draft-ietf-mmusic-dtls-sdp-11.txt   draft-ietf-mmusic-dtls-sdp-12.txt 
Network Working Group C. Holmberg Network Working Group C. Holmberg
Internet-Draft Ericsson Internet-Draft Ericsson
Updates: 5763,7345 (if approved) R. Shpount Updates: 5763,7345 (if approved) R. Shpount
Intended status: Standards Track TurboBridge Intended status: Standards Track TurboBridge
Expires: September 22, 2016 March 21, 2016 Expires: November 22, 2016 May 21, 2016
Using the SDP Offer/Answer Mechanism for DTLS Using the SDP Offer/Answer Mechanism for DTLS
draft-ietf-mmusic-dtls-sdp-11.txt draft-ietf-mmusic-dtls-sdp-12.txt
Abstract Abstract
This draft defines the SDP offer/answer procedures for negotiating This draft defines the SDP offer/answer procedures for negotiating
and establishing a DTLS association. The draft also defines the and establishing a DTLS association. The draft also defines the
criteria for when a new DTLS association must be established. criteria for when a new DTLS association must be established.
This draft defines a new SDP media-level attribute, 'dtls- This draft defines a new SDP media-level attribute, 'dtls-id'.
association-id'.
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 September 22, 2016. This Internet-Draft will expire on November 22, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 15 skipping to change at page 2, line 15
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Establishing a new DTLS Association . . . . . . . . . . . . . 3 3. Establishing a new DTLS Association . . . . . . . . . . . . . 3
3.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2. Change of Local Transport Parameters . . . . . . . . . . 4 3.2. Change of Local Transport Parameters . . . . . . . . . . 4
3.3. Change of ICE ufrag value . . . . . . . . . . . . . . . . 4 3.3. Change of ICE ufrag value . . . . . . . . . . . . . . . . 4
4. SDP dtls-association-id Attribute . . . . . . . . . . . . . . 4 4. SDP dtls-id Attribute . . . . . . . . . . . . . . . . . . . . 4
5. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 5 5. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 5
5.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 5 5.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.2. Generating the Initial SDP Offer . . . . . . . . . . . . 7 5.2. Generating the Initial SDP Offer . . . . . . . . . . . . 7
5.3. Generating the Answer . . . . . . . . . . . . . . . . . . 7 5.3. Generating the Answer . . . . . . . . . . . . . . . . . . 7
5.4. Offerer Processing of the SDP Answer . . . . . . . . . . 8 5.4. Offerer Processing of the SDP Answer . . . . . . . . . . 8
5.5. Modifying the Session . . . . . . . . . . . . . . . . . . 8 5.5. Modifying the Session . . . . . . . . . . . . . . . . . . 9
6. ICE Considerations . . . . . . . . . . . . . . . . . . . . . 9 6. ICE Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Transport Protocol Considerations . . . . . . . . . . . . . . 9 7. Transport Protocol Considerations . . . . . . . . . . . . . . 10
7.1. Transport Re-Usage . . . . . . . . . . . . . . . . . . . 9 7.1. Transport Re-Usage . . . . . . . . . . . . . . . . . . . 10
8. SIP Considerations . . . . . . . . . . . . . . . . . . . . . 9 8. SIP Considerations . . . . . . . . . . . . . . . . . . . . . 10
9. RFC Updates . . . . . . . . . . . . . . . . . . . . . . . . . 10 9. RFC Updates . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 10 9.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.2. Update to RFC 5763 . . . . . . . . . . . . . . . . . . . 10 9.2. Update to RFC 5763 . . . . . . . . . . . . . . . . . . . 11
9.3. Update to RFC 7345 . . . . . . . . . . . . . . . . . . . 15 9.3. Update to RFC 7345 . . . . . . . . . . . . . . . . . . . 16
10. Security Considerations . . . . . . . . . . . . . . . . . . . 18 10. Security Considerations . . . . . . . . . . . . . . . . . . . 19
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19
13. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 19 13. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 19
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 22
14.1. Normative References . . . . . . . . . . . . . . . . . . 21 14.1. Normative References . . . . . . . . . . . . . . . . . . 22
14.2. Informative References . . . . . . . . . . . . . . . . . 22 14.2. Informative References . . . . . . . . . . . . . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23
1. Introduction 1. Introduction
[RFC5763] defines SDP Offer/Answer procedures for SRTP-DTLS. [RFC5763] defines SDP Offer/Answer procedures for SRTP-DTLS.
