draft-ietf-sipcore-rfc4244bis-08.txt   draft-ietf-sipcore-rfc4244bis-09.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: October 3, 2012 S. Schubert Expires: March 5, 2013 S. Schubert
NTT NTT
J. van Elburg J. van Elburg
Detecon International Gmbh Detecon International Gmbh
C. Holmberg C. Holmberg
Ericsson Ericsson
Apr 2012 Sept 2012
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-08.txt draft-ietf-sipcore-rfc4244bis-09.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 SIP request arrives at a specific the information as to how and why a SIP request arrives at a specific
application or user. This document defines an optional SIP header application or user. This document defines an optional SIP header
field, History-Info, for capturing the history information in field, History-Info, for capturing the history information in
requests. The document also defines SIP header field parameters for requests. The document also defines SIP header field parameters for
the History-Info and Contact header fields to tag the method by which the History-Info and Contact header fields to tag the method by which
the target of a request is determined. In addition, this the target of a request is determined. In addition, this
specification defines a value for the Privacy header field that specification defines a value for the Privacy header field that
directs the anonymization of values in the History-Info header field directs the anonymization of values in the History-Info header field.
This document obsoletes RFC 4244. This document obsoletes RFC 4244.
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.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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 October 3, 2012. This Internet-Draft will expire on March 5, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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modifications of such material outside the IETF Standards Process. modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling Without obtaining an adequate license from the person(s) controlling
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than English. than English.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 5 2. Conventions and Terminology . . . . . . . . . . . . . . . . . 4
3. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. History-Info Header Field Protocol Structure . . . . . . . . . 8 5. History-Info Header Field Protocol Structure . . . . . . . . . 7
5.1. History-Info Header Field Example Scenario . . . . . . . . 11 5.1. History-Info Header Field Example Scenario . . . . . . . . 10
6. User Agent Handling of the History-Info Header Field . . . . . 14 6. User Agent Handling of the History-Info Header Field . . . . . 13
6.1. User Agent Client (UAC) Behavior . . . . . . . . . . . . . 14 6.1. User Agent Client (UAC) Behavior . . . . . . . . . . . . . 13
6.2. User Agent Server (UAS) Behavior . . . . . . . . . . . . . 14 6.2. User Agent Server (UAS) Behavior . . . . . . . . . . . . . 13
7. Proxy/Intermediary Handling of History-Info Header Fields . . 14 7. Proxy/Intermediary Handling of History-Info Header Fields . . 13
8. Redirect Server Handling of History-Info Header Fields . . . . 15 8. Redirect Server Handling of History-Info Header Fields . . . . 14
9. Handling of History-Info Header Fields in Requests and 9. Handling of History-Info Header Fields in Requests and
Responses . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Responses . . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.1. Receiving a Request . . . . . . . . . . . . . . . . . . . 16 9.1. Receiving a Request . . . . . . . . . . . . . . . . . . . 15
9.2. Sending a Request with History-Info . . . . . . . . . . . 16 9.2. Sending a Request with History-Info . . . . . . . . . . . 15
9.3. Receiving a Response with History-Info or Request 9.3. Receiving a Response with History-Info or Request
Timeouts . . . . . . . . . . . . . . . . . . . . . . . . . 17 Timeouts . . . . . . . . . . . . . . . . . . . . . . . . . 16
9.4. Sending History-Info in Responses . . . . . . . . . . . . 17 9.4. Sending History-Info in Responses . . . . . . . . . . . . 16
10. Processing the History-Info Header Field . . . . . . . . . . . 18 10. Processing the History-Info Header Field . . . . . . . . . . . 17
10.1. Privacy in the History-Info Header Field . . . . . . . . . 18 10.1. Privacy in the History-Info Header Field . . . . . . . . . 17
10.1.1. Indicating Privacy . . . . . . . . . . . . . . . . . 18 10.1.1. Indicating Privacy . . . . . . . . . . . . . . . . . 17
10.1.2. Applying Privacy . . . . . . . . . . . . . . . . . . 19 10.1.2. Applying Privacy . . . . . . . . . . . . . . . . . . 18
10.2. Reason in the History-Info Header Field . . . . . . . . . 20 10.2. Reason in the History-Info Header Field . . . . . . . . . 19
10.3. Indexing in the History-Info Header Field . . . . . . . . 20 10.3. Indexing in the History-Info Header Field . . . . . . . . 20
10.4. Mechanism for Target Determination in the History-Info 10.4. Mechanism for Target Determination in the History-Info
Header Field . . . . . . . . . . . . . . . . . . . . . . . 22 Header Field . . . . . . . . . . . . . . . . . . . . . . . 21
11. Application Considerations . . . . . . . . . . . . . . . . . . 23 11. Application Considerations . . . . . . . . . . . . . . . . . . 22
12. Application Specific Usage . . . . . . . . . . . . . . . . . . 25 12. Application Specific Usage . . . . . . . . . . . . . . . . . . 24
12.1. PBX Voicemail . . . . . . . . . . . . . . . . . . . . . . 25 12.1. PBX Voicemail . . . . . . . . . . . . . . . . . . . . . . 24
12.2. Consumer Voicemail . . . . . . . . . . . . . . . . . . . . 26 12.2. Consumer Voicemail . . . . . . . . . . . . . . . . . . . . 25
13. Security Considerations . . . . . . . . . . . . . . . . . . . 26 13. Security Considerations . . . . . . . . . . . . . . . . . . . 25
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27 14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
14.1. Registration of New SIP History-Info Header Field . . . . 27 14.1. Registration of New SIP History-Info Header Field . . . . 26
14.2. Registration of "history" for SIP Privacy Header Field . . 27 14.2. Registration of "history" for SIP Privacy Header Field . . 27
14.3. Registration of Header Field Parameters . . . . . . . . . 28 14.3. Registration of Header Field Parameters . . . . . . . . . 27
15. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 28 15. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 27
16. Changes from RFC 4244 . . . . . . . . . . . . . . . . . . . . 29 16. Changes from RFC 4244 . . . . . . . . . . . . . . . . . . . . 28
16.1. Backwards compatibility . . . . . . . . . . . . . . . . . 30 16.1. Backwards compatibility . . . . . . . . . . . . . . . . . 30
17. Changes since last Version . . . . . . . . . . . . . . . . . . 31 17. References . . . . . . . . . . . . . . . . . . . . . . . . . . 31
18. References . . . . . . . . . . . . . . . . . . . . . . . . . . 38 17.1. Normative References . . . . . . . . . . . . . . . . . . . 31
18.1. Normative References . . . . . . . . . . . . . . . . . . . 38 17.2. Informative References . . . . . . . . . . . . . . . . . . 32
18.2. Informative References . . . . . . . . . . . . . . . . . . 39 Appendix A. Request History Requirements . . . . . . . . . . . . 32
Appendix A. Request History Requirements . . . . . . . . . . . . 39 A.1. Security Requirements . . . . . . . . . . . . . . . . . . 33
A.1. Security Requirements . . . . . . . . . . . . . . . . . . 40 A.2. Privacy Requirements . . . . . . . . . . . . . . . . . . . 34
A.2. Privacy Requirements . . . . . . . . . . . . . . . . . . . 41 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 35
Appendix B. Example call flows . . . . . . . . . . . . . . . . . 42
B.1. PBX Voicemail call flow . . . . . . . . . . . . . . . . . 42
B.2. Consumer Voicemail example call flow . . . . . . . . . . . 46
B.3. Sequentially Forking (History-Info in Response) . . . . . 50
B.4. History-Info with Privacy Header Field . . . . . . . . . . 58
B.5. Privacy for a Specific History-Info Entry . . . . . . . . 62
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 66
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 a SIP request arrived at a specific to determine why and how a SIP request arrived at a specific
application. Examples of such services include (but are not limited application. Examples of such services include (but are not limited
to) sessions initiated to call centers via "click to talk" SIP to) sessions initiated to call centers via "click to talk" SIP
Uniform Resource Locators (URLs) on a web page, "call history/ Uniform Resource Locators (URLs) on a web page, "call history/
logging" style services within intelligent "call management" software logging" style services within intelligent "call management" software
for SIP User Agents (UAs), and calls to voicemail servers. Although for SIP User Agents (UAs), and calls to voicemail servers. Although
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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. SIP enable a wide variety of services for networks and end-users. SIP
header field parameters are defined for the History-Info and Contact header field parameters are defined for the History-Info and Contact
header fields to tag the method by which the target of a request is header fields to tag the method by which the target of a request is
determined. In addition, this specification defines a value for the determined. In addition, this specification defines a value for the
Privacy header field specific to the History-Info header. Privacy header field specific to the History-Info header.
The History-Info header field provides a building block for The History-Info header field provides a building block for
development of SIP based applications and services. The requirements development of SIP based applications and services. The requirements
for the solution described in this specification are included in for the solution described in this specification are included in
Appendix A. Example scenarios using the History-Info header field Appendix A.
are included in 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 specification to refer to the The term "retarget" is used in this specification to refer to the
process of a SIP entity changing the request-URI [RFC3261, section process of a SIP entity changing the request-URI [RFC3261, section
7.1] in a request based on the rules for determining request targets 7.1] in a request based on the rules for determining request targets
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these requests. these requests.
