order indicated by the indexing (see
Section 6.3.4). If the received error response did not include Section 7.3.3). If the received error response did not include
any History-Info header fields, the proxy MUST use the same any History-Info header fields, the proxy MUST use the same
History-Info header fields that were sent in the outgoing request History-Info header fields that were sent in the outgoing request
that failed to build the outgoing request. that failed to build the outgoing request.
Step 2: Tagging the Last Entries Step 2: Tagging the Last Entries
The proxy then examines the last hi-entry of the History-Info that The proxy then examines the last hi-entry of the History-Info that
was just generated in Step 1 for each one of the branches that was just generated in Step 1 for each one of the branches that
generated failures or timeouts and MUST add a Reason header for generated failures or timeouts and MUST add a Reason header for
each one of those entries as per the procedures of Section 6.3.3. each one of those entries as per the procedures of Section 7.3.2.
Step 3: Generating New Entries for Each Outgoing Requests Step 3: Generating New Entries for Each Outgoing Requests
Same as per Step 3 above for the normal forwarding case Same as per Step 2 above for the normal forwarding case
Section 5.1.1. Section 6.1.1.
5.1.3. Re-sending based on redirection response 6.1.3. Re-sending based on redirection response
When re-sending a request as a result of retargeting because of When re-sending a request as a result of retargeting because of
redirection (i.e., receipt of a 3XX response), the following steps redirection (i.e., receipt of a 3XX response), the following steps
apply: apply:
Step 1: Including Previous Entries Step 1: Including Previous Entries
The proxy MUST include the History-Info header fields that were The proxy MUST include the History-Info header fields that were
sent in the outgoing request that is being redirected. sent in the outgoing request that is being redirected.
Step 2: Tagging the Last Entry Step 2: Tagging the Last Entry
The proxy then examines the last hi-entry of the History-Info that The proxy then examines the last hi-entry of the History-Info that
was just generated in Step 1 and MUST add a Reason header this was just generated in Step 1 and MUST add a Reason header this
entry as per the procedures of Section 6.3.3. entry as per the procedures of Section 7.3.2.
Step 3: Generating New Entries for Each Outgoing Requests Step 3: Generating New Entries for Each Outgoing Requests
Same as per Step 3 for the normal forwarding case Section 5.1.1. Same as per Step 2 for the normal forwarding case Section 6.1.1.
5.2. Sending History-Info in Responses 6.2. Sending History-Info in Responses
A proxy that receives a request with the "histinfo" option tag in the A proxy that receives a request with the "histinfo" option tag in the
Supported header, SHOULD forward captured History-Info in subsequent, Supported header, MUST forward captured History-Info in subsequent,
provisional, and final responses to the request sent by the ultimate provisional, and final responses to the request sent by the ultimate
UAS (see Section 4.2). UAS (see Section 5.2). Any hi-entry containing a Privacy header with
a value of "history" MUST be anonymized prior to a proxy sending a
A proxy MAY anonymize any hi-entry whose domain corresponds to a response with that hi-entry.
domain for which it is responsible (as per [RFC3323]). For example,
a proxy could require that such entries be anonymized when a response
is forwarded to a domain for which the proxy is not responsible.
The processing of History-Info in responses follows the methodology The processing of History-Info in responses follows the methodology
described in Section 16.7 of [RFC3261], with the processing of described in Section 16.7 of [RFC3261], with the processing of
History-Info headers adding an additional step, just before Step 9, History-Info headers adding an additional step, just before Step 9,
"Forwarding the Response". "Forwarding the Response".
6. The History-Info header field 7. The History-Info header field
6.1. Definition 7.1. Definition
History-Info is a header field as defined by [RFC3261]. "It may History-Info is a header field as defined by [RFC3261]. It may
appear in any initial request for a dialog, standalone request or appear in any initial request for a dialog, standalone request or
responses associated with these requests. For example, History-Info responses associated with these requests. For example, History-Info
may appear in INVITE, REGISTER, MESSAGE, REFER, OPTIONS, SUBSCRIBE, may appear in INVITE, REGISTER, MESSAGE, REFER, OPTIONS, SUBSCRIBE,
and PUBLISH and any valid responses, plus NOTIFY requests that and PUBLISH and any valid responses, plus NOTIFY requests that
initiate a dialog. initiate a dialog.
The History-Info header carries the following information, with the The History-Info header carries the following information when the
mandatory parameters required when the header is included in a header is included in a request or response:
request or response:
o Targeted-to-URI (hi-targeted-to-uri): A mandatory parameter for o Targeted-to-URI (hi-targeted-to-uri): A mandatory parameter for
capturing the Request-URI for the specific request as it is capturing the Request-URI for the specific request as it is
forwarded. forwarded.
o Index (hi-index): A mandatory parameter for History-Info o Index (hi-index): A mandatory parameter for History-Info
reflecting the chronological order of the information, indexed to reflecting the chronological order of the information, indexed to
also reflect the forking and nesting of requests. The format for also reflect the forking and nesting of requests. The format for
this parameter is a string of digits, separated by dots to this parameter is a string of digits, separated by dots to
indicate the number of forward hops and retargets. This results indicate the number of forward hops and retargets. This results
in a tree representation of the history of the request, with the in a tree representation of the history of the request, with the
lowest-level index reflecting a branch of the tree. By adding the lowest-level index reflecting a branch of the tree. By adding the
new entries in order (i.e., following existing entries per the new entries in order (i.e., following existing entries per the
details in Section 5.1), including the index and securing the details in Section 6.1), including the index and securing the
header, the ordering of the History-Info headers in the request is header, the ordering of the History-Info headers in the request is
assured (SEC-req-2, see Appendix A.1). In addition, applications assured (SEC-req-2, see Appendix A.1). In addition, applications
may extract a variety of metrics (total number of retargets, total may extract a variety of metrics (total number of retargets, total
number of retargets from a specific branch, etc.) based upon the number of retargets from a specific branch, etc.) based upon the
index values. index values.
o Reason: An optional parameter for History-Info, reflected in the o Reason: An optional parameter for History-Info, reflected in the
History-Info header by including the Reason Header [RFC3326] History-Info header by including the Reason Header [RFC3326]
escaped in the hi-targeted-to-uri. A reason is included for the escaped in the hi-targeted-to-uri. A reason is included for the
hi-targeted-to-uri that was retargeted as opposed to the hi- hi-targeted-to-uri that was retargeted as opposed to the hi-
skipping to change at page 15, line 23 skipping to change at page 15, line 45
o Privacy: An optional parameter for History-Info, reflected in the o Privacy: An optional parameter for History-Info, reflected in the
History-Info header field values by including the Privacy Header History-Info header field values by including the Privacy Header
[RFC3323] escaped in the hi- targeted-to-uri or by adding the [RFC3323] escaped in the hi- targeted-to-uri or by adding the
Privacy header to the request. The latter case indicates that the Privacy header to the request. The latter case indicates that the
History-Info entries for the domain MUST be anonymized prior to History-Info entries for the domain MUST be anonymized prior to
forwarding, whereas the use of the Privacy header escaped in the forwarding, whereas the use of the Privacy header escaped in the
hi-targeted-to-uri means that a specific hi-entry MUST be hi-targeted-to-uri means that a specific hi-entry MUST be
anonymized. anonymized.
o Target (hi-target): An optional parameter for the History-Info o Target (hi-target): An optional parameter for the History-Info and
header. This parameter is added if the URI to which the outgoing Contact headers. The hi-target is added for a hi-entry when it is
request is targeted contains a "hit" URI parameter Section 6.3.1. first added in a History-Info header field, and only one value is
The hi-target is added for a hi-entry when it is first added in a permitted. Upon receipt of a request or response containing the
History-Info header field, and only one value is permitted. Upon History-Info header, a UA can determine the mechanism by which the
receipt of a request or response containing the History-Info target was determined. The following header field parameters are
header, a UA can determine the mechanism by which the target was defined for this parameter:
determined. The following attributes are defined for this
parameter derived from the values of the "hit" URI parameter:
* "rc": The hi-target is set to "rc" if the "hit" URI parameter "rc": The hi-targeted-to-URI is a contact for the Request-URI,
is set to a value of "rc". in the incoming request, that is bound to an AOR in an abstract
location service. The AOR-to-contact binding has been placed
into the location service by a SIP Registrar that received a
SIP REGISTER request. The "rc" header field parameter contains
the index of the hi-entry associated with the URI in the
incoming request.
* "mp": The hi-target is set to "mp" if the "hit" URI parameter "mp": The hi-targeted-to-URI represents a user other than the
is set to a value of "mp".The "mp" attribute in the hi-target user associated with the Request-URI in the incoming
parameter includes the index parameter for the hi-targeted-to- requesting. This occurs when a request is to be statically or
uri that was retargeted, thus identifying the "mapped from" dynamically retargeted to another user. The value of the "mp"
target. header field parameter is the index parameter for the hi-
targeted-to- uri that was retargeted, thus identifying the
"mapped from" target.
o Extension (hi-extension): A parameter to allow for future optional o Extension (hi-extension): A parameter to allow for future optional
extensions. As per [RFC3261], any implementation not extensions. As per [RFC3261], any implementation not
understanding an extension should ignore it. understanding an extension MUST ignore it.