[RFC7345] defines SDP Offer/Answer procedures for UDPTL-DTLS. This [RFC7345] defines SDP offer/answer procedures for UDPTL-DTLS. This
specification defines general Offer/Answer procedures for DTLS, based specification defines general offer/answer procedures for DTLS, based
on the procedures in [RFC5763]. Other specifications, defining on the procedures in [RFC5763]. Other specifications, defining
specific DTLS usages, can then reference this specification, in order specific DTLS usages, can then reference this specification, in order
to ensure that the DTLS aspects are common among all usages. Having to ensure that the DTLS aspects are common among all usages. Having
common procedures is essential when multiple usages share the same common procedures is essential when multiple usages share the same
DTLS association [I-D.ietf-mmusic-sdp-bundle-negotiation]. DTLS association [I-D.ietf-mmusic-sdp-bundle-negotiation].
As defined in [RFC5763], a new DTLS association MUST be established As defined in [RFC5763], a new DTLS association MUST be established
when transport parameters are changed. Transport parameter change is when transport parameters are changed. Transport parameter change is
not well defined when Interactive Connectivity Establishment (ICE) not well defined when Interactive Connectivity Establishment (ICE)
[RFC5245] is used. One possible way to determine a transport change [RFC5245] is used. One possible way to determine a transport change
is based on ufrag change, but the ufrag value is changed both when is based on ufrag change, but the ufrag value is changed both when
ICE is negotiated and when ICE restart [RFC5245] occurs. These ICE is negotiated and when ICE restart [RFC5245] occurs. These
events do not always require a new DTLS association to be events do not always require a new DTLS association to be
established, but currently there is no way to explicitly indicate in established, but currently there is no way to explicitly indicate in
an SDP offer or answer whether a new DTLS association is required. an SDP offer or answer whether a new DTLS association is required.
To solve that problem, this draft defines a new SDP attribute, 'dtls- To solve that problem, this draft defines a new SDP attribute, 'dtls-
association-id'. The attribute contains a unique value associated id'. The attribute contains a unique value associated with a DTLS
with a DTLS association, and by providing a new value in SDP offers association, and by providing a new value in SDP offers and answers
and answers the attribute can be used to indicate whether a new DTLS the attribute can be used to indicate whether a new DTLS association
association is to be established/re-established. is to be established/re-established.
2. Conventions 2. Conventions
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].
3. Establishing a new DTLS Association 3. Establishing a new DTLS Association
3.1. General 3.1. General
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Section 5. Section 5.
The sections below describe typical cases where a new DTLS The sections below describe typical cases where a new DTLS
association needs to be established. association needs to be established.
3.2. Change of Local Transport Parameters 3.2. Change of Local Transport Parameters
If an endpoint modifies its local transport parameters (address and/ If an endpoint modifies its local transport parameters (address and/
or port), and if the modification requires a new DTLS association, or port), and if the modification requires a new DTLS association,
the endpoint MUST change its DTLS role, change its fingerprint value, the endpoint MUST change its DTLS role, change its fingerprint value,
and/or use the SDP 'dtls-association-id' attribute with a new value and/or use the SDP 'dtls-id' attribute with a new value Section 4.
Section 4.
If the underlying transport explicitly prohibits a DTLS association If the underlying transport explicitly prohibits a DTLS association
to span multiple transports, and if the transport is changed, a new to span multiple transports, and if the transport is changed, a new
value MUST be assigned to the the SDP 'dtls-association-id' value MUST be assigned to the the SDP 'dtls-id' attribute. An
attribute. An example of such case is when DTLS is carried over example of such case is when DTLS is carried over SCTP, as described
SCTP, as described in [RFC6083]. in [RFC6083].