The following provides details for the information that is captured The following provides details for the information that is captured
in the History-Info header field entries for each target used for in the History-Info header field entries for each target used for
forwarding a request: forwarding a request:
o hi-targeted-to-uri: A mandatory parameter for capturing the o hi-targeted-to-uri: A mandatory parameter for capturing the
Request-URI for the specific request as it is forwarded. Request-URI for the specific request as it is forwarded.
o hi-index: A mandatory parameter for History-Info reflecting the o hi-index: A mandatory parameter for History-Info reflecting the
chronological order of the information, indexed to also reflect chronological order of the information, indexed to reflect the
the forking and nesting of requests. The format for this forking and retargeting of requests. The format for this
parameter is a sequance of nonnegative integers, separated by dots parameter is a sequance of nonnegative integers, separated by dots
to indicate the number of forward hops and retargets. This to indicate the number of forward hops and retargets. This
results in a tree representation of the history of the request, results in a tree representation of the history of the request,
with the lowest-level index reflecting a leaf. By adding the new with the lowest-level index reflecting a leaf. By adding the new
entries in order (i.e., following existing entries per the details entries in order (i.e., following existing entries per the details
in Section 10.3), including the index and sending the messages in Section 10.3), including the index and sending the messages
using a secure transport, the ordering of the History-Info header using a secure transport, the ordering of the History-Info header
fields in the request is assured. In addition, applications may fields in the request is assured. In addition, applications may
extract a variety of metrics (total number of retargets, total 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
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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 = addr-spec / name-addr hi-targeted-to-uri = addr-spec / name-addr
hi-param = hi-index / hi-target-param / hi-extension hi-param = hi-index / hi-target-param / hi-extension
hi-index = "index" EQUAL index-val hi-index = "index" EQUAL index-val
index-val = number *("." number)
index-val = number *("." number)
number = [ %31-39 *DIGIT ] DIGIT number = [ %31-39 *DIGIT ] DIGIT
hi-target-param = rc-param / mp-param / np-param hi-target-param = rc-param / mp-param / np-param
rc-param = "rc" EQUAL index-val rc-param = "rc" EQUAL index-val
mp-param = "mp" EQUAL index-val mp-param = "mp" EQUAL index-val
np-param = "np" EQUAL index-val np-param = "np" EQUAL index-val
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header field included in the hi-targeted-to-uri means that a header field included in the hi-targeted-to-uri means that a
specific hi-entry MUST be anonymized. specific hi-entry MUST be anonymized.
Note that since both the Reason and Privacy parameters are included Note that since both the Reason and Privacy parameters are included
in the hi-targeted-to-uri, these fields will not be available in the in 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]. case that the hi-targeted-to-uri is a Tel-URI [RFC3966].
The following provides examples of the format for the History-Info The following provides examples of the format for the History-Info
header field. Note that the backslash, CRLF and whitespace between header field. Note that the backslash, CRLF and whitespace between
the lines in the examples below are inserted for readability purposes the lines in the examples below are inserted for readability purposes
only. (But History-Info can be broken into multiple lines due to the only. Note, however, that History-Info can be broken into multiple
SWS that is part of HCOLON, COMMA and SEMI, and there can be multiple lines due to the SWS that is part of HCOLON, COMMA and SEMI, and
History-Info header fields due to the rule of section 7.3 [RFC3261].) there can be multiple History-Info header fields due to the rule of
section 7.3 [RFC3261]. Additional detailed examples are available in
[I-D.barnes-sipcore-rfc4244bis-callflows].
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=1.2 <sip:45432@192.168.0.3>;index=1.3;rc=1.2
5.1. History-Info Header Field Example Scenario 5.1. History-Info Header Field Example Scenario
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initial request-URI, including any parameters in the request URI. initial request-URI, including any parameters in the request URI.
Bob can recover that information by locating the last hi-entry with Bob can recover that information by locating the last hi-entry with
an "rc" header field parameter. This "rc" header field parameter an "rc" header field parameter. This "rc" header field parameter
contains the index of the hi-entry containing the lost target contains the index of the hi-entry containing the lost target
information - i.e., the sip:bob@biloxi.example.com hi-entry with information - i.e., the sip:bob@biloxi.example.com hi-entry with
index=1.1. Note that in the 200 response to Alice, an hi-entry is index=1.1. Note that in the 200 response to Alice, an hi-entry is
not included for the fork to sip:bob@192.0.2.7 (index 1.1.1) since not included for the fork to sip:bob@192.0.2.7 (index 1.1.1) since
biloxi.example.com had not received a response from that fork at the biloxi.example.com had not received a response from that fork at the
time it sent the 200 OK that ultimately reached Alice. time it sent the 200 OK that ultimately reached Alice.
Additional detailed scenarios are available in 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 |
| |--------------->| | | | |--------------->| | |
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follow the procedures in Section 9.3. follow the procedures in Section 9.3.
If the UAC generates further forks of the initial request (either due If the UAC generates further forks of the initial request (either due
to acting on a 3xx response or internally-directed forking to to acting on a 3xx response or internally-directed forking to
multiple destinations), the successive requests will add hi-entries multiple destinations), the successive requests will add hi-entries
with hi-indexes of 2, 3, etc. with hi-indexes of 2, 3, etc.
6.2. User Agent Server (UAS) Behavior 6.2. User Agent Server (UAS) Behavior
When receiving a request, a UAS MUST follow the procedures defined in When receiving a request, a UAS MUST follow the procedures defined in
Section 9.1. When sending a response other than a 3xx response, a Section 9.2. When sending a response other than a 3xx response, a
UAS MUST follows the procedures in Section 9.4. When sending a 3xx UAS MUST follows the procedures as defined in Section 9.4. When
response, the UAS MUST follow the procedures defined for a redirect sending a 3xx response, the UAS MUST follow the procedures defined
server per Section 8. An application at the UAS can make use of the for a redirect server per Section 8. An application at the UAS can
cached hi-entries as described in Section 11. make use of the cached hi-entries as described in Section 11.
7. Proxy/Intermediary Handling of History-Info Header Fields 7. Proxy/Intermediary Handling of History-Info Header Fields
This section describes the procedures for proxies and other SIP This section describes the procedures for proxies and other SIP
intermediaries for the handling of the History-Info header fields for intermediaries for the handling of the History-Info header fields for
each of the following scenarios: each of the following scenarios:
Receiving a Request: An intermediary MUST follow the procedures in Receiving a Request: An intermediary MUST follow the procedures in
Section 9.1 for the handling of hi-entries in incoming SIP Section 9.1 for the handling of hi-entries in incoming SIP
requests. requests.
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In some cases, an intermediary may retarget a request more than once In some cases, an intermediary may retarget a request more than once
before forwarding - i.e., a request is retargeted to a SIP entity before forwarding - i.e., a request is retargeted to a SIP entity
that is "internal" to the intermediary before the same intermediary that is "internal" to the intermediary before the same intermediary
retargets the request to an external target . A typical example retargets the request to an external target . A typical example
would be a proxy that retargets a request first to a different user would be a proxy that retargets a request first to a different user
(i.e., it maps to a different AOR) and then forwards to a registered (i.e., it maps to a different AOR) and then forwards to a registered
contact bound to the same AOR. In this case, the intermediary MUST contact bound to the same AOR. In this case, the intermediary MUST
add a hi-entry for (each of) the internal target(s) per the add a hi-entry for (each of) the internal target(s) per the
procedures in Section 9.2. The intermediary MAY include a Reason procedures in Section 9.2. The intermediary MAY include a Reason
header field in the hi-entry with the hi-targeted-to-uri that has header field in the hi-entry with the hi-targeted-to-uri that has
been retargeted as shown in the INVITE (F6) in the example in been retargeted.
Appendix B.3.
8. Redirect Server Handling of History-Info Header Fields 8. Redirect Server Handling of History-Info Header Fields
A redirect server MUST follow the procedures in Section 9.1 when it A redirect server MUST follow the procedures in Section 9.1 when it
receives a SIP Request. A redirect server MUST follow the procedures receives a SIP Request. A redirect server MUST follow the procedures
in Section 9.4 when it sends a SIP Response. When generating the in Section 9.4 when it sends a SIP Response. When generating the
Contact header field in a 3xx response, the redirect server MUST add Contact header field in a 3xx response, the redirect server MUST add
the appropriate "mp", "np" or "rc" header field parameter to each the appropriate "mp", "np" or "rc" header field parameter to each
Contact header field as described in Section 10.4, if applicable. Contact header field as described in Section 10.4, if applicable.
9. Handling of History-Info Header Fields in Requests and Responses 9. Handling of History-Info Header Fields in Requests and Responses
This section describes the procedures for SIP entities for the This section describes the procedures for SIP entities for the
handling of the History-Info header field in SIP requests and handling of the History-Info header field in SIP requests and
responses. responses.
9.1. Receiving a Request 9.1. Receiving a Request
When receiving a request, a SIP entity MUST create a cache containing When receiving a request, a SIP entity MUST keep a copy of the hi-
the hi-entries associated with the request. The hi-entries MUST be entries from the incoming request. This document describes this copy
added to the cache in the order in which they were received in the in terms of a cache containing the hi-entries associated with the
request. request. The hi-entries MUST be added to the cache in the order in
which they were received in the request.
If the Request-URI of the incoming request does not match the hi- If the Request-URI of the incoming request does not match the hi-
targeted-to-uri in the last hi-entry (i.e., the previous SIP entity targeted-to-uri in the last hi-entry (i.e., the previous SIP entity
that sent the request did not include a History-Info header field), that sent the request did not include a History-Info header field),
the SIP entity MUST add a hi-entry to end of the cache, on behalf of the SIP entity MUST add a hi-entry to end of the cache, on behalf of
the previous SIP entity, as follows: the previous SIP entity before proceeding to Section 9.2, as follows:
The SIP entity MUST set the hi-targeted-to-uri to the value of the The SIP entity MUST set the hi-targeted-to-uri to the value of the
Request-URI in the incoming request. If the Request-URI is a Tel- Request-URI in the incoming request. If the Request-URI is a Tel-
URI, it SHOULD be transformed into a SIP URI per section 19.1.6 of URI, it SHOULD be transformed into a SIP URI per section 19.1.6 of
[RFC3261] before being added as a hi-targted-to-uri. [RFC3261] before being added as a hi-targted-to-uri.
If privacy is required, the SIP entity MUST follow the procedures If privacy is required, the SIP entity MUST follow the procedures
of Section 10.1. of Section 10.1.
The SIP entity MUST set the hi-index parameter as described in The SIP entity MUST set the hi-index parameter as described in
Section 10.3. Section 10.3.
The SIP entity MUST NOT include an "rc", "mp" or "np" header field The SIP entity MUST NOT include an "rc", "mp" or "np" header field
parameter. parameter.