The following summarizes the syntax of the History-Info header, based The ABNF syntax for the History-Info header is defined as follows:
upon the standard SIP syntax [RFC3261]:
History-Info = "History-Info" HCOLON hi-entry *(COMMA hi-entry) History-Info = "History-Info" HCOLON hi-entry *(COMMA hi-entry)
hi-entry = hi-targeted-to-uri *(SEMI hi-param) hi-entry = hi-targeted-to-uri *(SEMI hi-param)
hi-targeted-to-uri = name-addr hi-targeted-to-uri = name-addr
hi-param = hi-index / hi-target / hi-extension hi-param = hi-index / hi-target / hi-extension
hi-index = "index" EQUAL 1*DIGIT *("." 1*DIGIT) index-val = 1*DIGIT *("." 1*DIGIT)
hi-target = "rc" / mp-param
mp-param = "mp" EQUAL 1*DIGIT *("." 1*DIGIT) hi-index = "index" EQUAL index-val
hi-extension = generic-param hi-target = rc-param / mp-param
The following rules apply: rc-param = "rc" EQUAL index-val
o There MUST be exactly one hi-index parameter per hi-entry. mp-param = "mp" EQUAL index-val
o There MUST be no more than one hi-target parameter. hi-extension = generic-param
o There MAY be any number of hi-extension parameters. The ABNF definitions for "generic-param" and "name-addr" are from
[RFC3261].
o The ABNF definitions for "generic-param" and "name-addr" are from Note that since both the Reason and Privacy parameters are escaped in
[RFC3261]. the hi-targeted-to-uri, these fields will not be available in the
case that the hi-targeted-to-uri is a Tel-URI [RFC3966].
6.2. Examples 7.2. Examples
The following provides some examples of the History-Info header. The following provides some examples of the History-Info header.
Note that the backslash and CRLF between the fields in the examples Note that the backslash and CRLF between the fields in the examples
below are for readability purposes only. below are for readability purposes only.
History-Info: <sip:UserA@ims.example.com>;index=1;foo=bar History-Info: <sip:UserA@ims.example.com>;index=1;foo=bar
History-Info: <sip:UserA@ims.example.com?Reason=SIP%3B\ History-Info: <sip:UserA@ims.example.com?Reason=SIP%3B\
cause%3D302>;index=1.1,\ cause%3D302>;index=1.1,\
<sip:UserB@example.com?Privacy=history&Reason=SIP%3B\ <sip:UserB@example.com?Privacy=history&Reason=SIP%3B\
cause%3D486>;index=1.2;mp=1.1,\ cause%3D486>;index=1.2;mp=1.1,\
<sip:45432@192.168.0.3>;index=1.3;rc <sip:45432@192.168.0.3>;index=1.3;rc=1.2
6.3. Procedures 7.3. Procedures
The following sections define procedures for processing of the The following sections define procedures for processing of the
History-Info header and the "hit" SIP/SIPS URI parameter and Privacy parameters (and headers) associated with the History-Info header.
header. These procedures may be applicable to processing entities These procedures may be applicable to processing entities such as
such as Proxies, Redirect Servers or User Agents. Proxies, Redirect Servers or User Agents.
6.3.1. SIP/SIPS URI target parameter for History-Info Header
This specification defines a new SIP/SIPS URI Parameter indicating
the mechanism by which a new target for a request is determined.
This parameter is added to the SIP/SIPS URIs as they are added to the
target set per the procedures of 16.5 [RFC3261]] or by a redirect
server as it populates the Contact header for a 3xx response. This
parameter is used to populate the hi-target parameter Section 6.3.5
when a Request-URI is first added in a hi-entry in the History-Info
header field. This parameter MUST be removed from the URI when the
hi-entry is constructed.
The following two values are defined for this URI parameter:
o "rc": The Request-URI is a contact that is bound to an AOR in an
abstract location service. The AOR-to-contact binding has been
placed into the location service by a SIP Registrar that received
a SIP REGISTER request.
o "mp": The Request-URI is a URI that represents another user. This
occurs when a request is to be statically or dynamically
retargeted to another user.
The following defines the ABNF for the "hit" URI parameter:
hit-param = "hit=" ("rc" / "mp")
6.3.2. Privacy in the History-Info Header 7.3.1. Privacy in the History-Info Header
The privacy requirements for this document are described in The privacy requirements for this document are described in
Appendix A.2. Appendix A.2.
The History-Info header can inadvertently reveal information about As with other SIP headers described in [RFC3323], the History-Info
the requestor as described in [RFC3323]. The Privacy header is used header can inadvertently reveal information about the originator. A
to ensure the privacy requirements are satisfied for both the value of "header" in the Privacy header is used to indicate that such
History-Info entries received by the intermediary in the incoming headers in the request be privacy protected when the request is
request (per PRIV-req-2 in Appendix A.2) and the History-Info entries forwarded by the intermediary. A value of "history" in the Privacy
that are added by the intermediary as the request is retargeted per header indicates that the History-Info header should be privacy
PRIV-req-1 in Appendix A.2. If the requestor has indicated a priv- protected. If there is a Privacy header in the request with a priv-
value of "session" or "header" in the request, all History-Info value of "header" or "history", then the initial hi-entry MUST be
entries MUST be anonymized when the request leaves a domain for which anonymized and the header removed when the request leaves a domain
the intermediary is responsible. for which the SIP entity is responsible.
Privacy can also be associated with a specific History-Info entry,
and any entry that corresponds to that same user rather than all
History-Info entries in a request. For example, if Alice sends a
request to Bob without any privacy, and Bob redirects to Carol with
privacy setup for himself, Carol should receive a request where
Alice's history information is present, but Bob's has been
anonymized. This is accomplished by adding a new priv-value,
history, to the Privacy header [RFC3323] indicating that a specific
History-Info header entry can not be forwarded outside the domain.
In addition, the History-Info header can reveal general routing
information which may be viewed by a specific intermediary or
network. Thus, a proxy can use local policy to determine whether the
History-Info header entries for it's whole domain are private or not
when exiting the domain through retargeting (PRIV-req-3).
It is recognized that satisfying the privacy requirements can impact
the functionality of this solution by overriding the request to
generate the information. Thus, the following recommendations are
made to ensure optimal functionality without compromising privacy:
If there is a Privacy header in the request with a priv-value of In addition, the History-Info header can reveal general routing and
"session", "header", or "history", an hi-entry SHOULD be added if diverting information within an intermediary, which the intermediary
the request is being retargeted to a URI associated with a domain may want to privacy protect. In this case, a value of "history" in
for which the processing entity is responsible. If there is no the Privacy header is used to indicate which History-Info header
Privacy header, but the processing entity's local policies entries added by a SIP entity are to be anonymized. The priv-value
indicate that the hi-entry(s) cannot be forwarded beyond the of "history" MUST be in the privacy header escaped in the hi-
domain for which this intermediary is responsible, then a Privacy targeted-to-uri for each hi-entry, added by the SIP entity, as the
header with a priv-value of "history" SHOULD be associated with request is retargeted within the domain for which the SIP entity is
each hi-entry added by the proxy as the request is forwarded responsible. If a request is being retargeted to a URI associated
within the domain. with a domain for which the SIP entity is not responsible, the
processing entity MUST anonymize the hi-entries with a priv-value of
"history" and MUST remove the Privacy header from the hi-entries
prior to forwarding, unless the processing entity knows a priori that
it can rely on a downstream processing entity to apply the requested
privacy. The mechanism for the latter functionality is outside the
scope of this specification.
If a request is being retargeted to a URI associated with a domain Finally, the terminator of the request may not want to reveal the
for which the processing identity is not responsible and there is final reached target to the originator. In this case, the terminator
a Privacy header in the request with a priv-value of "session", uses the a value of "history" in the Privacy header in the last hi-
"header", or "history", the processing entity MUST anonymize hi- entry in the response. The SIP entity that forwards the response
entry(s) as per [RFC3323] prior to forwarding, unless the MUST anonymize that hi-entry and remove the Privacy header.
processing entity knows a priori that it can rely on a downstream
processing entity within its domain to apply the requested privacy
or local policy allows the forwarding.
6.3.3. Reason in the History-Info Header 7.3.2. Reason in the History-Info Header
For retargets that are the result of an explicit SIP response, a For retargets that are the result of an explicit SIP response, a
Reason MUST be associated with the hi-targeted-to-uri. If the SIP Reason MUST be associated with the hi-targeted-to-uri. If the SIP
response does not include a Reason header (see [RFC3326]), the SIP response does not include a Reason header (see [RFC3326]), the SIP
Response Code that triggered the retargeting MUST be included as the Response Code that triggered the retargeting MUST be included as the
Reason associated with the hi-targeted-to-uri that has been Reason associated with the hi-targeted-to-uri that has been
retargeted. If the response contains a Reason header for a protocol retargeted. If the response contains a Reason header for a protocol
that is not SIP (e.g., Q.850), it MUST be captured as an additional that is not SIP (e.g., Q.850), it MUST be captured as an additional
Reason associated with the hi-targeted-to-uri that has been Reason associated with the hi-targeted-to-uri that has been
retargeted, along with the SIP Response Code. If the Reason header retargeted, along with the SIP Response Code. If the Reason header
is a SIP reason, then it MUST be used as the Reason associated with is a SIP reason, then it MUST be used as the Reason associated with
the hi-targeted-to-uri rather than the SIP response code. the hi-targeted-to-uri rather than the SIP response code.
If a request has timed out (instead of being explicitly rejected), it If a request has timed out (instead of being explicitly rejected), it
SHOULD be treated as if a 487 "Request Terminated" error response MUST be treated as if a 408 "Request Terminated" error response code
code was received. was received.
6.3.4. Indexing in the History-Info Header 7.3.3. Indexing in the History-Info Header
In order to maintain ordering and accurately reflect the nesting and In order to maintain ordering and accurately reflect the nesting and
retargeting of the request, an index MUST be included along with the retargeting of the request, an index MUST be included along with the
Targeted-to-URI being captured. Per the syntax in Section 6, the Targeted-to-URI being captured. Per the syntax in Section 7, the
index consists of a dot-delimited series of digits (e.g., 1.1.2). index consists of a dot-delimited series of digits (e.g., 1.1.2).