3.3. Change of ICE ufrag value 3.3. Change of ICE ufrag value
If an endpoint uses ICE, and modifies a local ufrag value, and if the If an endpoint uses ICE, and modifies a local ufrag value, and if the
modification requires a new DTLS association, the endpoint MUST modification requires a new DTLS association, the endpoint MUST
either change its DTLS role, a fingerprint value and/or assign a new either change its DTLS role, a fingerprint value and/or assign a new
value to the SDP 'dtls-association-id' attribute Section 4. value to the SDP 'dtls-id' attribute Section 4.
4. SDP dtls-association-id Attribute 4. SDP dtls-id Attribute
The SDP 'dtls-association-id' attribute contains a unique value The SDP 'dtls-id' attribute contains a unique value associated with a
associated with a DTLS association. DTLS association.
Name: dtls-association-id Name: dtls-id
Value: conn-value Value: conn-value
Usage Level: media Usage Level: media
Charset Dependent: no Charset Dependent: no
Syntax: Syntax:
conn-value = 1*256alphanum conn-value = 1*256alphanum
Example: Example:
a=dtls-association-id:abc3dl a=dtls-id:abc3dl
A 'dtls-association-id' attribute that contains a new value indicates A 'dtls-id' attribute that contains a new value indicates an
an intention to establish a new DTLS association. A 'dtls- intention to establish a new DTLS association. A 'dtls-id' attribute
association-id' attribute that contains a previously assigned value that contains a previously assigned value indicates an intention to
indicates an intention to reuse an existing association. reuse an existing association.
There is no default value defined for the SDP 'dtls-association-id' There is no default value defined for the SDP 'dtls-id' attribute.
attribute. Implementations that wish to use the attribute MUST Implementations that wish to use the attribute MUST explicitly
explicitly include it in SDP offers and answers. If an offer or include it in SDP offers and answers. If an offer or answer does not
answer does not contain an attribute (this could happen if the contain an attribute (this could happen if the offerer or answerer
offerer or answerer represents an existing implementation that has represents an existing implementation that has not been updated to
not been updated to support the attribute defined in this support the attribute defined in this specification or an
specification or an implementation which allocates a new temporary implementation which allocates a new temporary certificate for each
certificate for each association and uses change in fingerprint to association and uses change in fingerprint to indicate new
indicate new association), other means needs to be used in order for association), other means needs to be used in order for endpoints to
endpoints to determine whether an offer or answer is associated with determine whether an offer or answer is associated with an event that
an event that requires the DTLS association to be re-established. requires the DTLS association to be re-established.
The mux category [I-D.ietf-mmusic-sdp-mux-attributes] for the 'dtls- The mux category [I-D.ietf-mmusic-sdp-mux-attributes] for the 'dtls-
association-id' attribute is 'IDENTICAL', which means that the id' attribute is 'IDENTICAL', which means that the attribute value
attribute value must be identical across all media descriptions being must be identical across all media descriptions being multiplexed
multiplexed [I-D.ietf-mmusic-sdp-bundle-negotiation]. [I-D.ietf-mmusic-sdp-bundle-negotiation].
For RTP-based media, the 'dtls-association-id' attribute apply to For RTP-based media, the 'dtls-id' attribute apply to whole
whole associated media description. The attribute MUST NOT be associated media description. The attribute MUST NOT be defined per
defined per source (using the SDP 'ssrc' attribute [RFC5576]). source (using the SDP 'ssrc' attribute [RFC5576]).