9.2. Sending a Request with History-Info 9.2. Sending a Request with History-Info
When sending a request, a SIP entity MUST include all cached hi- When sending a request, a SIP entity MUST include all the hi-entries
entries in the request. In addition, the SIP entity MUST add a new from the cache that was created per Section 9.1. In addition, the
hi-entry to the outgoing request, but the SIP entity MUST NOT add the SIP entity MUST add a new hi-entry to the outgoing request, but the
hi-entry to the cache at this time. The hi-entries in the outgoing SIP entity MUST NOT add the hi-entry to the cache at this time. The
request's History-Info header field is the preorder of the tree of hi-entries in the outgoing request's History-Info header field is the
hi-entries, that is, by the lexicographic ordering of the hi-indexes. preorder of the tree of hi-entries, that is, by the lexicographic
The new hi-entry is populated as follows: ordering of the hi-indexes. The new hi-entry is populated as
follows:
hi-targeted-to-uri: The hi-targeted-to-uri MUST be set to the value hi-targeted-to-uri: The hi-targeted-to-uri MUST be set to the value
of the Request-URI of the current (outgoing) request. of the Request-URI of the current (outgoing) request.
privacy: If privacy is required, the procedures of Section 10.1 MUST privacy: If privacy is required, the procedures of Section 10.1 MUST
be followed. be followed.
hi-index: The SIP entity MUST include an hi-index for the hi-entry hi-index: The SIP entity MUST include an hi-index for the hi-entry
as described in Section 10.3. as described in Section 10.3.
skipping to change at page 17, line 40 skipping to change at page 16, line 43
Step 3: Add additional hi-entries Step 3: Add additional hi-entries
The SIP entity MUST also add to the cache any hi-entries received The SIP entity MUST also add to the cache any hi-entries received
in the response that are not already in the cache. This situation in the response that are not already in the cache. This situation
can occur when the entity that generated the non-100 response can occur when the entity that generated the non-100 response
retargeted the request before generating the response. As per retargeted the request before generating the response. As per
Step 1, the hi-entries MUST be added to the cache in ascending Step 1, the hi-entries MUST be added to the cache in ascending
order as indicated by the values in the hi-index parameters of the order as indicated by the values in the hi-index parameters of the
hi-entries hi-entries
It is important to note that the cache does not contain hi-entries It is important to note that the cache (and the request or response)
for requests that have not yet received a non-100 response, so there does not contain hi-entries for requests that have not yet received a
can be gaps in indices (e.g., 1.2 and 1.4 could but present but not non-100 response, so there can be gaps in indices (e.g., 1.2 and 1.4
1.3). could but present but not 1.3).
9.4. Sending History-Info in Responses 9.4. Sending History-Info in Responses
When sending a response other than a 100, a SIP entity MUST include When sending a response other than a 100, a SIP entity MUST include
all the cached hi-entries in the response, subject to the privacy all the cached hi-entries in the response, subject to the privacy
consideration in Section 10.1.2, and with the following exception: If consideration in Section 10.1.2, and with the following exception: If
the received request contained no hi-entries and there is no the received request contained no hi-entries and there is no
"histinfo" option tag in the Supported header field, the SIP entity "histinfo" option tag in the Supported header field, the SIP entity
MUST NOT include History-Info in the response. MUST NOT include History-Info in the response.
skipping to change at page 22, line 18 skipping to change at page 21, line 27
above, with each new request having a unique index. Each index above, with each new request having a unique index. Each index
MUST be sequentially assigned. For example, if the index in the MUST be sequentially assigned. For example, if the index in the
last History-Info header field in the received request is 1.1, last History-Info header field in the received request is 1.1,
this processing entity would initialize its index to 1.1.1 for this processing 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 the first fork, 1.1.2 for the second, and so forth (see Figure 1
for an example). Note, that in the case of parallel forking, for an example). Note, that in the case of parallel forking,
only the hi-entry corresponding to the fork is included in the only the hi-entry corresponding to the fork is included in the
request because no response can yet have been received for any of request because no response can yet have been received for any of
the parallel forked requests. the parallel forked requests.
6. Missing entity: If the request clearly has a gap in the hi-entry, 6. Missing entity: If the request clearly has a gap in the hi-entry
the entity adding an hi-entry MUST add an index a nonnegative (i.e., the last hi-entry and Request-URI differ), the entity
integer of "0" to the current index prior to adding appropriate adding an hi-entry MUST add a single index with a value of "0"
index for the action to be taken. If the index of the last hi- (i.e., the non-negative integer zero) prior to adding the
entry in the request received was 1.1.2 and there was a missing appropriate index for the action to be taken. For example, if
hi-entry and the request was being forwarded to the next hop, the the index of the last hi-entry in the request received was 1.1.2
resulting index will be 1.1.2.0.1. and there was a missing hi-entry and the request was being
forwarded to the next hop, the resulting index will be 1.1.2.0.1.
10.4. Mechanism for Target Determination in the History-Info Header 10.4. Mechanism for Target Determination in the History-Info Header
Field Field
This specification defines two header field parameters, "rc", "mp" This specification defines three header field parameters, "rc", "mp"
and "np", indicating two mechanisms by which a new target for a and "np". The header field parameters "rc" and "mp" indicate the
request is determined. Both parameters contain an index whose value mechanism by which a new target for a request is determined. The
is the hi-index of the hi-entry with an hi-targeted-to-uri that header field "np" reflects that the target has not changed. All
represents the Request-URI that was retargeted. parameters contain an index whose value is the hi-index of the hi-
entry with an hi-targeted-to-uri that represents the Request-URI that
was retargeted.
The SIP entity MUST determine the specific parameter field to be The SIP entity MUST determine the specific parameter field to be
included in the hi-target-param, in the History-Info header field, as included in the hi-target-param, in the History-Info header field, as
the targets are added to the target set per the procedures in section the targets are added to the target set per the procedures in section
16.5 of [RFC3261] or per section 8.1.3.4 [RFC3261] in the case of 16.5 of [RFC3261] or per section 8.1.3.4 [RFC3261] in the case of
retargeting to a contact URI received in a 3xx response. In the retargeting to a contact URI received in a 3xx response. In the
latter case, the specific header field parameter in the Contact latter case, the specific header field parameter in the Contact
header field becomes the header field parameter that is used in the header field becomes the header field parameter that is used in the
hi-entry when the request is retargeted. If the Contact header field hi-entry when the request is retargeted. If the Contact header field
does not contain an "rc", "mp" or "np" header field parameter, then does not contain an "rc" or "mp" header field parameter, then the SIP
the SIP entity MUST NOT include an "rc", "mp" or "np" header field entity MUST NOT include an "rc" or "mp" header field parameter in the
parameter in the hi-target-param in the hi-entry when the request is hi-target-param in the hi-entry when the request is retargeted to a
retargeted to a contact URI received in a 3xx response.. contact URI received in a 3xx response. This is because the redirect
server is the only element with any knowledge on how the target was
determined. Note, that the "np" header field parameter is not
applicable in the case of redirection.
The SIP entity (intermediary or redirect server) determines the The SIP entity (intermediary or redirect server) determines the
specific header field parameter ("rc", "mp" or "np") to be used based specific header field parameter ("rc", "mp" or "np") to be used based
on the following criteria: on the following criteria:
o "rc": The Request-URI has changed while retaining the target user o "rc": The Request-URI has changed while retaining the target user
associated with the original Request-URI prior to retargeting. associated with the original Request-URI prior to retargeting.
o "mp": The target was determined based on a mapping to a user other o "mp": The target was determined based on a mapping to a user other
than the target user associated with the Request-URI being than the target user associated with the Request-URI being
retargeted. retargeted.
o "np": The target hasn't changed and associated Request-URI o "np": The target hasn't changed and the associated Request-URI
remained the same. remained the same.
Note that there are two scenarios by which the "mp" header field Note that there are two scenarios by which the "mp" header field
parameter can be derived. parameter can be derived.
o The mapping was done by the receiving entity on its own authority, 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 in which case the mp-value is the parent index of the hi-entry's
index. index.
o The mapping was done due to receiving a 3xx response, in which o The mapping was done due to receiving a 3xx response, in which
skipping to change at page 25, line 17 skipping to change at page 24, line 30
hi-entries prior to entries with hi-target value of "rc" header field hi-entries prior to entries with hi-target value of "rc" header field
parameter, to whom the call was targeted prior to its arrival at the parameter, to whom the call was targeted prior to its arrival at the
current agent. This could allow the agent the ability to decide how current agent. This could allow the agent the ability to decide how
they might forward or reroute the call if necessary (avoiding agents they might forward or reroute the call if necessary (avoiding agents
that were not previously available for whatever reason, etc.). that were not previously available for whatever reason, etc.).
Since support for History-Info header field is optional, a service Since support for History-Info header field is optional, a service
MUST define default behavior for requests and responses not MUST define default behavior for requests and responses not
containing History-Info header fields. For example, an entity may containing History-Info header fields. For example, an entity may
receive an incomplete set of hi-entries or hi-entries which are not receive an incomplete set of hi-entries or hi-entries which are not
tagged appropriately with an hi-target-param. This may not impact tagged appropriately with an hi-target-param in the case of entries
some applications (e.g., debug), however, it could require some added by entities that are only compliant to RFC4244. This may not
applications to make some default assumptions in this case. For impact some applications (e.g., debug), however, it could require
some 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.
12. Application Specific Usage 12. Application Specific Usage
Following are possible (non-normative) application-specific usages of Following are possible (non-normative) application-specific usages of
History-Info. History-Info.
skipping to change at page 25, line 44 skipping to change at page 25, line 11
information to determine the appropriate mailbox so an appropriate information to determine the appropriate mailbox so an appropriate
greeting can be provided and the appropriate party notified of the greeting can be provided and the appropriate party notified of the
message. message.
The original target is determined by finding the first hi-entry The original target is determined by finding the first hi-entry
tagged with "rc" and using the hi-entry referenced by the index of tagged with "rc" and using the hi-entry referenced by the index of
"rc" header field parameter as the target for determining the "rc" header field parameter as the target for determining the
appropriate mailbox. This hi-entry is used to populate the "target" appropriate mailbox. This hi-entry is used to populate the "target"
URI parameter as defined in [RFC4458] The VMS can look at the last URI parameter as defined in [RFC4458] The VMS can look at the last
hi-entry and find the target of the mailbox by looking at the URI hi-entry and find the target of the mailbox by looking at the URI
entry in the "target" URI parameter in the hi-entry. For example entry in the "target" URI parameter in the hi-entry.
call flow please refer to the Appendix B.1.