Each dot reflects a hop or level of nesting; thus, the number of hops Each dot reflects a hop or level of nesting; thus, the number of hops
is determined by the total number of dots. Within each level, the is determined by the total number of dots. Within each level, the
integer reflects the number of peer entities to which the request has integer reflects the number of peer entities to which the request has
been routed. Thus, the indexing results in a logical tree been routed. Thus, the indexing results in a logical tree
representation for the history of the request. For each level of representation for the history of the request.
indexing, the index MUST start at 1. An increment of 1 MUST be used
for advancing to a new branch. The first entry MUST be set to 1. The first index in a series of History-Info entries MUST be set to 1.
In the case that a proxy adds an entry on behalf of the previous hop,
the index MUST be set to 1. For each level of indexing, the index
MUST start at 1. An increment of 1 MUST be used for advancing to a
new branch.
The basic rules for adding the index are summarized as follows: The basic rules for adding the index are summarized as follows:
1. Basic Forwarding: In the case of a request that is being 1. Basic Forwarding: In the case of a request that is being
forwarded, the index is determined by adding another sub-level of forwarded, the index is determined by adding another sub-level of
indexing since the depth/length of the branch is increasing. To indexing since the depth/length of the branch is increasing. To
accomplish this, the processing entity reads the value from the accomplish this, the processing entity MUST read the value from
History-Info header in the received request, if available, and the History-Info header in the received request and MUST add
adds another level of indexing by appending the dot delimiter another level of indexing by appending the dot delimiter followed
followed by an initial index for the new level of 1. For by an initial index for the new level of 1. For example, if the
example, if the index in the last History-Info header field in index in the last History-Info header field in the received
the received request is 1.1, this proxy would initialize its request is 1.1, this proxy would initialize its index to 1.1.1
index to 1.1.1 and forward the request. and forward the request.
2. Retargeting within a processing entity - 1st instance: For the 2. Retargeting within a processing entity - 1st instance: For the
first instance of retargeting within a processing entity, the first instance of retargeting within a processing entity, the
calculation of the index follows that prescribed for basic calculation of the index follows that prescribed for basic
forwarding. forwarding.
3. Retargeting within a processing entity - subsequent instance: For 3. Retargeting within a processing entity - subsequent instance: For
each subsequent retargeting of a request by the same processing each subsequent retargeting of a request by the same processing
entity, another branch is added. With the index for each new entity, another branch MUST be added. The index for each new
branch calculated by incrementing the last/lowest digit at the branch MUST be calculated by incrementing the last/lowest digit
current level, the index in the next request forwarded by this at the current level, the index in the next request forwarded by
same processing entity, following the example above, would be this same processing entity, following the example above, would
1.1.2. be 1.1.2.
4. Retargeting based upon a Response: In the case of retargeting due 4. Retargeting based upon a Response: In the case of retargeting due
to a specific response (e.g., 302), the index would be calculated to a specific response (e.g., 302), the index MUST be calculated
per rule 3. That is, the lowest/last digit of the index is per rule 3. That is, the lowest/last digit of the index MUST be
incremented (i.e., a new branch is created), with the increment incremented (i.e., a new branch is created), with the increment
of 1. For example, if the index in the History-Info header of of 1. For example, if the index in the History-Info header of
the received request was 1.2, then the index in the History-Info the sent request is 1.2 and the response to the request is a 302,
header field for the new hi-targeted- to-URI would be 1.3. then the index in the History-Info header field for the new hi-
targeted- to-URI would be 1.3.
5. Forking requests: If the request forwarding is done in multiple 5. Forking requests: If the request forwarding is done in multiple
forks (sequentially or in parallel), the index MUST be captured forks (sequentially or in parallel), the index MUST be captured
for each forked request per the rules above, with each new for each forked request per the rules above, with each new
request having a unique index. Each index are sequentially request having a unique index. Each index MUST be sequentially
assigned. For example, if the index in the last History-Info assigned. For example, if the index in the last History-Info
header field in the received request is 1.1, this processing header field in the received request is 1.1, this processing
entity would initialize its index to 1.1.1 for the first fork, entity would initialize its index to 1.1.1 for the first fork,
1.1.2 for the second, and so forth (see Figure 1 for an example). 1.1.2 for the second, and so forth (see Figure 1 for an example).
Note that for each individual fork, only the entry corresponding Note that for each individual fork, only the entry corresponding
that that fork is included (e.g., the entry for fork 1.1.1 is not to that fork is included (e.g., the entry for fork 1.1.1 is not
included in the request sent to fork 1.1.2, and vice-versa). included in the request sent to fork 1.1.2, and vice-versa).
6. When a response is built and it represents the aggregate of 6. When a response is built and it represents the aggregate of
multiple forks (e.g., multiple forks that fail), the processing responses to multiple forks (e.g., multiple forks that fail), the
entity builds the subsequent response using the aggregated processing entity MUST build the subsequent response using the
information associated with each of those forks and including the aggregated information associated with each of the forks for
header entries in the order indicated by the indexing. For which there have been responses and MUST include the header
example, if a procesing entity received failure responses for entries in the order indicated by the indexing. For example, if
forks 1.1.1 and 1.1.2, it would forward both the 1.1.1 and 1.1.2 a procesing entity received failure responses for forks 1.1.1 and
entries to 1.1. See Appendix B.1 for an example. Responses are 1.1.2, it would return both the 1.1.1 and 1.1.2 entries to the
entity that generated the hi-entry with index of 1. See
Appendix B.1 for an example. Note that in the case of parallel
forking where one fork is successful, only the forks for which
responses have been received at the time the proxy sends the
successful response are included in that response. Responses are
processed as described in Section 16.7 of [RFC3261] with the processed as described in Section 16.7 of [RFC3261] with the
aggregated History-Info entries processed similar to Step 7 aggregated History-Info entries processed similar to Step 7
"Aggregate Authentication Header Field Values". "Aggregate Authentication Header Field Values".
6.3.5. Request Target in the History-Info Header 7.3.4. Request Target in the History-Info Header
The hi-target attribute MUST be added to the History-Info header if This specification defines two header field parameters, "rc" and
the target to which the request is being forwarded contains a "hit" "mp", indicating two non-inclusive mechanisms by which a new target
URI parameter as defined in Section 6.3.1. for a request is determined. The specific parameter field to be
included in the History-Info header is determined as the targets are
added to the target set per the procedures of 16.5 or when the
Contact header field in a 3xx response is populated. Both parameters
contain an index whose value corresponds to the index in the hi-entry
containing the Request-URI that was retargeted.
If the value of the "hit" parameter is "mp", then the index of the The specific parameter field to be included in the History-Info
entry corresponding to the original target (i.e., the "mapped-from" header is determined as follows:
target) MUST be added as a parameter to "mp".
7. Application Considerations o "rc": If the hi-targeted-to-URI was determined based on a contact
for the Request-URI being retargeted that is bound to an AOR in an
abstract location service, then the "rc" header field parameter
MUST be included in the hi-entry. The index of the "rc" parameter
MSUT be set to the hi-index containing the Request-URI being
retargeted.
o "mp": If the hi-targeted-to-URI was determined based on a mapping
to a user other than the user associated with the Request-URI
being retargeted, then the "mp" header field parameter MUST be
included in the hi-entry. The index of the "mp" parameter MUST be
set to the hi-index containing the Request-URI being retargeted.
Note that there are two scenarios by which the "mp" parameter can be
derived.
o The mapping was done by the receiving entity on its own authority,
in which case the mp-value is the parent index of the hi-entry's
index.
o The mapping was done due to receiving a 3xx response, in which
case the mp-value is an earlier sibling of the hi-entry's index,
that of the downstream request which received the 3xx response.
8. Application Considerations
History-Info provides a very flexible building block that can be used History-Info provides a very flexible building block that can be used
by intermediaries and UAs for a variety of services. The following by intermediaries and UAs for a variety of services. Prior to any
summarizes the categories of information that applications may use: application usage of the information the entries MUST be evaluated to
determine gaps in indices. If gaps are detected, this MUST NOT be
treated as an error since gaps are possible if the request is
forwarded through intermediate entities that do not support the
History-Info header. The interpretation of the information in the
History-Info header depends upon the specific application; an
application might need to provide special handling in some cases
where there are gaps.
The following summarizes the categories of information that
applications may use:
1. Complete history information - e.g., for debug or other 1. Complete history information - e.g., for debug or other
operational and management aspects, optimization of determining operational and management aspects, optimization of determining
targets to avoid retargeting to the same URI, etc. This targets to avoid retargeting to the same URI, etc. This
information is relevant to proxies, UACs and UASs. information is relevant to proxies, UACs and UASs.
2. Entry prior to last entry with hi-target of "rc" in the Request 2. Entry with the index that matches the value of the last entry
received by a UAS - i.e., the Request URI associated with the with a "rc" header parameter in the Request received by a UAS -
destination of the request was determined based on a Registered i.e., the Request URI associated with the destination of the
Contact. request was determined based on an AOR-to-contact binding in an
abstract location service.
3. Entry with the index that matches the value of the last entry 3. Entry with the index that matches the value of the last entry
with a "mp" hi-target parameter in the Request received by a UAS with a "mp" header parameter in the Request received by a UAS -
- i.e., the last Request URI that was mapped to reach the i.e., the last Request URI that was mapped to reach the
destination. destination.
4. Entry prior to first entry with hi-target of "rc" in the Request 4. Entry with the index that matches the value of the first entry
received by a UAS - i.e., the first Registered Contact to which with a "rc" header parameter in the Request received by a UAS.
the request was targeted. Note, this would be the original AoR if all entries support the
History-Info header and there is absence of a "mp" header
parameter prior to the "rc" header parameter in the History-Info
header. However, there is no guarantee that all entities will
support History-Info, thus the first entry with an "rc" header
parameter within the domain associated with the target URI at the
destination is more likely to be useful.
5. Entry with the index that matches the value of the first entry 5. Entry with the index that matches the value of the first entry
with a "mp" hi-target parameter - i.e., the original target of with a "mp" header parameter in the Request received by a UAS.
the request. Note, this would be the original mapped URI if all entities
supported the History-Info header. However, there is no
guarantee that all entities will support History-Info, thus the
first entry with an "mp" header parameter within the domain
associated with the target URI at the destination is more likely
to be useful.