The SDP Offer/Answer [RFC3264] procedures associated with the The SDP offer/answer [RFC3264] procedures associated with the
attribute are defined in Section 5 attribute are defined in Section 5
5. SDP Offer/Answer Procedures 5. SDP Offer/Answer Procedures
5.1. General 5.1. General
This section defines the generic SDP offer/answer procedures for This section defines the generic SDP offer/answer procedures for
negotiating a DTLS association. Additional procedures (e.g. negotiating a DTLS association. Additional procedures (e.g.
regarding usage of specific SDP attributes etc) for individual DTLS regarding usage of specific SDP attributes etc) for individual DTLS
usages (e.g. SRTP-DTLS) are outside the scope of this specification, usages (e.g. SRTP-DTLS) are outside the scope of this specification,
and need to be specified in a usage specific specification. and need to be specified in a usage specific specification.
NOTE: The procedures in this section are generalizations of NOTE: The procedures in this section are generalizations of
procedures first specified in SRTP-DTLS [RFC5763], with the addition procedures first specified in SRTP-DTLS [RFC5763], with the addition
of usage of the SDP 'dtls-association-id' attribute. That document of usage of the SDP 'dtls-id' attribute. That document is herein
is herein revised to make use of these new procedures. revised to make use of these new procedures.
The procedures in this section apply to an SDP media description The procedures in this section apply to an SDP media description
("m=" line) associated a DTLS-protected media/data stream. ("m=" line) associated a DTLS-protected media/data.
When an offerer needs to establish a new DTLS association, and if an
unreliable transport (e.g. UDP) is used, the offerer MUST allocate a
new transport for the offer in such a way that the offerer can
disambiguate any packets associated with the new DTLS association
from any packets associated with any other DTLS association. This
typically means using a local address and or port, or a set of ICE
candidates (see Section 6), which were not recently used for any
other DTLS association.
When an answerer needs to establish a new DTLS association, if
unreliable transport is used, and if the offerer did not allocate a
new transport, the answerer MUST allocate a new transport for the
offer in answer a way that it can disambiguate any packets associated
with new DTLS association from any packets associated with any other
DTLS association. This typically means using a local address and or
port, or a set of ICE candidates (see Section 6), which were not
recently used for any other DTLS association.
In order to negotiate a DTLS association, the following SDP In order to negotiate a DTLS association, the following SDP
attributes are used: attributes are used:
o The SDP 'setup' attribute, defined in [RFC4145], is used to o The SDP 'setup' attribute, defined in [RFC4145], is used to
negotiate the DTLS roles; negotiate the DTLS roles;
o The SDP 'fingerprint' attribute, defined in [RFC4572], is used to o The SDP 'fingerprint' attribute, defined in [RFC4572], is used to
provide a fingerprint value; and provide a fingerprint value; and
o The SDP 'dtls-association-id' attribute, defined in this o The SDP 'dtls-id' attribute, defined in this specification,
specification, indicates a unique value associated with the DTLS indicates a unique value associated with the DTLS association.
association. The attribute value can be used to explicitly The attribute value can be used to explicitly indicate the
indicate the intention of establishing a new DTLS association. intention of establishing a new DTLS association.
This specification does not define the usage of the SDP 'connection' This specification does not define the usage of the SDP 'connection'
attribute [RFC4145] for negotiating a DTLS connection. However, the attribute [RFC4145] for negotiating a DTLS connection. However, the
attribute MAY be used if the DTLS association is used together with attribute MAY be used if the DTLS association is used together with
another protocol, e.g. SCTP or TCP, for which the usage of the another protocol, e.g. SCTP or TCP, for which the usage of the
attribute has been defined. attribute has been defined.
Unlike for TCP and TLS connections, endpoints MUST NOT use the SDP Unlike for TCP and TLS connections, endpoints MUST NOT use the SDP
'setup' attribute 'holdconn' value when negotiating a DTLS 'setup' attribute 'holdconn' value when negotiating a DTLS
association. association.
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least one of the certificate fingerprints received in SDP least one of the certificate fingerprints received in SDP
'fingerprint' attributes. If no fingerprint matches the hashed 'fingerprint' attributes. If no fingerprint matches the hashed
certificate, then an endpoint MUST tear down the media session certificate, then an endpoint MUST tear down the media session
immediately. Note that it is permissible to wait until the other immediately. Note that it is permissible to wait until the other
side's fingerprint has been received before establishing the side's fingerprint has been received before establishing the
connection; however, this may have undesirable latency effects. connection; however, this may have undesirable latency effects.