This example usage does not work properly in the presence of This example usage does not work properly in the presence of
forwarding that takes place before the call reaches the company in forwarding that takes place before the call reaches the company in
that case not the first hi-entry with an rc value, but the first hi- that case not the first hi-entry with an rc value, but the first hi-
entry with an rc value following an mp entry needs to be picked. entry with an rc value following an mp entry needs to be picked.
12.2. Consumer Voicemail 12.2. Consumer Voicemail
The voicemail system in these environment typically requires the last The voicemail system in these environment typically requires the last
called party information to determine the appropriate mailbox so an called party information to determine the appropriate mailbox so an
appropriate greeting can be provided and the appropriate party appropriate greeting can be provided and the appropriate party
notified of the message. notified of the message.
The last target is determined by finding the hi-entry referenced by The last target is determined by finding the hi-entry referenced by
the index of last hi-entry tagged with "rc" for determining the the index of last hi-entry tagged with "rc" for determining the
appropriate mailbox. This hi-entry is used to populate the "target" appropriate mailbox. This hi-entry is used to populate the "target"
URI parameter as defined in [RFC4458]. The VMS can look at the last URI parameter as defined in [RFC4458]. The VMS can look at the last
hi-entry and find the target of the mailbox by looking for the hi-entry and find the target of the mailbox by looking for the
"target" URI parameter in the hi-entry. For example call flow please "target" URI parameter in the hi-entry.
refer to the Appendix B.2.
13. Security Considerations 13. Security Considerations
The security requirements for this specification are specified in The security requirements for this specification are specified in
Appendix A.1. Appendix A.1.
This document defines a header field for SIP. The use of the This document defines a header field for SIP. The use of the
Transport Layer Security (TLS) protocol [RFC5246] as a mechanism to Transport Layer Security (TLS) protocol [RFC5246] as a mechanism to
ensure the overall confidentiality of the History-Info header fields ensure the overall confidentiality of the History-Info header fields
(SEC-req-4) is strongly RECOMMENDED. This results in History-Info (SEC-req-4) is strongly RECOMMENDED. This results in History-Info
skipping to change at page 30, line 13 skipping to change at page 29, line 23
specification and [RFC4244]: specification and [RFC4244]:
1. Added header field parameters to capture the specific method by 1. Added header field parameters to capture the specific method by
which a target is determined to facilitate processing by users of which a target is determined to facilitate processing by users of
the History-Info header field entries. A specific header field the History-Info header field entries. A specific header field
parameter is captured for each of the target URIs as the target parameter is captured for each of the target URIs as the target
set is determined (per section 16.5 of [RFC3261]). The header set is determined (per section 16.5 of [RFC3261]). The header
field parameter is used in both the History-Info and the Contact field parameter is used in both the History-Info and the Contact
header fields. header fields.
2. Rather than recommending that entries be removed in the case of 2. Added a way to indicate a gap in History-Info by adding a non-
negative integer of "0".
3. Rather than recommending that entries be removed in the case of
certain values of the Privacy header field, the entries are certain values of the Privacy header field, the entries are
anonymized. anonymized.
3. Updated the security section to be equivalent to the security 4. Updated the security section to be equivalent to the security
recommendations for other SIP header fields inserted by recommendations for other SIP header fields inserted by
intermediaries. intermediaries.
5. Removed Appendix B since a separate call flow document is being
published as a companion to this document.
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 field and eliminate the need to make the History-Info header field and eliminate the need to make
assumptions based upon the order of the entries and ensure that the assumptions based upon the order of the entries and ensure that the
most complete set of information is available to the applications. most complete 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 and removing the the text, moving the requirements to an appendix and removing the
inline references to the requirements. The examples were simplified inline references to the requirements. The examples were simplified
and updated to reflect the protocol changes. Several of the call and updated to reflect the protocol changes. Several of the call
flows in the appendix were removed and put into a separate document flows in the appendix were removed and put into a separate document
that includes additional use cases that require the new header field that includes additional use cases that require the new header field
parameters. parameters.
16.1. Backwards compatibility 16.1. 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 SIP header field parameter to the History-Info and Contact optional SIP header field parameter to the History-Info and Contact
header fields. Entities that have not implemented this specification header fields. Entities that have not implemented this specification
will ignore these parameters, however, per [RFC4244] an entity will will ignore these parameters, however, per [RFC4244] an entity will
not remove this parameter from an hi-entry. not remove these parameters from an hi-entry. While entities
compliant to this document and [RFC4244] must be able to recognize
gaps in the hi-entries, this document requires that an index of "0"
be used in this case. Whereas [RFC4244] recommended (but did not
require) the use of "1". However, since the ABNF in [RFC4244]
defines the index as a DIGIT, "0" would be a valid value, thus an
[RFC4244] implementation should not have an issue if it receives hi-
entries added by intermediaries compliant to this document.
As for the behavior of the entity followings have changed since the As for the behavior of the UACs, UASs and intermediaries, the
[RFC4244]. following additional normative changes have been made:
UAC behavior UAC behavior
1. Inclusion of option tag by UAC has changed from SHOULD to MUST. 1. Inclusion of option tag by UAC has changed from SHOULD to MUST.
2. Inclusion of hi-target-entry along with hi-index has changed from 2. Inclusion of hi-target-entry along with hi-index has changed from
MAY/RECOMMEND to MUST/MUST. MAY/RECOMMEND to MUST/MUST.
3. Behavior surrounding the addition of hi-target-entry based on 3xx 3. Behavior surrounding the addition of hi-target-entry based on 3xx
response has changed from MAY/SHOULD to MUST. response has changed from MAY/SHOULD to MUST.
None of the behavior changes would cause any backward compatibility None of the behavior changes would cause any backward or forward
issues. compatibility issues.
UAS behavior UAS behavior
1. Inclusion of hi-entry in response has changed from SHOULD to 1. Inclusion of hi-entry in response has changed from SHOULD to
MUST. MUST.
As the entity receiving response with hi-entry expected it with As the entity receiving response with hi-entry expected it with
SHOULD, this change will not cause any backward compatibility issues. SHOULD, this change will not cause any backward compatibility issues.
Proxy/Redirect Server behavior Proxy/Redirect Server behavior
skipping to change at page 31, line 32 skipping to change at page 31, line 10
SHOULD to MUST. SHOULD to MUST.
2. Association of Reason with time-out/internal reason has changed 2. Association of Reason with time-out/internal reason has changed
from MAY to MUST. from MAY to MUST.
3. Inclusion of hi-index has changed from RECOMMENDED to MUST. 3. Inclusion of hi-index has changed from RECOMMENDED to MUST.
4. Inclusion of hi-entries in response has changed from SHOULD to 4. Inclusion of hi-entries in response has changed from SHOULD to
MUST. MUST.
None of the behavior changes will cause any backward compatibility None of above behavior changes impact backwards compatibility since
issues as entity interacting with the updated code, expects the they only strengthen normative behavior to improve interoperability.
values set by the revised behavior anyway.
17. Changes since last Version
NOTE TO THE RFC-Editor: Please remove this section prior to
publication as an RFC.
Changes from 04 to 05:
1. Lots of editorial corrections/clarifications per John Elwell's
comment.
2. Updated Reason header section 10.2 to be consistent (i.e.,
removed references to retargeting) with section 9.3 (Receiving a
response) where the hi-entries and reason header are added to the
cache.
3. Updated section 9.3 (receiving responses) to also include
timeouts and updated to reflect that we don't add the Reason
header in the case of 2xx responses.
4. Added text in Security considerations with regards to needing a
Privacy Service per RFC 3323 to ensure that the privacy is
applied.
Changes from 03 to 04:
1. Reorganization of sections per John Elwell's comments - i.e., a
common section for building HI referenced by the UA, Intermediary
and Redirect server sections.
2. Removing the use of "escape" when describing the handling of the
Privacy and Reason header fields.
3. Clarification of TEL URIs in terms of not having a Privacy or
Reason header field in the hi-targeted-to-uri.
Changes from 02 to 03:
1. Lots of editorial:
2.
A. Reorganized sections similar to the RFC 4244 order - i.e.,
introduce header field parameters and syntax first, then
describe how the functional entities use the header field.
This removes redundant (and often inconsistent) text
describing the parameters.
B. Expanded use of "header" to "header field"
C. More precision in terms of "escaping" of the Privacy and
Reason headers in the hi-targeted-to-uri (versus
"adding"/"setting"/etc. them to the hi-entry).
D. Consistent use of parameter names (i.e., hi-entry versus
entry, hi-target versus target, etc.)
E. Moved item 6 in the Index section to the section on Response
handling
F. Removed last remaining vestiges of inline references to
requirements.
3. Clarifications of functionality/applicability including:
4.
A. which messages may contain History-Info
B. removing security text with regards to being able to figure
out if there are missing entries when using TLS (issue #44)
C. More complete information on the new header field parameters
as they relate to the hi-target parameter.
D. Changed wording from passive to active for normative
statements in many cases and removed superfluous normative
language.
5. Rewrite of the Privacy section to address issues and splitting
into the setting of the Privacy header fields and the processing/
application of the privacy header field priv-values.
6. Rewrite of the Reason header field section - simplifying the text
and adding back the RFC 4244 text with regards to the use of the
Reason header field in cases of internal retargeting.
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 retargeting" 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 field 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
header fields. [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:
1. Moved examples (except first) in appendix to a new
(informational) document.
2. Updated UAS and UAC sections to clarify and expand on the
handling of the History-Info header field.
3. Updated the Application considerations section:
o Included more detail with regards to how applications can make use
of the information, in particular based on the new tags.
o Removed privacy consideration (2nd bullet) since privacy is now
accomplished by anonymizing rather than removal of entries.