In many cases, applications are most interested in the information In many cases, applications are most interested in the information
within a particular domain(s), thus only a subset of the information within a particular domain(s), thus only a subset of the information
is required. is required.
Some applications may use multiple types of information. For Some applications may use multiple types of information. For
example, an Automatic Call Distribution (ACD)/Call center application example, an Automatic Call Distribution (ACD)/Call center application
that utilizes the entry prior to the first History-Info entry with an that utilizes the entry who index matches the index of the first
hi-target value of "mp", may also display other agents, reflected by History-Info entry with an hi-target value of "mp", may also display
other History-Info entries prior to entries with hi-target values of other agents, reflected by other History-Info entries prior to
"rc", to whom the call was targeted prior to its arrival at the entries with hi-target values of "rc", to whom the call was targeted
current agent. This could allow the agent the ability to decide how prior to its arrival at the current agent. This could allow the
they might forward or reroute the call if necessary (avoiding agents agent the ability to decide how they might forward or reroute the
that were not previously available for whatever reason, etc.). call if necessary (avoiding agents that were not previously available
for whatever reason, etc.).
Since support for History-Info header is optional, a service MUST Since support for History-Info header is optional, a service MUST
define default behavior for requests and responses not containing define default behavior for requests and responses not containing
History-Info headers. For example, an entity may receive only History-Info headers. For example, an entity may receive only
partial History-Info entries or entries which are not tagged partial History-Info entries or entries which are not tagged
appropriately with an hi-target parameter. This may not impact some appropriately with an hi-target parameter. This may not impact some
applications (e.g., debug), however, it could require some applications (e.g., debug), however, it could require some
applications to make some default assumptions in this case. For applications to make some default assumptions in this case. For
example, in an ACD scenario, the application could select the oldest example, in an ACD scenario, the application could select the oldest
hi-entry with the domain associated with the ACD system and display hi-entry with the domain associated with the ACD system and display
that as the original called party. Depending upon how and where the that as the original called party. Depending upon how and where the
request may have been retargeted, the complete list of agents to whom request may have been retargeted, the complete list of agents to whom
the call was targeted may not be available. the call was targeted may not be available.
8. Security Considerations 9. Security Considerations
The security requirements for this document are specified in The security requirements for this document are specified in
Appendix A.1. Appendix A.1.
This document defines a header for SIP. The use of the Transport This document defines a header for SIP. The use of the Transport
Layer Security (TLS) protocol [RFC5246] as a mechanism to ensure the Layer Security (TLS) protocol [RFC5246] as a mechanism to ensure the
overall confidentiality of the History-Info headers (SEC-req-4) is overall confidentiality of the History-Info headers (SEC-req-4) is
strongly RECOMMENDED. This results in History-Info having at least strongly RECOMMENDED. This results in History-Info having at least
the same level of security as other headers in SIP that are inserted the same level of security as other headers in SIP that are inserted
by intermediaries. With TLS, History-Info headers are no less, nor by intermediaries. With TLS, History-Info headers are no less, nor
skipping to change at page 22, line 35 skipping to change at page 23, line 26
to define whether it can make use of the information in the case of to define whether it can make use of the information in the case of
missing entries. missing entries.
Note that while using the SIPS scheme (as per [RFC5630]) protects Note that while using the SIPS scheme (as per [RFC5630]) protects
History-Info from tampering by arbitrary parties outside the SIP History-Info from tampering by arbitrary parties outside the SIP
message path, all the intermediaries on the path are trusted message path, all the intermediaries on the path are trusted
implicitly. A malicious intermediary could arbitrarily delete, implicitly. A malicious intermediary could arbitrarily delete,
rewrite, or modify History-Info. This specification does not attempt rewrite, or modify History-Info. This specification does not attempt
to prevent or detect attacks by malicious intermediaries. to prevent or detect attacks by malicious intermediaries.
9. IANA Considerations 10. IANA Considerations
This document requires several IANA registrations detailed in the This document requires several IANA registrations detailed in the
following sections. following sections.
This document updates [RFC4244] but uses the same SIP header field This document updates [RFC4244] but uses the same SIP header field
name and option tag. The IANA registry needs to update the name and option tag. The IANA registry needs to update the
references to [RFC4244] with [RFCXXXX]. references to [RFC4244] with [RFCXXXX].
9.1. Registration of New SIP History-Info Header 10.1. Registration of New SIP History-Info Header
This document defines a SIP header field name: History-Info and an This document defines a SIP header field name: History-Info and an
option tag: histinfo. The following changes have been made to option tag: histinfo. The following changes have been made to
http:///www.iana.org/assignments/sip-parameters The following row has http:///www.iana.org/assignments/sip-parameters The following row has
been added to the header field section:. been added to the header field section:.
The following row has been added to the header field section: The following row has been added to the header field section:
Header Name Compact Form Reference Header Name Compact Form Reference
----------- ------------ --------- ----------- ------------ ---------
skipping to change at page 23, line 27 skipping to change at page 24, line 19
supports the History Information to be supports the History Information to be
captured for requests and returned in captured for requests and returned in
subsequent responses. This tag is not subsequent responses. This tag is not
used in a Proxy-Require or Require used in a Proxy-Require or Require
header field since support of header field since support of
History-Info is optional. History-Info is optional.
Note to RFC Editor: Please replace RFC XXXX with the RFC number of Note to RFC Editor: Please replace RFC XXXX with the RFC number of
this specification. this specification.
9.2. Registration of "history" for SIP Privacy Header 10.2. Registration of "history" for SIP Privacy Header
This document defines a priv-value for the SIP Privacy header: This document defines a priv-value for the SIP Privacy header:
history The following changes have been made to history The following changes have been made to
http://www.iana.org/assignments/sip-priv-values The following has http://www.iana.org/assignments/sip-priv-values The following has
been added to the registration for the SIP Privacy header: been added to the registration for the SIP Privacy header:
Name Description Registrant Reference Name Description Registrant Reference
---- ----------- ---------- --------- ---- ----------- ---------- ---------
history Privacy requested for Mary Barnes [RFCXXXX] history Privacy requested for Mary Barnes [RFCXXXX]
History-Info header(s) mary.barnes@nortel.com History-Info header(s) mary.barnes@polycom.com
Note to RFC Editor: Please replace RFC XXXX with the RFC number of Note to RFC Editor: Please replace RFC XXXX with the RFC number of
this specification. this specification.
9.3. Registration of "hit" SIP/SIPS URI Parameter 10.3. Registration of Header Field Parameters
This specification adds a new value to the IANA registration in the This specification defines the following new SIP header field
"SIP/SIPS URI Parameters" registry, http:/www.iana.org/assignments/ parameters in the SIP Header Field parameter sub-registry in the SIP
sip-parameters, as defined in [RFC3969]. Parameter Registry, http:/www.iana.org/assignments/sip-parameters.
Parameter Name Predefined Values Reference Header Field Parameter Name Predefined Reference
____________________________________________ Values
hit Yes ("rc"/"mp") [RFCxxxx] _____________________________________________________________________
History-Info mp No [RFC xxxx]
History-Info rc No [RFC xxxx]
Contact mp No [RFC xxxx]
Contact rc No [RFC xxxx]
Note to RFC Editor: Please replace RFC XXXX with the RFC number of Note to RFC Editor: Please replace RFC XXXX with the RFC number of
this specification. this specification.
10. Acknowledgements 11. Acknowledgements
Jonathan Rosenberg et al produced the document that provided Jonathan Rosenberg et al produced the document that provided
additional use cases precipitating the requirement for the new additional use cases precipitating the requirement for the new header
"target" parameter in the History-Info header and the new SIP/SIPS parameters to capture the method by which a Request URI is
URI parameter. Ian Elz provided feedback on the privacy aspects. determined. The authors would like to acknowledge the constructive
feedback provided by Ian Elz, Paul Kyzivat, John Elwell, Hadriel
Kaplan and Dale Worley.
Mark Watson, Cullen Jennings and Jon Peterson provided significant Mark Watson, Cullen Jennings and Jon Peterson provided significant
input into the initial work that resulted in the development of of input into the initial work that resulted in the development of of
[RFC4244]. The editor would like to acknowledge the constructive [RFC4244]. The editor would like to acknowledge the constructive
feedback provided by Robert Sparks, Paul Kyzivat, Scott Orton, John feedback provided by Robert Sparks, Paul Kyzivat, Scott Orton, John
Elwell, Nir Chen, Palash Jain, Brian Stucker, Norma Ng, Anthony Elwell, Nir Chen, Palash Jain, Brian Stucker, Norma Ng, Anthony
Brown, Jayshree Bharatia, Jonathan Rosenberg, Eric Burger, Martin Brown, Jayshree Bharatia, Jonathan Rosenberg, Eric Burger, Martin
Dolly, Roland Jesske, Takuya Sawada, Sebastien Prouvost, and Dolly, Roland Jesske, Takuya Sawada, Sebastien Prouvost, and
Sebastien Garcin in the development of [RFC4244]. Sebastien Garcin in the development of [RFC4244].
The editor would like to acknowledge the significant input from Rohan The editor would like to acknowledge the significant input from Rohan
Mahy on some of the normative aspects of the ABNF for [RFC4244], Mahy on some of the normative aspects of the ABNF for [RFC4244],
particularly around the need for and format of the index and around particularly around the need for and format of the index and around
the security aspects. the security aspects.
11. Changes from RFC 4244 12. Changes from RFC 4244
This RFC replaces [RFC4244]. This RFC replaces [RFC4244].