SDP offerers and answerers might reuse certificates across multiple SDP offerers and answerers might reuse certificates across multiple
DTLS associations, and provide identical fingerprint values for each DTLS associations, and provide identical fingerprint values for each
DTLS association. It MUST be ensured that the combination of the DTLS association. It MUST be ensured that the combination of the
fingerprint values and the SDP 'dtls-association-id' attribute value fingerprint values and the SDP 'dtls-id' attribute value is unique
is unique across all DTLS associations. across all DTLS associations.
If an SDP offerer or answerer generates a new temporary self-signed If an SDP offerer or answerer generates a new temporary self-signed
certificate for each new DTLS association, they can omit the SDP certificate for each new DTLS association, they can omit the SDP
'dtls-association-id' attribute. 'dtls-id' attribute.
5.2. Generating the Initial SDP Offer 5.2. Generating the Initial SDP Offer
When the offerer sends the initial offer, and the offerer wants to When the offerer sends the initial offer, and the offerer wants to
establish a DTLS association, it MUST insert an SDP 'dtls- establish a DTLS association, it MUST insert an SDP 'dtls-id'
association-id' attribute with a new value in the offer. In attribute with a new value in the offer. In addition, the offerer
addition, the offerer MUST insert an SDP 'setup' attribute according MUST insert an SDP 'setup' attribute according to the procedures in
to the procedures in [RFC4145], and one or more SDP 'fingerprint' [RFC4145], and one or more SDP 'fingerprint' attributes according to
attributes according to the procedures in [RFC4572], in the offer. the procedures in [RFC4572], in the offer.
If the offerer inserts the SDP 'setup' attribute with an 'actpass' or If the offerer inserts the SDP 'setup' attribute with an 'actpass' or
'passive' value, the offerer MUST be prepared to receive a DTLS 'passive' value, the offerer MUST be prepared to receive a DTLS
ClientHello message (if a new DTLS association is established by the ClientHello message (if a new DTLS association is established by the
answerer) from the answerer before it receives the SDP answer. answerer) from the answerer before it receives the SDP answer.
5.3. Generating the Answer 5.3. Generating the Answer
If an answerer receives an offer that contains an SDP 'dtls- If an answerer receives an offer that contains an SDP 'dtls-id'
association-id' attribute with a new value, or if the answerer attribute with a new value, or if the answerer receives an offer that
receives an offer that contains an 'dtls-association-id' attribute contains an 'dtls-id' attribute with a previously assigned value and
with a previously assigned value and the answerer determines (based the answerer determines (based on the criteria for establishing a new
on the criteria for establishing a new DTLS association) that a new DTLS association) that a new DTLS association is to be established,
DTLS association is to be established, the answerer MUST insert a new the answerer MUST insert a new value in the associated answer. In
value in the associated answer. In addition, the answerer MUST addition, the answerer MUST insert an SDP 'setup' attribute according
insert an SDP 'setup' attribute according to the procedures in to the procedures in [RFC4145], and one or more SDP 'fingerprint'
[RFC4145], and one or more SDP 'fingerprint' attributes according to attributes according to the procedures in [RFC4572], in the answer.
the procedures in [RFC4572], in the answer.
If an answerer receives an offer that contains an SDP 'dtls- If an answerer receives an offer that contains an SDP 'dtls-id'
association-id' attribute with a new value, and if the answerer does attribute with a new value, and if the answerer does not accept the
not accept the establishment of a new DTLS association, the answerer establishment of a new DTLS association, the answerer MUST reject the
MUST reject the "m=" lines associated with the suggested DTLS "m=" lines associated with the suggested DTLS association [RFC3264].
association [RFC3264].