Changes from (individual) barnes-sipcore-4244bis-03 to (WG) ietf-
sipcore-4244bis-00:
1. Added a new SIP/SIPS URI parameter to tag the URIs as they are
added to the target list and those returned in the contact header
in a 3xx response.
2. Updated description of "target" parameter to use the new URI
parameter value in setting the value for the parameter.
3. Clarified privacy.
4. Changed handling at redirect server to include the use of the new
URI parameter and to remove the functionality of adding the
History-Info entries (basically reverting to core 4244
processing).
5. Additional text to clarify that a service such as voicemail can
be done in multiple ways.
6. Editorial changes including removal of some vestiges of tagging
all entries (including the "aor" tag).
Changes from barnes-sipcore-4244bis-02 to 03:
1. Fixed problem with indices in example in voicemail example.
2. Removed oc and rt from the Hi-target parameter.
3. Removed aor tag
4. Added index parameter to "mp"
5. Added use-cases and call-flows from target-uri into appendix.
Changes from barnes-sipcore-4244bis-01 to 02:
1. Added hi-aor parameter that gets marked on the "incoming" hi-
entry.
2. Hi-target parameter defined to be either rc, oc, mp, rt, and now
gets included when adding an hi-entry.
3. Added section on backwards compatibility, as well as added the
recognition and handling of requests that do not support this
specification in the appropriate sections.
4. Updated redirect server/3xx handling to support the new
parameters - i.e., the redirecting entity must add the new hi-
entry since the proxy does not have access to the information as
to how the Contact was determined.
5. Added section on normative differences between this specification
and RFC 4244.
6. Restructuring of document to be more in line with current IETF
practices.
7. Moved Requirements section into an Appendix.
8. Fixed ABNF to remove unintended ordering requirement on hi-index
that was introduced in attempting to illustrate it was a
mandatory parameter.
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-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:
1. Added tags for each type of retargeting including proxy hops,
etc. - i.e., a tag is defined for each specific mechanism by
which the new Request-URI is determined. Note, this is
extremely helpful in terms of backwards compatibility.
2. Fixed all the examples. Made sure loose routing was used in all
of them.
3. Removed example where a proxy using strict routing is using
History-Info for avoiding trying same route twice.
4. Remove redundant Redirect Server example.
5. Index is now mandated to start at "1" instead of recommended.
6. Updated 3xx behavior as the entity sending the 3XX response MUST
add the hi-target attribute to the previous hi-entry to ensure
that it is appropriately tagged (i.e., it's the only one that
knows how the contact in the 3xx was determined.)
7. Removed lots of ambiguity by making many "MAYs" into "SHOULDs"
and some "SHOULDs" into "MUSTs".
8. Privacy is now recommended to be done by anonymizing entries as
per RFC 3323 instead of by removing or omitting hi-entry(s).
9. Requirement for TLS is now same level as per RFC 3261.
10. Clarified behavior for "Privacy" (i.e., that Privacy is for Hi-
entries, not headers).
11. Removed "OPTIONALITY" as specific requirements, since it's
rather superflous.
12. Other editorial changes to remove redundant text/sections.
Changes from RFC4244 to barnes-sip-4244bis-00:
1. Clarified that HI captures both retargeting as well as cases of
just forwarding a request.
2. Added descriptions of the usage of the terms "retarget",
"forward" and "redirect" to the terminology section.
3. Added additional examples for the functionality provided by HI
for core SIP.
4. Added hi-target parameter values to HI header to ABNF and
protocol description, as well as defining proxy, UAC and UAS
behavior for the parameter.
5. Simplified example call flow in section 4.5. Moved previous call
flow to appendix.
6. Fixed ABNF per RFC4244 errata "dot" -> "." and added new In cases where an entity that is compliant to this document, receives
parameter. a request that contains hi-entries compliant only to RFC4244 (i.e,
the hi-entries do not contain any of the new header field
parameters), the entity should not make any changes to the hi-entries
- i.e., the entries should be cached and forwarded as any other
entries are. As with RFC4244 compliant entities, applications must
be able to function in cases of missing information. The same
applies to this document as specified in Section 11.
18. References 17. References
18.1. Normative References 17.1. 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 39, line 5 skipping to change at page 32, line 5
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008. Specifications: ABNF", STD 68, RFC 5234, January 2008.
[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.
18.2. Informative References 17.2. 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.
skipping to change at page 39, line 33 skipping to change at page 32, line 33
BCP 99, RFC 3969, December 2004. BCP 99, RFC 3969, December 2004.
[RFC3966] Schulzrinne, H., "The tel URI for Telephone Numbers", [RFC3966] Schulzrinne, H., "The tel URI for Telephone Numbers",
RFC 3966, December 2004. RFC 3966, December 2004.
[RFC4458] Jennings, C., Audet, F., and J. Elwell, "Session [RFC4458] Jennings, C., Audet, F., and J. Elwell, "Session
Initiation Protocol (SIP) URIs for Applications such as Initiation Protocol (SIP) URIs for Applications such as
Voicemail and Interactive Voice Response (IVR)", RFC 4458, Voicemail and Interactive Voice Response (IVR)", RFC 4458,
April 2006. April 2006.
[I-D.barnes-sipcore-rfc4244bis-callflows]
Barnes, M., Audet, F., Schubert, S., Elburg, H., and C.
Holmberg, "Session Initiation Protocol (SIP) History-Info
Header Call Flow Examples",
draft-barnes-sipcore-rfc4244bis-callflows-03 (work in
progress), March 2012.
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
skipping to change at page 42, line 5 skipping to change at page 35, line 15
2. PRIV-req-2: The entity receiving the Request History must 2. PRIV-req-2: The entity receiving the Request History must
maintain the privacy associated with the information. In maintain the privacy associated with the information. In
addition, local policy at a proxy may identify privacy addition, local policy at a proxy may identify privacy
requirements associated with the Request-URI being captured in requirements associated with the Request-URI being captured in
the Request History information. the Request History information.
3. PRIV-req-3: Request History information subject to privacy shall 3. PRIV-req-3: Request History information subject to privacy shall
not be included in out going messages unless it is protected as not be included in out going messages unless it is protected as
described in [RFC3323]. described in [RFC3323].
Appendix B. Example call flows
The scenarios in this section provide sample use cases for the
History-Info header field for informational purposes only. They are
not intended to be normative. A basic forking use case is included,
along with two use cases illustrating the use of the privacy.
B.1. PBX Voicemail call flow
In this example, Alice calls Bob, whose SIP client is forwarded to
Carol. Carol does not answer the call, thus it is forwarded to a VM
(voicemail) server (VMS). In order to determine the appropriate
mailbox to use for this call, the VMS needs the original target for
the request. The original target is determined by finding the first
hi-entry tagged with "rc" and using the hi-entry referenced by the
index of "rc" header field parameter as the target for determining
the appropriate mailbox. This hi-entry is used to populate the
"target" URI parameter as defined in [RFC4458]. The reason
associated with the first hi-entry tagged with "rc" (i.e., 302) could
be used to provide a customized voicemail greeting and is used to
populate the "cause" URI parameter as defined in [RFC4458]. Note
that some VMSs may also (or instead) use the information available in
the History-Info headers for custom handling of the VM in terms of
how and why the call arrived at the VMS.
Furthermore it is the proxy forwarding the call to VMS that
determines the target of the voicemail, it is the proxy that sets the
target of voicemail which is also the entity that utilizes RFC4244bis
to find the target which is usually based on local policy installed
by the user or an administrator.