Deployment experience with [RFC4244] over the years has shown a Deployment experience with [RFC4244] over the years has shown a
number of issues, warranting an update: number of issues, warranting an update:
o In order to make [RFC4244] work in "real life", one needs to make o In order to make [RFC4244] work in "real life", one needs to make
"assumptions" on how History-Info is used. For example, many "assumptions" on how History-Info is used. For example, many
implementations filter out many entries, and only leave specific implementations filter out many entries, and only leave specific
entries corresponding, for example, to first and last redirection. entries corresponding, for example, to first and last redirection.
skipping to change at page 25, line 11 skipping to change at page 26, line 8
o [RFC4244] is overly permissive and evasive about recording o [RFC4244] is overly permissive and evasive about recording
entries, causing interoperability issues. entries, causing interoperability issues.
o The examples in the call flows had errors, and confusing because o The examples in the call flows had errors, and confusing because
they often assume "loose routing". they often assume "loose routing".
o [RFC4244] has lots of repetitive and unclear text due to the o [RFC4244] has lots of repetitive and unclear text due to the
combination of requirements with solution. combination of requirements with solution.
o [RFC4244] gratuitly mandates the use of TLS on every hop. No o [RFC4244] gratuitously mandates the use of TLS on every hop. No
existing implementation enforces this rule, and instead, the use existing implementation enforces this rule, and instead, the use
of TLS or not is a general SIP issue, not an [RFC4244] issue per of TLS or not is a general SIP issue, not an [RFC4244] issue per
se. se.
o [RFC4244] does not include clear procedures on how to deliver o [RFC4244] does not include clear procedures on how to deliver
current target URI information to the UAS when the Request-URI is current target URI information to the UAS when the Request-URI is
replaced with a contact. replaced with a contact.
o [RFC4244] does not allow for marking History-Info entries for easy o [RFC4244] does not allow for marking History-Info entries for easy
processing by User Agents. processing by User Agents.
The following summarizes the functional changes between this The following summarizes the functional changes between this
specification and [RFC4244]: specification and [RFC4244]:
1. Added a parameter, "target", to the History-Info header and 1. Added header parameters to capture the specific method by which a
defined a SIP/SIPS URI parameter indicating targets that are target is determined to facilitate processing by users of the
determined by a registered contact or based on mapping the History-Info header entries. A specific header parameter is
incoming Request-URI to another user to facilitate processing at captured for each of the target URIs as the target set is
the UAS. The URI parameter is added to the target URIs as the determined (per section 16.5 of [RFC3261]). The header parameter
target set is determined (per section 16.5 of [RFC3261]) and is used in both the History-Info and the Contact headers.
removed when the "target" parameter is populated, using the URI
parameter value, in the History-Info header (per section 16.6 of
[RFC3261]).
2. Rather than recommending that entries be removed in the case of 2. Rather than recommending that entries be removed in the case of
certain values of the privacy header, recommend that the entries certain values of the privacy header, recommend that the entries
are anonymized. are anonymized.
3. Updated the security section to be equivalent to the security 3. Updated the security section to be equivalent to the security
recommendations for other SIP headers inserted by intermediaries. recommendations for other SIP headers inserted by intermediaries.
The first 2 changes are intended to facilitate application usage of The first 2 changes are intended to facilitate application usage of
the History-Info header and eliminate the need to make assumptions the History-Info header and eliminate the need to make assumptions
based upon the order of the entries and ensure that the most complete based upon the order of the entries and ensure that the most complete
set of information is available to the applications. set of information is available to the applications.
In addition, editorial changes were done to both condense and clarify In addition, editorial changes were done to both condense and clarify
the text, moving the requirements to an appendix. The examples were the text, moving the requirements to an appendix. The examples were
simplified and updated to reflect the protocol changes. Several of simplified and updated to reflect the protocol changes. Several of
the call flows in the appendix were removed and put into a separate the call flows in the appendix were removed and put into a separate
document that includes additional use cases that require the new document that includes additional use cases that require the new
parameters. header parameters.
11.1. Backwards compatibility 12.1. Backwards compatibility
This specification is backwards compatible since [RFC4244] allows for This specification is backwards compatible since [RFC4244] allows for
the addition of new optional parameters. This specification adds an the addition of new optional parameters. This specification adds an
optional parameter "target" to the History-Info header. Entities optional SIP header field parameter to the History-Info and Contact
that have not implemented this specification should ignore this headers. Entities that have not implemented this specification MUST
parameter, however, per [RFC4244] an entity MUST NOT remove this ignore these parameters, however, per [RFC4244] an entity MUST NOT
parameter from an hi-entry. This specification defines a SIP/SIPS remove this parameter from an hi-entry.
URI parameter, "hit". An entity that does not understand the "hit"
URI parameter SHOULD ignore the parameter and MAY remove the
parameter from the URI as it is used as the target for a request.
12. Changes since last Version 13. Changes since last Version
NOTE TO THE RFC-Editor: Please remove this section prior to NOTE TO THE RFC-Editor: Please remove this section prior to
publication as an RFC. publication as an RFC.
Changes from 01 to 02:
1. Editorial nits/clarifications. [Issues: 1,6,17,18,21-
23,25,26,30-33,35-37,39,40]
2. Removing extraneous 4244 text - e.g., errors in flows,
"stronger" security, "session" privacy. [Issues: 3,5,7,11 ]
3. Updated definition of "retarget" to be all encompassing - i.e.,
also includes internal changes of target URI. Clarified text
for "internal retarging" in proxy section. [Issues: 2,8,9]
4. Clarified that the processing for Proxies is equally applicable
to other SIP intermediaries. [Issue: 9].
5. Changed more SHOULDs to MUSTs. [Issue: 10]
6. Fixes to Application considerations section. [Issues: 12-15]
7. Changed language in the procedure for Indexing to normative
language.
8. Clarifications for UAC processing:
* MUST add hi-entry. [Issue: 28]
* Clarify applicability to B2BUA. [Issue: 29]
* Fixed text for indexing for UAC in case of 3xx.
9. Changed "hit" URI parameter to header parameters: [Issues:4,40]
* Added index to all target header parameters. [Issues: 41]
* Updated all the relevant sections documenting setting and use
of new header parameters. [Issue: 40]
10. Updated/clarified privacy handling. [Issue: 16]
11. Updated Redirect Server section to allow adding History-Info
headers. [Issue: 24 ]
12. Added text around restrictions for Tel-URIs - i.e., no privacy
or reason. [Issues: 4, 12]
13. Updated text for forking - what goes in response. [Issues:
19,20]
Changes from 00 to 01: Changes from 00 to 01:
1. Moved examples (except first) in appendix to a new 1. Moved examples (except first) in appendix to a new
(informational) document. (informational) document.
2. Updated UAS and UAC sections to clarify and expand on the 2. Updated UAS and UAC sections to clarify and expand on the
handling of the History-Info header. handling of the History-Info header.
3. Updated the Application considerations section: 3. Updated the Application considerations section:
skipping to change at page 28, line 33 skipping to change at page 30, line 23
5. Reverted proxy response handling text to previous form - just 5. Reverted proxy response handling text to previous form - just
changing the privacy aspects to anonymize, rather than remove. changing the privacy aspects to anonymize, rather than remove.
6. Other editorial changes to condense and simplify. 6. Other editorial changes to condense and simplify.
7. Moved Privacy examples to Appendix. 7. Moved Privacy examples to Appendix.
8. Added forking to Basic call example. 8. Added forking to Basic call example.
Changes from barnes-sipcore-4244bis-00 to 01 :
1. Clarified "retarget" definition.
2. Removed privacy discussion from optionality section - just refer
to privacy section.
3. Removed extraneous text from target-parameter (leftover from sip-
4244bis). Changed the terminology from the "reason" to the
"mechanism" to avoid ambiguity with parameter.
4. Various changes to clarify some of the text around privacy.
5. Reverted proxy response handling text to previous form - just
changing the privacy aspects to anonymize, rather than remove.
6. Other editorial changes to condense and simplify.
7. Moved Privacy examples to Appendix.
8. Added forking to Basic call example.
Changes from barnes-sip-4244bis-00 to barnes-sipcore-4244bis-00: Changes from barnes-sip-4244bis-00 to barnes-sipcore-4244bis-00:
1. Added tags for each type of retargeting including proxy hops, 1. Added tags for each type of retargeting including proxy hops,
etc. - i.e., a tag is defined for each specific mechanism by etc. - i.e., a tag is defined for each specific mechanism by
which the new Request-URI is determined. Note, this is which the new Request-URI is determined. Note, this is
extremely helpful in terms of backwards compatibility. extremely helpful in terms of backwards compatibility.
2. Fixed all the examples. Made sure loose routing was used in all 2. Fixed all the examples. Made sure loose routing was used in all
of them. of them.
3. Removed example where a proxy using strict routing is using 3. Removed example where a proxy using strict routing is using
History-Info for avoiding trying same route twice. History-Info for avoiding trying same route twice.
4. Remove redundant Redirect Server example. 4. Remove redundant Redirect Server example.
5. Index are now mandated to start at "1" instead of recommended. 5. Index is now mandated to start at "1" instead of recommended.
6. Clarified 3xx behavior as the entity sending the 3XX response 6. Updated 3xx behavior as the entity sending the 3XX response MUST
MUST add the hi-target attribute to the previous hi-entry to add the hi-target attribute to the previous hi-entry to ensure
ensure that it is appropriately tagged (i.e., it's the only one that it is appropriately tagged (i.e., it's the only one that
that knows how the contact in the 3xx was determined.) knows how the contact in the 3xx was determined.)
7. Removed lots of ambiguity by making many "MAYs" into "SHOULDs" 7. Removed lots of ambiguity by making many "MAYs" into "SHOULDs"
and "some "SHOULDs" into "MUSTs". and some "SHOULDs" into "MUSTs".
8. Privacy is now recommended to be done by anonymizing entries as 8. Privacy is now recommended to be done by anonymizing entries as
per RFC 3323 instead of by removing or omitting hi-entry(s). per RFC 3323 instead of by removing or omitting hi-entry(s).