If an answerer receives an offer that contains a 'dtls-association- If an answerer receives an offer that contains a 'dtls-id' attribute
id' attribute with a previously assigned value, and if the answerer with a previously assigned value, and if the answerer determines that
determines that a new DTLS association is not to be established, the a new DTLS association is not to be established, the answerer MUST
answerer MUST insert a 'dtls-association-id' attribute with the insert a 'dtls-id' attribute with the previously assigned value in
previously assigned value in the associated answer. In addition, the the associated answer. In addition, the answerer MUST insert an SDP
answerer MUST insert an SDP 'setup' attribute with a value that does 'setup' attribute with a value that does not change the previously
not change the previously negotiated DTLS roles, and one or more SDP negotiated DTLS roles, and one or more SDP 'fingerprint' attributes
'fingerprint' attributes values that do not change the previously values that do not change the previously sent fingerprints, in the
sent fingerprints, in the answer. answer.
If the answerer receives an offer that does not contain an SDP 'dtls- If the answerer receives an offer that does not contain an SDP 'dtls-
association-id' attribute, the answerer MUST NOT insert a 'dtls- id' attribute, the answerer MUST NOT insert a 'dtls-id' attribute in
association-id' attribute in the answer. the answer.
If a new DTLS association is to be established, and if the answerer If a new DTLS association is to be established, and if the answerer
inserts an SDP 'setup' attribute with an 'active' value in the inserts an SDP 'setup' attribute with an 'active' value in the
answer, the answerer MUST initiate a DTLS handshake by sending a DTLS answer, the answerer MUST initiate a DTLS handshake by sending a DTLS
ClientHello message towards the offerer. ClientHello message towards the offerer.
5.4. Offerer Processing of the SDP Answer 5.4. Offerer Processing of the SDP Answer
When an offerer receives an answer that contains an SDP 'dtls- When an offerer receives an answer that contains an SDP 'dtls-id'
association-id' attribute with a new value, and if the offerer attribute with a new value, and if the offerer becomes DTLS client
becomes DTLS client (based on the value of the SDP 'setup' attribute (based on the value of the SDP 'setup' attribute value [RFC4145]),
value [RFC4145]), the offerer MUST establish a DTLS association. If the offerer MUST establish a DTLS association. If the offerer
the offerer becomes DTLS server, it MUST wait for the answerer to becomes DTLS server, it MUST wait for the answerer to establish the
establish the DTLS association. DTLS association.
If the answer contains an SDP 'dtls-association-id' attribute with a If the answer contains an SDP 'dtls-id' attribute with a previously
previously assigned value, the offerer will continue using the assigned value, the offerer will continue using the previously
previously established DTLS association. It is considered an error established DTLS association. It is considered an error case if the
case if the answer contains a 'dtls-association-id' attribute with a answer contains a 'dtls-id' attribute with a previously assigned
previously assigned value, and a DTLS association does not exist. value, and a DTLS association does not exist.
An offerer needs to be able to handle error conditions that can occur An offerer needs to be able to handle error conditions that can occur
during an offer/answer transaction, e.g. if an answer contains an SDP during an offer/answer transaction, e.g. if an answer contains an SDP
'dtls-association-id' attribute with a previosuly assigned value even 'dtls-id' attribute with a previosuly assigned value even if no DTLS
if no DTLS association exists, or if the answer contains one or more association exists, or if the answer contains one or more new
new fingerprint values for an existing DTLS association. If such fingerprint values for an existing DTLS association. If such error
error case occurs, the offerer SHOULD terminate the associated DTLS case occurs, the offerer SHOULD terminate the associated DTLS
association (if it exists) and send a new offer in order to terminate association (if it exists) and send a new offer in order to terminate
each media stream using the DTLS association, by setting the each media stream using the DTLS association, by setting the
associated port value to zero [RFC4145]. associated port value to zero [RFC4145].