Alice example.com Bob Carol VM
| INVITE F1 | | | |
|------------->| | | |
| | INVITE F2 | | |
| |------------->| | |
| | | | |
| 100 Trying | | | |
|<-------------| 302 Moved Temporarily F3 | |
| |<-------------| | |
| | ACK | | |
| |------------->| | |
| | | | |
| | INVITE F4 | | |
| |--------------------------->| |
| | | | |
| | 180 Ringing F5 | |
| |<---------------------------| |
| | | | |
| 180 Ringing | | | |
|<-------------| | | |
| | | | |
| | (timeout) | |
| | | | |
| | INVITE F6 | | |
| |-------------------------------------->|
| | | | |
| | 200 OK F7 |
| |<--------------------------------------|
| 200 OK | | | |
|<-------------| | | |
| | | | |
| ACK | | | |
|------------->| ACK |
| |-------------------------------------->|
F1 INVITE Alice -> Example.com
INVITE sip:bob@example.com
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@example.com>;tag=kkaz-
To: Bob <sip:bob@example.com>
Supported: histinfo
Call-Id: 12345600@example.com
CSeq: 1 INVITE
Contact: Alice <sip:alice@192.0.2.3>
Content-Length: <appropriate value>
[SDP Not Shown]
F2 INVITE Example.com -> Bob
INVITE sip:bob@192.0.2.5 SIP/2.0
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bK12se
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@example.com>;tag=kkaz-
To: Bob <sip:bob@example.com>
Supported: histinfo
Call-Id: 12345600@example.com
CSeq: 1 INVITE
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.5>;index=1.1;rc=1
Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp
Content-Length: <appropriate value>
[SDP Not Shown]
F3 302 Moved Temporarily Bob -> Example.com
SIP/2.0 302 Moved Temporarily
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bK12se
;received=192.0.2.112
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@example.com>;tag=kkaz-
To: Bob <sip:bob@example.com>;tag=2hi-1nf
Supported: histinfo
Call-Id: 12345600@example.com
CSeq: 1 INVITE
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.5>;index=1.1;rc=1
Contact: <sip:carol@example.com>
Content-Type: application/sdp
Content-Length: <appropriate value>
[SDP Not Shown]
F4 INVITE Example.com -> Carol
INVITE sip:carol@192.0.2.4 SIP/2.0
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bK353s
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@example.com>;tag=kkaz-
To: Bob <sip:bob@example.com>
Supported: histinfo
Call-Id: 12345600@example.com
CSeq: 1 INVITE
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.5?Reason=SIP%3Bcause%3D302>;\
index=1.1;rc=1
History-Info: <sip:carol@example.com>;index=1.2;mp=1
History-Info: <sip:carol@192.0.2.4>;index=1.2.1;rc=1.2
Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp
Content-Length: <appropriate value>
[SDP Not Shown]
F5 180 Ringing Carol -> Example.com
SIP/2.0 180 Ringing
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bK353s
;received=192.0.2.113
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@example.com>;tag=kkaz-
To: Bob <sip:bob@example.com>;tag=setss3x
Supported: histinfo
Call-Id: 12345600@example.com
CSeq: 1 INVITE
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.5?Reason=SIP%3Bcause%3D302>;\
index=1.1;rc=1
History-Info: <sip:carol@example.com>;index=1.2;mp=1
History-Info: <sip:carol@192.0.2.4>;index=1.2.1;rc=1.2
Contact: <sip:carol@example.com>
Content-Type: application/sdp
Content-Length: <appropriate value>
[SDP Not Shown]
F6 INVITE Example.com -> VM
INVITE sip:vm@192.0.2.6;target=sip:bob%40example.com;cause=408
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bK12se
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@example.com>;tag=kkaz-
To: Bob <sip:bob@example.com>
Supported: histinfo
Call-Id: 12345600@example.com
CSeq: 1 INVITE
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.5?Reason=SIP%3Bcause%3D302>;\
index=1.1;rc=1
History-Info: <sip:carol@example.com>;index=1.2;mp=1
History-Info: <sip:carol@192.0.2.4?Reason=SIP%3Bcause%3D408>;\
index=1.2.1;rc=1.2
History-Info: <sip:vm@example.com;\
target=sip:bob%40example.com;cause=408>;\
index=1.3;mp=1.2
History-Info: <sip:vm@192.0.2.6;\
target=sip:bob%40example.com;cause=408>;\
index=1.3.1;rc=1.3
Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp
Content-Length: <appropriate value>
[SDP Not Shown]
F7 200 OK VM -> Example.com
SIP/2.0 200 OK
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bK12se
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
;received=192.0.2.114
From: Alice <sip:alice@example.com>;tag=kkaz-
To: Bob <sip:bob@example.com>;tag=3dweggs
Supported: histinfo
Call-Id: 12345600@example.com
CSeq: 1 INVITE
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.5?Reason=SIP%3Bcause%3D302>;\
index=1.1;rc=1
History-Info: <sip:carol@example.com>;index=1.2;mp=1
History-Info: <sip:carol@192.0.2.4?Reason=SIP%3Bcause%3D408>;\
index=1.2.1;rc=1.2
History-Info: <sip:vm@example.com;\
target=sip:bob%40example.com;cause=408>;\
index=1.3;mp=1.2
History-Info: <sip:vm@192.0.2.6;\
target=sip:bob%40example.com;cause=408>;\
index=1.3.1;rc=1.3
Contact: <sip:vm@192.0.2.6>
Content-Type: application/sdp
Content-Length: <appropriate value>
[SDP Not Shown]
B.2. Consumer Voicemail example call flow
In this example, Alice calls the Bob but Bob has temporarily
forwarded his phone to Carol because she is his wife. Carol does not
answer the call, thus it is forwarded to a VM (voicemail) server
(VMS). In order to determine the appropriate mailbox to use for this
call, the VMS needs the appropriate target for the request. The last
target is determined by finding the hi-entry referenced by the index
of last hi-entry tagged with "rc" for determining the appropriate
mailbox. This hi-entry is used to populate the "target" URI
parameter as defined in [RFC4458]. Note that some VMSs may also (or
instead) use the information available in the History-Info headers
for custom handling of the VM in terms of how and why the called
arrived at the VMS.
Alice example.com Bob Carol VM
| INVITE F1 | | | |
|------------->| | | |
| | INVITE F2 | | |
| |------------->| | |
| | | | |
| 100 Trying | | | |
|<-------------| 302 Moved Temporarily F3 | |
| |<-------------| | |
| | ACK | | |
| |------------->| | |
| | | | |
| | INVITE F5 | | |
| |--------------------------->| |
| | | | |
| | 180 Ringing F6 | |
| |<---------------------------| |
| | | | |
| 180 Ringing | | | |
|<-------------| | | |
| | | | |
| | (timeout) | |
| | | | |
| | INVITE F7 | | |
| |-------------------------------------->|
| | | | |
| | 200 OK F8 |
| |<--------------------------------------|
| 200 OK | | | |
|<-------------| | | |
| | | | |
| ACK | | | |
|------------->| ACK |
| |-------------------------------------->|
F1 INVITE Alice -> Example.com
INVITE sip:bob@example.com
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@example.com>;tag=kkaz-
To: Bob <sip:bob@example.com>
Supported: histinfo
Call-Id: 12345600@example.com
CSeq: 1 INVITE
Contact: Alice <sip:alice@192.0.2.3>
Content-Length: <appropriate value>
[SDP Not Shown]
F2 INVITE Example.com -> Bob
INVITE sip:bob@192.0.2.5 SIP/2.0
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bK12se
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@example.com>;tag=kkaz-
To: Bob <sip:bob@example.com>
Supported: histinfo
Call-Id: 12345600@example.com
CSeq: 1 INVITE
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.5>;index=1.1;rc=1
Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp
Content-Length: <appropriate value>
[SDP Not Shown]
F3 302 Moved Temporarily Bob -> Example.com
SIP/2.0 302 Moved Temporarily
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bK12se
;received=192.0.2.111
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@example.com>;tag=kkaz-
To: Bob <sip:bob@example.com>;tag=2hi1nfo
Supported: histinfo
Call-Id: 12345600@example.com
CSeq: 1 INVITE
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.5>;index=1.1;rc=1
Contact: <sip:carol@example.com>
Content-Type: application/sdp
Content-Length: <appropriate value>
[SDP Not Shown]
F4 INVITE Example.com -> Carol
INVITE sip:carol@192.0.2.4 SIP/2.0
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bKseb1
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@example.com>;tag=kkaz-
To: Bob <sip:bob@example.com>
Supported: histinfo
Call-Id: 12345600@example.com
CSeq: 1 INVITE
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.5?Reason=SIP%3Bcause%3D302>;\
index=1.1;rc=1
History-Info: <sip:carol@example.com>;index=1.2;mp=1
History-Info: <sip:carol@192.0.2.4>;index=1.2.1;rc=1.2
Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp
Content-Length: <appropriate value>
[SDP Not Shown]
F5 180 Ringing Carol -> Example.com
SIP/2.0 180 Ringing
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bKseb1
;received=192.0.2.112
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@example.com>;tag=kkaz-
To: Bob <sip:bob@example.com>;tag=setss3x
Supported: histinfo
Call-Id: 12345600@example.com
CSeq: 1 INVITE
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.5?Reason=SIP%3Bcause%3D302>;\
index=1.1;rc=1
History-Info: <sip:carol@example.com>;index=1.2;mp=1
History-Info: <sip:carol@192.0.2.4>;index=1.2.1;rc=1.2
Contact: Carol <sip:carol@192.0.2.4>
Content-Type: application/sdp
Content-Length: <appropriate value>
[SDP Not Shown]
F6 INVITE Example.com -> VM
INVITE sip:vm@192.0.2.6;target=sip:carol%40example.com
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bKb3ss
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@example.com>;tag=kkaz-
To: Bob <sip:bob@example.com>
Supported: histinfo
Call-Id: 12345600@example.com
CSeq: 1 INVITE
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.5?Reason=SIP%3Bcause%3D302>;\
index=1.1;rc
History-Info: <sip:carol@example.com?Reason=SIP%3Bcause%3D408>;\
index=1.2;mp=1
History-Info: <sip:carol@192.0.2.4>;index=1.2.1;rc=1.2
History-Info: <sip:vm@example.com;target=sip:carol%40example.com>;\
index=1.3;mp=1.2
History-Info: <sip:vm@192.0.2.5;target=sip:carol%40example.com>;\
index=1.3.1
Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp
Content-Length: <appropriate value>
[SDP Not Shown]
F7 200 OK VM -> Example.com
SIP/2.0 200 OK
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bKb3ss
;received=192.0.2.113
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@example.com>;tag=kkaz-
To: Bob <sip:bob@example.com>;tag=3dweggs
Supported: histinfo
Call-Id: 12345600@example.com
CSeq: 1 INVITE
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.5?Reason=SIP%3Bcause%3D302>;\
index=1.1;rc
History-Info: <sip:carol@example.com?Reason=SIP%3Bcause%3D408>;\
index=1.2;mp=1
History-Info: <sip:carol@192.0.2.4>;index=1.2.1;rc=1.2
History-Info: <sip:vm@example.com;target=sip:carol%40example.com>;\
index=1.3;mp=1.2
History-Info: <sip:vm@192.0.2.5;target=sip:carol%40example.com>;\
index=1.3.1
Contact: <sip:vm@192.0.2.6>
Content-Type: application/sdp
Content-Length: <appropriate value>
[SDP Not Shown]
The VMS can look at the last hi-entry and find the target of the
mailbox by looking for the "target" URI parameter in the hi-entry.
B.3. Sequentially Forking (History-Info in Response)
This scenario highlights an example where the History-Info in the
response is useful to an application or user that originated the
request.
Alice sends a call to Bob via sip:example.com. The proxy sip:
example.com sequentially tries Bob on a SIP UA that has bound a
contact with the sip:bob@example.com AOR, and then several alternate
addresses (Office and Home) unsuccessfully before sending a response
to Alice. The hi-entry containing the initial contact is the hi-
entry just prior to the first hi-entry tagged with an "rc" header
field parameter. In this example, the Office and Home are not the
same AOR as sip:bob@example.com, but rather different AORs that have
been configured as alternate addresses for Bob in the proxy. In
other words, Office and Bob are not bound through SIP Registration
with Bob's AOR. This type of arrangement is common for example when
a "routing" rule to a PSTN number is manually configured in a proxy.
These hi-entries are identified by the index contained in the hi-
target-param "mp" header field parameter in the hi-entries.