9. Requirement for TLS is now same level as per RFC 3261. 9. Requirement for TLS is now same level as per RFC 3261.
10. Clarified behavior for "Privacy" (i.e., that Privacy is for Hi- 10. Clarified behavior for "Privacy" (i.e., that Privacy is for Hi-
entries, not headers). entries, not headers).
11. Removed "OPTIONALITY" as specific requirements, since it's 11. Removed "OPTIONALITY" as specific requirements, since it's
skipping to change at page 29, line 43 skipping to change at page 32, line 8
4. Added hi-target parameter values to HI header to ABNF and 4. Added hi-target parameter values to HI header to ABNF and
protocol description, as well as defining proxy, UAC and UAS protocol description, as well as defining proxy, UAC and UAS
behavior for the parameter. behavior for the parameter.
5. Simplified example call flow in section 4.5. Moved previous call 5. Simplified example call flow in section 4.5. Moved previous call
flow to appendix. flow to appendix.
6. Fixed ABNF per RFC4244 errata "dot" -> "." and added new 6. Fixed ABNF per RFC4244 errata "dot" -> "." and added new
parameter. parameter.
13. References 14. References
13.1. Normative References 14.1. Normative References
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E. A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261, Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002. June 2002.
[RFC3326] Schulzrinne, H., Oran, D., and G. Camarillo, "The Reason [RFC3326] Schulzrinne, H., Oran, D., and G. Camarillo, "The Reason
Header Field for the Session Initiation Protocol (SIP)", Header Field for the Session Initiation Protocol (SIP)",
RFC 3326, December 2002. RFC 3326, December 2002.
skipping to change at page 30, line 22 skipping to change at page 32, line 34
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008. (TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC4244] Barnes, M., "An Extension to the Session Initiation [RFC4244] Barnes, M., "An Extension to the Session Initiation
Protocol (SIP) for Request History Information", RFC 4244, Protocol (SIP) for Request History Information", RFC 4244,
November 2005. November 2005.
13.2. Informative References 14.2. Informative References
[RFC5627] Rosenberg, J., "Obtaining and Using Globally Routable User [RFC5627] Rosenberg, J., "Obtaining and Using Globally Routable User
Agent URIs (GRUUs) in the Session Initiation Protocol Agent URIs (GRUUs) in the Session Initiation Protocol
(SIP)", RFC 5627, October 2009. (SIP)", RFC 5627, October 2009.
[RFC5630] Audet, F., "The Use of the SIPS URI Scheme in the Session [RFC5630] Audet, F., "The Use of the SIPS URI Scheme in the Session
Initiation Protocol (SIP)", RFC 5630, October 2009. Initiation Protocol (SIP)", RFC 5630, October 2009.
[RFC3087] Campbell, B. and R. Sparks, "Control of Service Context [RFC3087] Campbell, B. and R. Sparks, "Control of Service Context
using SIP Request-URI", RFC 3087, April 2001. using SIP Request-URI", RFC 3087, April 2001.
[RFC4240] Burger, E., Van Dyke, J., and A. Spitzer, "Basic Network [RFC4240] Burger, E., Van Dyke, J., and A. Spitzer, "Basic Network
Media Services with SIP", RFC 4240, December 2005. Media Services with SIP", RFC 4240, December 2005.
[RFC3969] Camarillo, G., "The Internet Assigned Number Authority [RFC3969] Camarillo, G., "The Internet Assigned Number Authority
(IANA) Uniform Resource Identifier (URI) Parameter (IANA) Uniform Resource Identifier (URI) Parameter
Registry for the Session Initiation Protocol (SIP)", Registry for the Session Initiation Protocol (SIP)",
BCP 99, RFC 3969, December 2004. BCP 99, RFC 3969, December 2004.
[RFC3966] Schulzrinne, H., "The tel URI for Telephone Numbers",
RFC 3966, December 2004.
Appendix A. Request History Requirements Appendix A. Request History Requirements
The following list constitutes a set of requirements for a "Request The following list constitutes a set of requirements for a "Request
History" capability. History" capability.
1. CAPABILITY-req: The "Request History" capability provides a 1. CAPABILITY-req: The "Request History" capability provides a
capability to inform proxies and UAs involved in processing a capability to inform proxies and UAs involved in processing a
request about the history/progress of that request. Although request about the history/progress of that request. Although
this is inherently provided when the retarget is in response to a this is inherently provided when the retarget is in response to a
SIP redirect, it is deemed useful for non-redirect retargeting SIP redirect, it is deemed useful for non-redirect retargeting
scenarios, as well. scenarios, as well.
2. GENERATION-req: "Request History" information is generated when 2. GENERATION-req: "Request History" information is generated when
the request is retargeted. the request is retargeted.
A. In some scenarios, it might be possible for more than one A. In some scenarios, it might be possible for more than one
instance of retargeting to occur within the same Proxy. A instance of retargeting to occur within the same Proxy. A
proxy should also generate Request History information for proxy MUST also generate Request History information for the
the 'internal retargeting'. 'internal retargeting'.
B. An entity (UA or proxy) retargeting in response to a redirect B. An entity (UA or proxy) retargeting in response to a redirect
or REFER should include any Request History information from or REFER MUST include any Request History information from
the redirect/REFER in the new request. the redirect/REFER in the new request.
3. ISSUER-req: "Request History" information can be generated by a 3. ISSUER-req: "Request History" information can be generated by a
UA or proxy. It can be passed in both requests and responses. UA or proxy. It can be passed in both requests and responses.
4. CONTENT-req: The "Request History" information for each 4. CONTENT-req: The "Request History" information for each
occurrence of retargeting shall include the following: occurrence of retargeting shall include the following:
A. The new URI or address to which the request is in the process A. The new URI or address to which the request is in the process
of being retargeted, of being retargeted,
skipping to change at page 31, line 37 skipping to change at page 34, line 6
B. The URI or address from which the request was retargeted, and B. The URI or address from which the request was retargeted, and
wether the retarget URI was an AOR wether the retarget URI was an AOR
C. The mechanism by which the new URI or address was determined, C. The mechanism by which the new URI or address was determined,
D. The reason for the Request-URI or address modification, D. The reason for the Request-URI or address modification,
E. Chronological ordering of the Request History information. E. Chronological ordering of the Request History information.
5. REQUEST-VALIDITY-req: Request History is applicable to requests 5. REQUEST-VALIDITY-req: Request History is applicable to requests
not sent within an established dialog (e.g., INVITE, REGISTER, not sent within an early or established dialog (e.g., INVITE,
MESSAGE, and OPTIONS). REGISTER, MESSAGE, and OPTIONS).
6. BACKWARDS-req: Request History information may be passed from the 6. BACKWARDS-req: Request History information may be passed from the
generating entity backwards towards the UAC. This is needed to generating entity backwards towards the UAC. This is needed to
enable services that inform the calling party about the dialog enable services that inform the calling party about the dialog
establishment attempts. establishment attempts.
7. FORWARDS-req: Request History information may also be included by 7. FORWARDS-req: Request History information may also be included by
the generating entity in the request, if it is forwarded onwards. the generating entity in the request, if it is forwarded onwards.
A.1. Security Requirements A.1. Security Requirements
skipping to change at page 32, line 42 skipping to change at page 35, line 6
content has been altered. content has been altered.
2. SEC-req-2: The ordering of the Request History information must 2. SEC-req-2: The ordering of the Request History information must
be preserved at each instance of retargeting. be preserved at each instance of retargeting.
3. SEC-req-3: The entity receiving the information conveyed by the 3. SEC-req-3: The entity receiving the information conveyed by the
Request History must be able to authenticate the entity providing Request History must be able to authenticate the entity providing
the request. the request.
4. SEC-req-4: To ensure the confidentiality of the Request History 4. SEC-req-4: To ensure the confidentiality of the Request History
information, only entities that process the request should have information, only entities that process the request SHOULD have
visibility to the information. visibility to the information.
It should be noted that these security requirements apply to any It should be noted that these security requirements apply to any
entity making use of the Request History information. entity making use of the Request History information.