5.5. Modifying the Session 5.5. Modifying the Session
When the offerer sends a subsequent offer, and if the offerer wants When the offerer sends a subsequent offer, and if the offerer wants
to establish a new DTLS association, the offerer MUST insert an SDP to establish a new DTLS association, the offerer MUST insert an SDP
'dtls-association-id' attribute with a new value in the offer. In 'dtls-id' attribute with a new value in the offer. In addition, the
addition, the offerer MUST insert an SDP 'setup' attribute according offerer MUST insert an SDP 'setup' attribute according to the
to the procedures in [RFC4145], and one or more SDP 'fingerprint' procedures in [RFC4145], and one or more SDP 'fingerprint' attributes
attributes according to the procedures in [RFC4572], in the offer. according to the procedures in [RFC4572], in the offer.
when the offerer sends a subsequent offer, and the offerer does not when the offerer sends a subsequent offer, and the offerer does not
want to establish a new DTLS association, and if a previously want to establish a new DTLS association, and if a previously
established DTLS association exists, the offerer MUST insert an SDP established DTLS association exists, the offerer MUST insert an SDP
'dtls-association-id' attribute with a previously assigned value in 'dtls-id' attribute with a previously assigned value in the offer.
the offer. In addition, the offerer MUST insert an SDP 'setup' In addition, the offerer MUST insert an SDP 'setup' attribute with a
attribute with a value that does not change the previously negotiated value that does not change the previously negotiated DTLS roles, and
DTLS roles, and one or more SDP 'fingerprint' attributes with values one or more SDP 'fingerprint' attributes with values that do not
that do not change the previously sent fingerprints, in the offer. change the previously sent fingerprints, in the offer.
NOTE: When a new DTLS association is established, each endpoint needs NOTE: When a new DTLS association is established, each endpoint needs
to be prepared to receive data on both the new and old DTLS to be prepared to receive data on both the new and old DTLS
associations as long as both are alive. associations as long as both are alive.
6. ICE Considerations 6. ICE Considerations
When ICE is used, the ICE connectivity checks are performed before When ICE is used, the ICE connectivity checks are performed before
the DTLS handshake begins. Note that if aggressive nomination mode the DTLS handshake begins. Note that if aggressive nomination mode
is used, multiple candidate pairs may be marked valid before ICE is used, multiple candidate pairs may be marked valid before ICE
finally converges on a single candidate pair. finally converges on a single candidate pair.
An ICE restart [RFC5245] does not by default require a new DTLS NOTE: Aggressive nomination has been deprecated from ICE, but must
still be supported for backwards compatibility reasons.
When new DTLS association is established over an unreliable
transport, in order to disambiguate any packets associated with newly
established DTLS association, at least one of the endpoints MUST
allocate a completely new set of ICE candidates which were not
recently used for any other DTLS association. This means that
answerer cannot initiate a new DTLS association unless the offerer
initiated ICE restart [RFC5245]. If the answerer wants to initiate a
new DTLS association, it needs to initiate an ICE restart on its own.
However, an ICE restart does not by default require a new DTLS
association to be established. association to be established.
NOTE: Simple Traversal of the UDP Protocol through NAT (STUN) packets
are sent directly over UDP, not over DTLS. [RFC3261] describes how
to demultiplex STUN packets from DTLS packets and SRTP packets.
As defined in [RFC5763], each ICE candidate associated with a As defined in [RFC5763], each ICE candidate associated with a
component is treated as being part of the same DTLS association. component is treated as being part of the same DTLS association.
Therefore, from a DTLS perspective it is not considered a change of Therefore, from a DTLS perspective it is not considered a change of
local transport parameters when an endpoint switches between those local transport parameters when an endpoint switches between those
ICE candidates. ICE candidates.
7. Transport Protocol Considerations 7. Transport Protocol Considerations
7.1. Transport Re-Usage 7.1. Transport Re-Usage
skipping to change at page 9, line 50 skipping to change at page 10, line 36
callees. This is referred to as forking. If forking occurs, callees. This is referred to as forking. If forking occurs,
separate DTLS associations MUST be established between the caller and separate DTLS associations MUST be established between the caller and
each callee. each callee.