This scenario illustrates that by providing the History-Info to
Alice, the end-user or an application at Alice could make a decision
on how best to attempt finding Bob without sending multiple requests
to the same destination. Upon receipt of the response containing the
History-Info entries, the Request URIs for the History-Info entries
tagged with "mp" header field parameter are extracted. Those
Request-URIs can be compared to other URIs (if any) that might be
attempted in order to establish the session with Bob. Thus, avoiding
another INVITE to Bob's home phone. Without this mechanism, Alice
might well attempt to reach Bob at his office phone, which would then
retarget the request to Bob's home phone. When that attempt failed,
then Alice might attempt to reach Bob directly at his home phone,
unknowingly for a third time.
Alice example.com Bob Office Home
| | | | |
| INVITE F1 | | | |
|----------->| INVITE F2 | | |
| |----------------->| | |
| 100 Trying F3 | | |
|<-----------| 302 Move Temporarily F4 | |
| |<-----------------| | |
| | ACK F5 | | |
| |----------------->| | |
| | INVITE F6 | |
| |-------------------------->| |
| | 180 Ringing F7 | |
| |<--------------------------| |
| 180 Ringing F8 | |
|<-----------| retransmit INVITE | |
| |-------------------------->| |
| | ( timeout ) | |
| | INVITE F9 |
| |----------------------------------->|
| | 100 Trying F10 |
| |<-----------------------------------|
| | 486 Busy Here F11 |
| |<-----------------------------------|
| 486 Busy Here F12 |
|<-----------| ACK F13 |
| |----------------------------------->|
| ACK F14 | |
|----------->| |
Message Details
F1 INVITE alice -> example.com
INVITE sip:bob@example.com SIP/2.0
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@example.com>;tag=sr3dds
To: Bob <sip:bob@example.com>
Supported: histinfo
Call-Id: 12345600@example.com
CSeq: 1 INVITE
History-Info: <sip:bob@example.com>;index=1
Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp
Content-Length: <appropriate value>
<!-- SDP Not Shown -->
F2 INVITE example.com -> Bob
INVITE sip:bob@192.0.2.4 SIP/2.0
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bKx3st
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@example.com>;tag=sr3dds
To: Bob <sip:bob@example.com>
Supported: histinfo
Call-Id: 12345600@example.com
CSeq: 1 INVITE
Record-Route: <sip:proxy.example.com;lr>
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4>;index=1.1;rc=1
Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp
Content-Length: <appropriate value>
<!-- SDP Not Shown -->
F3 100 Trying example.com -> alice
SIP/2.0 100 Trying
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bKx3st
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@example.com>;tag=sr3dds
To: Bob <sip:bob@example.com>
Call-Id: 12345600@example.com
CSeq: 1 INVITE
Content-Length: 0
F4 302 Moved Temporarily Bob -> example.com
SIP/2.0 302 Moved Temporarily
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bKrs22
;received=192.0.2.111
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@example.com>;tag=sr3dds
To: Bob <sip:bob@example.com>;tag=hi51nfo
Call-Id: 12345600@example.com
CSeq: 1 INVITE
Record-Route: <sip:proxy.example.com;lr>
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4>;index=1.1;rc=1
Contact: <sip:office@example.com>;mp=1
Content-Length: 0
F5 ACK example.com -> Bob
ACK sip:bob@example.com SIP/2.0
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bKrs22
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bKx3st
From: Alice <sip:alice@example.com>;tag=sr3dds
To: Bob <sip:bob@192.0.2.4>;tag=hi51nfo
Call-Id: 12345600@example.com
CSeq: 1 ACK
Content-Length: 0
F6 INVITE example.com -> office
INVITE sip:office@192.0.2.5 SIP/2.0
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bKzeld
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bKbst2
From: Alice <sip:alice@example.com>;tag=sr3dds
To: Bob <sip:bob@example.com>
Supported: histinfo
Call-Id: 12345600@example.com
Record-Route: <sip:proxy.example.com;lr>
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4?Reason=SIP%3Bcause%3D302>;\
index=1.1;rc=1
History-Info: <sip:office@example.com>;index=1.2;mp=1
History-Info: <sip:office@192.0.2.5>;index=1.2.1;rc=1.2
CSeq: 1 INVITE
Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp
Content-Length: <appropriate value>
<!-- SDP Not Shown -->
F7 180 Ringing office -> example.com
SIP/2.0 180 Ringing
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bKzeld
;received=192.0.2.113
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bKbst2
From: Alice <sip:alice@example.com>;tag=sr3dds
To: Bob <sip:bob@example.com>;tag=53rdds
Supported: histinfo
Call-ID: 12345600@example.com
Record-Route: <sip:proxy.example.com;lr>
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4?Reason=SIP%3Bcause%3D302>;\
index=1.1;rc=1
History-Info: <sip:office@example.com>;index=1.2;mp=1
History-Info: <sip:office@192.0.2.5>;index=1.2.1;rc=1.2
CSeq: 1 INVITE
Contact: Office <office@192.0.2.4>
Content-Length: 0
F8 180 Ringing example.com -> alice
SIP/2.0 180 Ringing
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bKbst2
From: Alice <sip:alice@example.com>;tag=sr3dds
To: Bob <sip:bob@example.com>;tag=53rdds
Supported: histinfo
Call-Id: 12345600@example.com
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4?Reason=SIP%3Bcause%3D302>;\
index=1.1;rc=1
History-Info: <sip:office@example.com>;index=1.2;mp=1
History-Info: <sip:office@192.0.2.5>;index=1.2.1;rc=1.2
CSeq: 1 INVITE
Contact: Office <office@192.0.2.4>
Content-Length: 0
F9 INVITE example.com -> home
INVITE sip:home@192.0.2.6 SIP/2.0
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bKx3st
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bKbst2
From: Alice <sip:alice@example.com>;tag=sr3dds
To: Bob <sip:bob@example.com>
Supported: histinfo
Call-Id: 12345600@example.com
Record-Route: <sip:proxy.example.com;lr>
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4?Reason=SIP%3Bcause%3D302>;\
index=1.1;rc=1
History-Info: <sip:office@example.com>;index=1.2;mp=1
History-Info: <sip:office@192.0.2.5?Reason=SIP%3Bcause%3D408>;\
index=1.2.1>;index=1.2.1;rc=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;rc=1.3
CSeq: 1 INVITE
Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp
Content-Length: <appropriate value>
<!-- SDP Not Shown -->
F10 100 Trying home -> example.com
SIP/2.0 100 Trying
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bKx3st
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bKbst2
From: Alice <sip:alice@example.com>;tag=sr3dds
To: Bob <sip:bob@example.com>
Call-Id: 12345600@example.com
CSeq: 1 INVITE
Content-Length: 0
F11 486 Busy Here home -> example.com
SIP/2.0 486 Busy Here
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bKx3st
;received=192.0.2.114
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bKbst2
From: Alice <sip:alice@example.com>;tag=sr3dds
To: Bob <sip:bob@example.com>;tag=53rdds
Call-Id: 12345600@example.com
Record-Route: <sip:proxy.example.com;lr>
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4?Reason=SIP%3Bcause%3D302>;\
index=1.1;rc=1
History-Info: <sip:office@example.com>;index=1.2;mp=1
History-Info: <sip:office@192.0.2.5?Reason=SIP%3Bcause%3D408>;\
index=1.2.1>;index=1.2.1;rc=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;rc=1.3
CSeq: 1 INVITE
Content-Length: 0
F12 486 Busy Here example.com -> alice
SIP/2.0 486 Busy Here
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bKbst2
From: Alice <sip:alice@example.com>;tag=sr3dds
To: Bob <sip:bob@example.com>;tag=53rdds
Call-Id: 12345600@example.com
History-Info: <sip:bob@example.com>;index=1
History-Info: <sip:bob@192.0.2.4?Reason=SIP%3Bcause%3D302>;\
index=1.1;rc=1
History-Info: <sip:office@example.com>;index=1.2;mp=1
History-Info: <sip:office@192.0.2.5?Reason=SIP%3Bcause%3D408>;\
index=1.2.1>;index=1.2.1;rc=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;rc=1.3
CSeq: 1 INVITE
Content-Length: 0
F13 ACK example.com -> home
ACK sip:home@192.0.2.6 SIP/2.0
Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bKx3st
From: Alice <sip:alice@example.com>;tag=sr3dds>;
To: Bob <sip:bob@example.com>;tag=53rdds
Call-Id: 12345600@example.com
CSeq: 1 ACK
Content-Length: 0
F14 ACK alice -> example.com
ACK sip:bob@example.com SIP/2.0
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bKbst2
From: Alice <sip:alice@example.com>;tag=sr3dds
To: Bob <sip:bob@example.com>;tag=53rdds
Call-Id: 12345600@example.com
Route: <sip:proxy.example.com;lr>
CSeq: 1 ACK
Content-Length: 0
B.4. History-Info with Privacy Header Field
This example provides a basic call scenario without forking. Alice
has indicated that she wants Privacy associated with the History-Info
header field entries. In addition, sip:biloxi.example.com adds
Privacy header fields indicating that the History-Info header field
information is anonymized outside the biloxi.example.com domain.
Note, that if the atlanta.example.com proxy had added privacy header
fields to all its hi-entries, then all the hi-entries in the response
would be anonymous.