A.2. Privacy Requirements A.2. Privacy Requirements
Since the Request-URI that is captured could inadvertently reveal Since the Request-URI that is captured could inadvertently reveal
information about the originator, there are general privacy information about the originator, there are general privacy
requirements that MUST be met: requirements that MUST be met:
skipping to change at page 35, line 15 skipping to change at page 37, line 46
F1 INVITE alice -> example.com F1 INVITE alice -> example.com
INVITE sip:alice@example.com SIP/2.0 INVITE sip:alice@example.com SIP/2.0
Via: SIP/2.0/TCP 192.0.2.3:5060 Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com> From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com> To: Bob <sip:bob@example.com>
Supported: histinfo Supported: histinfo
Call-Id: 12345600@example.com Call-Id: 12345600@example.com
CSeq: 1 INVITE CSeq: 1 INVITE
History-Info: <sip:bob@example.com>;index=1
Contact: Alice <sip:alice@192.0.2.3> Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp Content-Type: application/sdp
Content-Length: <appropriate value> Content-Length: <appropriate value>
<!-- SDP Not Shown --> <!-- SDP Not Shown -->
F2 INVITE example.com -> Bob F2 INVITE example.com -> Bob
INVITE sip:bob@192.0.2.4 SIP/2.0 INVITE sip:bob@192.0.2.4 SIP/2.0
Via: SIP/2.0/TCP proxy.example.com:5060 Via: SIP/2.0/TCP proxy.example.com:5060
Via: SIP/2.0/TCP 192.0.2.3:5060 Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com> From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com> To: Bob <sip:bob@example.com>
Supported: histinfo Supported: histinfo
Call-Id: 12345600@example.com Call-Id: 12345600@example.com
CSeq: 1 INVITE CSeq: 1 INVITE
skipping to change at page 35, line 32 skipping to change at page 38, line 16
INVITE sip:bob@192.0.2.4 SIP/2.0 INVITE sip:bob@192.0.2.4 SIP/2.0
Via: SIP/2.0/TCP proxy.example.com:5060 Via: SIP/2.0/TCP proxy.example.com:5060
Via: SIP/2.0/TCP 192.0.2.3:5060 Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com> From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com> To: Bob <sip:bob@example.com>
Supported: histinfo Supported: histinfo
Call-Id: 12345600@example.com Call-Id: 12345600@example.com
CSeq: 1 INVITE CSeq: 1 INVITE
Record-Route: <sip:proxy.example.com;lr> Record-Route: <sip:proxy.example.com;lr>
History-Info: <sip:bob@example.com>;index=1 History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4>;index=1.1;rc History-Info: <sip:bob@192.0.2.4>;index=1.1;rc=1
Contact: Alice <sip:alice@192.0.2.3> Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp Content-Type: application/sdp
Content-Length: <appropriate value> Content-Length: <appropriate value>
<!-- SDP Not Shown --> <!-- SDP Not Shown -->
F3 100 Trying example.com -> alice F3 100 Trying example.com -> alice
SIP/2.0 100 Trying SIP/2.0 100 Trying
Via: SIP/2.0/TCP 192.0.2.3:5060 Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com> From: Alice <sip:alice@example.com>
skipping to change at page 36, line 15 skipping to change at page 38, line 43
SIP/2.0 302 Moved Temporarily SIP/2.0 302 Moved Temporarily
Via: SIP/2.0/TCP proxy.example.com:5060 Via: SIP/2.0/TCP proxy.example.com:5060
Via: SIP/2.0/TCP 192.0.2.3:5060 Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com> From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com>;tag=3 To: Bob <sip:bob@example.com>;tag=3
Call-Id: 12345600@example.com Call-Id: 12345600@example.com
CSeq: 1 INVITE CSeq: 1 INVITE
Record-Route: <sip:proxy.example.com;lr> Record-Route: <sip:proxy.example.com;lr>
History-Info: <sip:bob@example.com>;index=1 History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4>;index=1.1;rc History-Info: <sip:bob@192.0.2.4>;index=1.1;rc=1
Contact: <sip:office@example.com;hit=mp> Contact: <sip:office@example.com>;mp=1
Content-Length: 0 Content-Length: 0
F5 ACK 192.0.2.4 -> Bob F5 ACK 192.0.2.4 -> Bob
ACK sip:home@example.com SIP/2.0 ACK sip:home@example.com SIP/2.0
Via: SIP/2.0/TCP proxy.example.com:5060 Via: SIP/2.0/TCP proxy.example.com:5060
From: Alice <sip:alice@example.com> From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com> To: Bob <sip:bob@example.com>
Call-Id: 12345600@example.com Call-Id: 12345600@example.com
CSeq: 1 ACK CSeq: 1 ACK
Content-Length: 0 Content-Length: 0
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INVITE sip:office@192.0.2.3.com SIP/2.0 INVITE sip:office@192.0.2.3.com SIP/2.0
Via: SIP/2.0/TCP proxy.example.com:5060;branch=2 Via: SIP/2.0/TCP proxy.example.com:5060;branch=2
Via: SIP/2.0/TCP 192.0.2.3:5060 Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com> From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com> To: Bob <sip:bob@example.com>
Supported: histinfo Supported: histinfo
Call-Id: 12345600@example.com Call-Id: 12345600@example.com
Record-Route: <sip:proxy.example.com;lr> Record-Route: <sip:proxy.example.com;lr>
History-Info: <sip:bob@example.com>;index=1 History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4?Reason=SIP;cause=302>;\ History-Info: <sip:bob@192.0.2.4?Reason=SIP;cause=302>;\
index=1.1;rc index=1.1;rc=1
History-Info: <sip:office@example.com>;index=1.2;mp=1 History-Info: <sip:office@example.com>;index=1.2;mp=1
History-Info: <sip:office@192.0.2.5>;index=1.2.1 History-Info: <sip:office@192.0.2.5>;index=1.2.1
CSeq: 1 INVITE CSeq: 1 INVITE
Contact: Alice <sip:alice@192.0.2.3> Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp Content-Type: application/sdp
Content-Length: <appropriate value> Content-Length: <appropriate value>
<!-- SDP Not Shown --> <!-- SDP Not Shown -->
F7 180 Ringing office -> example.com F7 180 Ringing office -> example.com
SIP/2.0 180 Ringing SIP/2.0 180 Ringing
Via: SIP/2.0/TCP proxy.example.com:5060;branch=2 Via: SIP/2.0/TCP proxy.example.com:5060;branch=2
Via: SIP/2.0/TCP 192.0.2.3:5060 Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com> From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com>;tag=5 To: Bob <sip:bob@example.com>;tag=5
Supported: histinfo Supported: histinfo
Call-ID: 12345600@example.com Call-ID: 12345600@example.com
Record-Route: <sip:proxy.example.com;lr> Record-Route: <sip:proxy.example.com;lr>
skipping to change at page 37, line 18 skipping to change at page 40, line 16
SIP/2.0 180 Ringing SIP/2.0 180 Ringing
Via: SIP/2.0/TCP proxy.example.com:5060;branch=2 Via: SIP/2.0/TCP proxy.example.com:5060;branch=2
Via: SIP/2.0/TCP 192.0.2.3:5060 Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com> From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com>;tag=5 To: Bob <sip:bob@example.com>;tag=5
Supported: histinfo Supported: histinfo
Call-ID: 12345600@example.com Call-ID: 12345600@example.com
Record-Route: <sip:proxy.example.com;lr> Record-Route: <sip:proxy.example.com;lr>
History-Info: <sip:bob@example.com>;index=1 History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4?Reason=SIP;cause=302>;\ History-Info: <sip:bob@192.0.2.4?Reason=SIP;cause=302>;\
index=1.1;rc index=1.1;rc=1
History-Info: <sip:office@example.com>;index=1.2;mp=1 History-Info: <sip:office@example.com>;index=1.2;mp=1
History-Info: <sip:office@192.0.2.5>;index=1.2.1 History-Info: <sip:office@192.0.2.5>;index=1.2.1
CSeq: 1 INVITE CSeq: 1 INVITE
Content-Length: 0 Content-Length: 0
F8 180 Ringing example.com -> alice F8 180 Ringing example.com -> alice
SIP/2.0 180 Ringing SIP/2.0 180 Ringing
Via: SIP/2.0/TCP example.com:5060 Via: SIP/2.0/TCP example.com:5060
From: Alice <sip:alice@example.com> From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com> To: Bob <sip:bob@example.com>
Supported: histinfo Supported: histinfo
Call-Id: 12345600@example.com Call-Id: 12345600@example.com
History-Info: <sip:bob@example.com>;index=1 History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4?Reason=SIP;cause=302>;\ History-Info: <sip:bob@192.0.2.4?Reason=SIP;cause=302>;\
index=1.1;rc index=1.1;rc=1
History-Info: <sip:office@example.com>;index=1.2;mp=1 History-Info: <sip:office@example.com>;index=1.2;mp=1
History-Info: <sip:office@192.0.2.5>;index=1.2.1 History-Info: <sip:office@192.0.2.5>;index=1.2.1
CSeq: 1 INVITE CSeq: 1 INVITE
Content-Length: 0 Content-Length: 0
F9 INVITE example.com -> home F9 INVITE example.com -> home
INVITE sip:home@192.0.2.6 SIP/2.0 INVITE sip:home@192.0.2.6 SIP/2.0
Via: SIP/2.0/TCP proxy.example.com:5060;branch=3 Via: SIP/2.0/TCP proxy.example.com:5060;branch=3
Via: SIP/2.0/TCP 192.0.2.3:5060 Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com> From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com> To: Bob <sip:bob@example.com>
Supported: histinfo Supported: histinfo
Call-Id: 12345600@example.com Call-Id: 12345600@example.com
Record-Route: <sip:proxy.example.com;lr> Record-Route: <sip:proxy.example.com;lr>
History-Info: <sip:bob@example.com>;index=1 History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4?Reason=SIP;cause=302>;\ History-Info: <sip:bob@192.0.2.4?Reason=SIP;cause=302>;\
index=1.1;rc index=1.1;rc=1
History-Info: <sip:office@example.com>;index=1.2;mp=1 History-Info: <sip:office@example.com>;index=1.2;mp=1
History-Info: <sip:office@192.0.2.5?Reason=SIP;cause=480>;\ History-Info: <sip:office@192.0.2.5?Reason=SIP;cause=480>;\
index=1.2.1>;index=1.2.1 index=1.2.1>;index=1.2.1
History-Info: <sip:home@example.com>;index=1.3;mp=1.2 History-Info: <sip:home@example.com>;index=1.3;mp=1
History-Info: <sip:home@192.0.2.6>;index=1.3.1 History-Info: <sip:home@192.0.2.6>;index=1.3.1
CSeq: 1 INVITE CSeq: 1 INVITE
Contact: Alice <sip:alice@192.0.2.3> Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp Content-Type: application/sdp
Content-Length: <appropriate value> Content-Length: <appropriate value>
<!-- SDP Not Shown --> <!-- SDP Not Shown -->
F10 100 Trying home -> example.com F10 100 Trying home -> example.com
SIP/2.0 100 Trying SIP/2.0 100 Trying