Alice atlanta.example.com biloxi.example.com Bob
| | | |
| INVITE F1 | | |
|--------------->| | |
| | | |
| | INVITE F2 | |
| |--------------->| |
| | | |
| | | INVITE F3 |
| | |--------------->|
| | | |
| | | 200 F4 |
| | |<---------------|
| | | |
| | 200 F5 | |
| |<---------------| |
| | | |
| 200 F6 | | |
|<---------------| | |
| | | |
| ACK | | |
|--------------->| ACK | |
| |--------------->| ACK |
| | |--------------->|
Figure 2: Example with Privacy Header Fields
Message Details
F1 INVITE alice -> atlanta.example.com
INVITE sip:bob@biloxi.example.com;p=x SIP/2.0
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@atlanta.example.com>;tag=22
To: Bob <sip:bob@biloxi.example.com>
Supported: histinfo
Privacy: History
Call-Id: 12345600@atlanta.example.com
CSeq: 1 INVITE
History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp
Content-Length: <appropriate value>
<!-- SDP Not Shown -->
F2 INVITE atlanta.example.com -> biloxi.example.com
INVITE sip:bob@biloxi.example.com;p=x SIP/2.0
Via: SIP/2.0/TCP proxy.atlanta.example.com:5060;branch=z9hG4bKbst2
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@atlanta.example.com>;tag=22
To: Bob <sip:bob@biloxi.example.com>
Supported: histinfo
Call-Id: 12345600@atlanta.example.com
CSeq: 1 INVITE
History-Info: <sip:anonymous@anonymous.invalid>;index=1
History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1;rc=1
Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp
Content-Length: <appropriate value>
<!-- SDP Not Shown -->
F3 INVITE biloxi.example.com -> Bob
INVITE sip:bob@192.0.1.11 SIP/2.0
Via: SIP/2.0/TCP proxy.biloxi.example.com:5060;branch=z9hG4bKtg3s
Via: SIP/2.0/TCP proxy.atlanta.example.com:5060;branch=z9hG4bKbst2
;received=192.0.2.111
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@atlanta.example.com>;tag=22
To: Bob <sip:bob@biloxi.example.com>
Supported: histinfo
Call-Id: 12345600@atlanta.example.com
CSeq: 1 INVITE
History-Info: <sip:anonymous@anonymous.invalid>;index=1
History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1;rc=1
History-Info: <sip:bob@192.0.1.11?Privacy=history>;index=1.1.1;rc=1.1
Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp
Content-Length: <appropriate value>
<!-- SDP Not Shown -->
F4 200 OK Bob -> biloxi.example.com
SIP/2.0 200 OK
Via: SIP/2.0/TCP proxy.biloxi.example.com:5060;branch=z9hG4bKtg3s
;received=192.0.2.112
Via: SIP/2.0/TCP proxy.atlanta.example.com:5060;branch=z9hG4bKbst2
;received=192.0.2.111
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@atlanta.example.com>;tag=22
To: Bob <sip:bob@biloxi.example.com>;tag=33
Supported: histinfo
Call-Id: 12345600@atlanta.example.com
CSeq: 1 INVITE
History-Info: <sip:anonymous@anonymous.invalid>;index=1
History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1;rc=1
History-Info: <sip:bob@192.0.1.11?Privacy=history>;index=1.1.1;rc=1.1
Contact: Bob <sip:bob@192.0.1.11>
Content-Type: application/sdp
Content-Length: <appropriate value>
<!-- SDP Not Shown -->
F5 200 OK biloxi.example.com -> atlanta.example.com
SIP/2.0 200 OK
Via: SIP/2.0/TCP proxy.atlanta.example.com:5060;branch=z9hG4bKbst2
;received=192.0.2.111
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@atlanta.example.com>;tag=22
To: Bob <sip:bob@biloxi.example.com>;tag=33
Supported: histinfo
Call-Id: 12345600@atlanta.example.com
CSeq: 1 INVITE
History-Info: <sip:anonymous@anonymous.invalid>;index=1
History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1;rc=1
History-Info: <sip:anonymous@anonymous.invalid>;index=1.1.1;rc=1.1
Contact: Bob <sip:bob@192.0.1.11>
Content-Type: application/sdp
Content-Length: <appropriate value>
<!-- SDP Not Shown -->
F6 200 OK atlanta.example.com -> Alice
SIP/2.0 200 OK
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@atlanta.example.com>;tag=22
To: Bob <sip:bob@biloxi.example.com>;tag=33
Supported: histinfo
Call-Id: 12345600@atlanta.example.com
CSeq: 1 INVITE
History-Info: <sip:anonymous@anonymous.invalid>;index=1
History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1;rc=1
History-Info: <sip:anonymous@anonymous.invalidtarget userindex=1.1.1;rc=1.1
Contact: Bob <sip:bob@192.0.1.11>
Content-Type: application/sdp
Content-Length: <appropriate value>
<!-- SDP Not Shown -->
B.5. Privacy for a Specific History-Info Entry
This example provides a basic call scenario similar to Appendix B.4,
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,
contains a privacy header field with a priv-value of "history", thus
providing Alice with some information about the history of the
request, but anonymizing Bob's local URI.
Alice atlanta.example.com biloxi.example.com Bob
| | | |
| INVITE F1 | | |
|--------------->| | |
| | | |
| | INVITE F2 | |
| |--------------->| |
| | | |
| | | INVITE F3 |
| | |--------------->|
| | | |
| | | 200 F4 |
| | |<---------------|
| | | |
| | 200 F5 | |
| |<---------------| |
| | | |
| 200 F6 | | |
|<---------------| | |
| | | |
| ACK | | |
|--------------->| ACK | |
| |--------------->| ACK |
| | |--------------->|
Figure 3: Example with Privacy Header Field for Specific URI
Message Details
F1 INVITE alice -> atlanta.example.com
INVITE sip:bob@biloxi.example.com;p=x SIP/2.0
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@atlanta.example.com>;tag=22
To: Bob <sip:bob@biloxi.example.com>
Supported: histinfo
Call-Id: 12345600@atlanta.example.com
CSeq: 1 INVITE
History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp
Content-Length: <appropriate value>
<!-- SDP Not Shown -->
F2 INVITE atlanta.example.com -> biloxi.example.com
INVITE sip:bob@biloxi.example.com;p=x SIP/2.0
Via: SIP/2.0/TCP proxy.atlanta.example.com:5060;branch=z9hG4bKbst2
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@atlanta.example.com>;tag=22
To: Bob <sip:bob@biloxi.example.com>
Supported: histinfo
Call-Id: 12345600@atlanta.example.com
CSeq: 1 INVITE
History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1;rc=1
Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp
Content-Length: <appropriate value>
<!-- SDP Not Shown -->
F3 INVITE biloxi.example.com -> Bob
INVITE sip:bob@192.0.1.11 SIP/2.0
Via: SIP/2.0/TCP proxy.biloxi.example.com:5060;branch=z9hG4bKeset
Via: SIP/2.0/TCP proxy.atlanta.example.com:5060;branch=z9hG4bKbst2
;received=192.0.2.112
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@atlanta.example.com>;tag=22
To: Bob <sip:bob@biloxi.example.com>
Supported: histinfo
Call-Id: 12345600@atlanta.example.com
CSeq: 1 INVITE
History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1;rc=1
History-Info: <sip:bob@192.0.1.11?Privacy=history>;index=1.1.1;rc=1.1
Contact: Alice <sip:alice@192.0.2.3>
Content-Type: application/sdp
Content-Length: <appropriate value>
<!-- SDP Not Shown -->
F4 200 OK Bob -> biloxi.example.com
SIP/2.0 200 OK
Via: SIP/2.0/TCP proxy.biloxi.example.com:5060;branch=z9hG4bKeset
;received=192.0.2.111
Via: SIP/2.0/TCP proxy.atlanta.example.com:5060;branch=z9hG4bKbst2
;received=192.0.2.112
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@atlanta.example.com>;tag=22
To: Bob <sip:bob@biloxi.example.com>;tag=33
Supported: histinfo
Call-Id: 12345600@atlanta.example.com
CSeq: 1 INVITE
History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1;rc=1
History-Info: <sip:bob@192.0.1.11?Privacy=history>;index=1.1.1;rc=1.1
Contact: Bob <sip:bob@192.0.1.11>
Content-Type: application/sdp
Content-Length: <appropriate value>
<!-- SDP Not Shown -->
F5 200 OK biloxi.example.com -> atlanta.example.com
SIP/2.0 200 OK
Via: SIP/2.0/TCP proxy.atlanta.example.com:5060;branch=z9hG4bKbst2
;received=192.0.2.112
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@atlanta.example.com>;tag=22
To: Bob <sip:bob@biloxi.example.com>;tag=33
Supported: histinfo
Call-Id: 12345600@atlanta.example.com
CSeq: 1 INVITE
History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1;rc=1
History-Info: <sip:anonymous@anonymous.invalid>;index=1.1.1;rc=1.1
Contact: Bob <sip:bob@192.0.1.11>
Content-Type: application/sdp
Content-Length: <appropriate value>
<!-- SDP Not Shown -->
F6 200 OK atlanta.example.com -> Alice
SIP/2.0 200 OK
Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
From: Alice <sip:alice@atlanta.example.com>;tag=22
To: Bob <sip:bob@biloxi.example.com>;tag=33
Supported: histinfo
Call-Id: 12345600@atlanta.example.com
CSeq: 1 INVITE
History-Info: <sip:bob@biloxi.example.com;p=x>;index=1
History-Info: <sip:bob@biloxi.example.com;p=x>;index=1.1;rc=1
History-Info: <sip:anonymous@anonymous.invalid>;index=1.1.1;rc=1.1
Contact: Bob <sip:bob@192.0.1.11>
Content-Type: application/sdp
Content-Length: <appropriate value>
<!-- SDP Not Shown -->
Authors' Addresses Authors' Addresses
Mary Barnes Mary Barnes
Polycom Polycom
TX TX
US US
Email: mary.ietf.barnes@gmail.com Email: mary.ietf.barnes@gmail.com
Francois Audet Francois Audet
skipping to change at page 67, line 4 skipping to change at page 35, line 33
Francois Audet Francois Audet
Skype Skype
Email: francois.audet@skype.net Email: francois.audet@skype.net
Shida Schubert Shida Schubert
NTT NTT
Email: shida@ntt-at.com Email: shida@ntt-at.com
Hans Erik van Elburg Hans Erik van Elburg
Detecon International Gmbh Detecon International Gmbh
Oberkasseler str. 2 Sternengasse 14-16
Bonn, Cologne,
Germany Germany
Email: ietf.hanserik@gmail.com Email: ietf.hanserik@gmail.com
Christer Holmberg Christer Holmberg
Ericsson Ericsson
Hirsalantie 11, Jorvas Hirsalantie 11, Jorvas
Finland Finland
Email: christer.holmberg@ericsson.com Email: christer.holmberg@ericsson.com
 End of changes. 45 change blocks. 
1435 lines changed or deleted 150 lines changed or added

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