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SIP/2.0 486 Busy Here SIP/2.0 486 Busy Here
Via: SIP/2.0/TCP proxy.example.com:5060;branch=3 Via: SIP/2.0/TCP proxy.example.com:5060;branch=3
Via: SIP/2.0/TCP 192.0.2.3:5060 Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com> From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com> To: Bob <sip:bob@example.com>
Call-Id: 12345600@example.com Call-Id: 12345600@example.com
Record-Route: <sip:proxy.example.com;lr> Record-Route: <sip:proxy.example.com;lr>
History-Info: <sip:bob@example.com>;index=1 History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4?Reason=SIP;cause=302>;\ History-Info: <sip:bob@192.0.2.4?Reason=SIP;cause=302>;\
index=1.1;rc index=1.1;rc=1
History-Info: <sip:office@example.com>;index=1.2;mp=1 History-Info: <sip:office@example.com>;index=1.2;mp=1
History-Info: <sip:office@192.0.2.5?Reason=SIP;cause=480>;\ History-Info: <sip:office@192.0.2.5?Reason=SIP;cause=480>;\
index=1.2.1>;index=1.2.1 index=1.2.1>;index=1.2.1
History-Info: <sip:home@example.com>;index=1.3;mp=1.2 History-Info: <sip:home@example.com>;index=1.3;mp=1
History-Info: <sip:home@192.0.2.6>;index=1.3.1 History-Info: <sip:home@192.0.2.6>;index=1.3.1
CSeq: 1 INVITE CSeq: 1 INVITE
Content-Length: 0 Content-Length: 0
F12 486 Busy Here example.com -> alice F12 486 Busy Here example.com -> alice
SIP/2.0 486 Busy Here SIP/2.0 486 Busy Here
Via: SIP/2.0/TCP 192.0.2.3:5060 Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com> From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com> To: Bob <sip:bob@example.com>
Call-Id: 12345600@example.com Call-Id: 12345600@example.com
History-Info: <sip:bob@example.com>;index=1 History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4?Reason=SIP;cause=302>;\ History-Info: <sip:bob@192.0.2.4?Reason=SIP;cause=302>;\
index=1.1;rc index=1.1;rc=1
History-Info: <sip:office@example.com>;index=1.2;mp=1 History-Info: <sip:office@example.com>;index=1.2;mp=1
History-Info: <sip:office@192.0.2.5?Reason=SIP;cause=480>;\ History-Info: <sip:office@192.0.2.5?Reason=SIP;cause=480>;\
index=1.2.1>;index=1.2.1 index=1.2.1>;index=1.2.1
History-Info: <sip:home@example.com>;index=1.3;mp=1.2 History-Info: <sip:home@example.com>;index=1.3;mp=1
History-Info: <sip:home@192.0.2.6>;index=1.3.1 History-Info: <sip:home@192.0.2.6>;index=1.3.1
CSeq: 1 INVITE CSeq: 1 INVITE
Content-Length: 0 Content-Length: 0
F13 ACK example.com -> home F13 ACK example.com -> home
ACK sip:home@example.com SIP/2.0 ACK sip:home@example.com SIP/2.0
Via: SIP/2.0/TCP proxy.example.com:5060 Via: SIP/2.0/TCP proxy.example.com:5060
From: Alice <sip:alice@example.com> From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com> To: Bob <sip:bob@example.com>
Call-Id: 12345600@example.com Call-Id: 12345600@example.com
skipping to change at page 40, line 27 skipping to change at page 43, line 27
Via: SIP/2.0/TCP 192.0.2.3:5060 Via: SIP/2.0/TCP 192.0.2.3:5060
From: Alice <sip:alice@example.com> From: Alice <sip:alice@example.com>
To: Bob <sip:bob@example.com> To: Bob <sip:bob@example.com>
Call-Id: 12345600@example.com Call-Id: 12345600@example.com
Route: <sip:proxy.example.com;lr> Route: <sip:proxy.example.com;lr>
CSeq: 1 ACK CSeq: 1 ACK
Content-Length: 0 Content-Length: 0
B.2. History-Info with Privacy Header B.2. History-Info with Privacy Header
This example provides a basic call scenario without forking, with This example provides a basic call scenario without forking. Alice
sip:biloxi.example.com adding the Privacy header indicating that the has indicated that she wants Privacy associated with her History-Info
History-Info header information is anonymized outside the entry and sip:biloxi.example.com adds Privacy headers indicating that
biloxi.example.com domain. the History-Info header information is anonymized outside the
biloxi.example.com domain. Note, that if the atlanta.example.com
proxy had added privacy headers to all its hi-entries, then all the
hi-entries in the response would be anonymous.
Alice atlanta.example.com biloxi.example.com Bob Alice atlanta.example.com biloxi.example.com Bob
| | | | | | | |
| INVITE sip:bob@biloxi.example.com;p=x | | INVITE sip:bob@biloxi.example.com;p=x |
|--------------->| | | |--------------->| | |
| Supported: histinfo | | | Supported: histinfo | |
| | | | | Privacy: History | |
| | INVITE sip:bob@biloxi.example.com;p=x | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| |--------------->| | | | | |
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1 | | INVITE sip:bob@biloxi.example.com;p=x
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1 | |--------------->| |
| | | | | History-Info: <sip:anonymous@anonymous.invalid>;index=1
| | | INVITE sip:bob@192.0.2.3 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| | |--------------->| | | | |
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1 | | | INVITE sip:bob@192.0.2.3
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1 | | |--------------->|
| History-Info: <sip:bob@192.0.2.3>;index=1.1.1;rc | History-Info: <sip:anonymous@anonymous.invalid>;index=1
| | | | | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| | | 200 | | History-Info: <sip:bob@192.0.2.3?Privacy=history>;index=1.1.1;rc=1.1
| | |<---------------| | | | |
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1 | | | 200 |
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1 | | |<---------------|
| History-Info: <sip:bob@192.0.2.3>;index=1.1.1;rc | History-Info: <sip:anonymous@anonymous.invalid>;index=1
| | | | | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| | 200 | | | History-Info: <sip:bob@192.0.2.3?Privacy=history>;index=1.1.1;rc=1.1
| |<---------------| | | | | |
| History-Info: <sip:anonymous@anonymous.invalid>;index=1 | | 200 | |
| History-Info: <sip:anonymous@anonymous.invalid>;index=1.1 | |<---------------| |
| History-Info: <sip:anonymous@anonymous.invalid>;index=1.1.1;rc | History-Info: <sip:anonymous@anonymous.invalid>;index=1
| | | | | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| 200 | | | | History-Info: <sip:anonymous@anonymous.invalid>;index=1.1.1;rc=1.1
|<---------------| | | | | | |
| History-Info: <sip:anonymous@anonymous.invalid>;index=1 | 200 | | |
| History-Info: <sip:anonymous@anonymous.invalid>;index=1.1 |<---------------| | |
| History-Info: <sip:anonymous@anonymous.invalid>;index=1.1.1;rc | History-Info: <sip:anonymous@anonymous.invalid>;index=1
| | | | | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| ACK | | | | History-Info: <sip:anonymous@anonymous.invalid>;index=1.1.1;rc=1.1
|--------------->| ACK | | | | | |
| |--------------->| ACK | | ACK | | |
| | |--------------->| |--------------->| ACK | |
| |--------------->| ACK |
| | |--------------->|
Figure 2: Example with Privacy Header Figure 2: Example with Privacy Header
B.3. Privacy Header for a Specific History-Info Entry B.3. Privacy Header for a Specific History-Info Entry
This example provides a basic call scenario similar to Appendix B.2, This example provides a basic call scenario similar to Appendix B.2,
however, due to local policy at sip:biloxi.example.com, only the however, due to local policy at sip:biloxi.example.com, only the
final hi-entry in the History-Info, which is Bob's local URI, final hi-entry in the History-Info, which is Bob's local URI,
contains a priv-value of "history", thus providing Alice with some contains a priv-value of "history", thus providing Alice with some
information about the history of the request, but anonymizing Bob's information about the history of the request, but anonymizing Bob's
local URI. local URI.
Alice atlanta.example.com biloxi.example.com Bob Alice atlanta.example.com biloxi.example.com Bob
| | | | | | | |
| INVITE sip:bob@biloxi.example.com;p=x | | INVITE sip:bob@biloxi.example.com;p=x |
|--------------->| | | |--------------->| | |
| Supported: histinfo | | | Supported: histinfo | |
| | | | | | | |
| | INVITE sip:bob@biloxi.example.com;p=x | | INVITE sip:bob@biloxi.example.com;p=x
| |--------------->| | | |--------------->| |
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| | | | | | | |
| | | INVITE sip:bob@192.0.2.3 | | | INVITE sip:bob@192.0.2.3
| | |--------------->| | | |--------------->|
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| History-Info: <sip:bob@192.0.2.3?Privacy=history>;index=1.1.1;rc | History-Info: <sip:bob@192.0.2.3>;index=1.1.1;rc=1.1
| | | | | | | |
| | | 200 | | | | 200 |
| | |<---------------| | | |<---------------|
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| History-Info: <sip:bob@192.0.2.3?Privacy=history>;index=1.1.1;rc | History-Info: <sip:bob@192.0.2.3?Privacy=history>;index=1.1.1;rc=1.1
| | | | | | | |
| | 200 | | | | 200 | |
| |<---------------| | | |<---------------| |
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| History-Info: <sip:anonymous@anynymous.invalid>;index=1.1.1;rc | History-Info: <sip:anonymous@anonymous.invalid>;index=1.1.1;rc=1.1
| | | | | | | |
| 200 | | | | 200 | | |
|<---------------| | | |<---------------| | |
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
| History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1 | History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1
| History-Info: <sip:anonymous@anynymous.invalid>;index=1.1.1;rc | History-Info: <sip:anonymous@anynymous.invalid>;index=1.1.1;rc=1.1
| | | | | | | |
| ACK | | | | ACK | | |
|--------------->| ACK | | |--------------->| ACK | |
| |--------------->| ACK | | |--------------->| ACK |
| | |--------------->| | | |--------------->|
Figure 3: Example with Privacy Header for Specific URI Figure 3: Example with Privacy Header for Specific URI
Authors' Addresses Authors' Addresses
Mary Barnes Mary Barnes
Polycom Polycom
TX TX
US US
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