It is possible to send an INVITE request which does not contain an It is possible to send an INVITE request which does not contain an
SDP offer. Such INVITE request is often referred to as an 'empty SDP offer. Such INVITE request is often referred to as an 'empty
INVITE', or an 'offer-less INVITE'. The receiving endpoint will INVITE', or an 'offer-less INVITE'. The receiving endpoint will
include the SDP offer in a response associated with the response. include the SDP offer in a response associated with the response.
When the endpoint generates such SDP offer, if a previously When the endpoint generates such SDP offer, if a previously
established DTLS association exists, the offerer SHOULD insert an SDP established DTLS association exists, the offerer SHOULD insert an SDP
'dtls-association-id' attribute, and one or more SDP 'fingerprint' 'dtls-id' attribute, and one or more SDP 'fingerprint' attributes,
attributes, with previously assigned attribute values. If a with previously assigned attribute values. If a previously
previously established DTLS association did not exists offer SHOULD established DTLS association did not exists offer SHOULD be generated
be generated based on the same rules as new offer Section 5.2. based on the same rules as new offer Section 5.2. Regardless of the
Regardless of the previous existence of DTLS association, the SDP previous existence of DTLS association, the SDP 'setup' attribute
'setup' attribute MUST be included according to rules defiend in MUST be included according to rules defiend in [RFC4145] and if ICE
[RFC4145] and if ICE is used, ICE restart MUST be initiated as is used, ICE restart MUST be initiated as defined in [RFC5763].
defined in [RFC5763].
9. RFC Updates 9. RFC Updates
9.1. General 9.1. General
This section updates specifications that use DTLS-protected media, in This section updates specifications that use DTLS-protected media, in
order to reflect the procedures defined in this specification. order to reflect the procedures defined in this specification.
9.2. Update to RFC 5763 9.2. Update to RFC 5763
skipping to change at page 18, line 30 skipping to change at page 19, line 17
5.2.1. ICE Usage 5.2.1. ICE Usage
The Interactive Connectivity Establishment (ICE) [RFC5245] The Interactive Connectivity Establishment (ICE) [RFC5245]
considerations for DTLS-protected media are described in considerations for DTLS-protected media are described in
[RFCXXXX]. [RFCXXXX].
10. Security Considerations 10. Security Considerations
This specification does not modify the security considerations This specification does not modify the security considerations
associated with DTLS, or the SDP offer/answer mechanism. In addition associated with DTLS, or the SDP offer/answer mechanism. In addition
to the introduction of the SDP 'dtls-association-id' attribute, the to the introduction of the SDP 'dtls-id' attribute, the specification
specification simply clarifies the procedures for negotiating and simply clarifies the procedures for negotiating and establishing a
establishing a DTLS association. DTLS association.
11. IANA Considerations 11. IANA Considerations
This document updates the "Session Description Protocol Parameters" This document updates the "Session Description Protocol Parameters"
registry as specified in Section 8.2.2 of [RFC4566]. Specifically, registry as specified in Section 8.2.2 of [RFC4566]. Specifically,
it adds the SDP dtls-association-id attribute to the table for SDP it adds the SDP dtls-id attribute to the table for SDP media level
media level attributes. attributes.
Attribute name: dtls-association-id Attribute name: dtls-id
Type of attribute: media-level Type of attribute: media-level
Subject to charset: no Subject to charset: no
Purpose: Indicate whether a new DTLS association is to be established/re-established. Purpose: Indicate whether a new DTLS association is to be
Appropriate Values: see Section 4 established/re-established.
Contact name: Christer Holmberg Appropriate Values: see Section 4
Category: IDENTICAL Contact name: Christer Holmberg
Category: IDENTICAL
12. Acknowledgements 12. Acknowledgements
Thanks to Justin Uberti, Martin Thomson, Paul Kyzivat, Jens Guballa, Thanks to Justin Uberti, Martin Thomson, Paul Kyzivat, Jens Guballa,
Charles Eckel and Gonzalo Salgueiro for providing comments and Charles Eckel and Gonzalo Salgueiro for providing comments and
suggestions on the draft. suggestions on the draft.
13. Change Log 13. Change Log
[RFC EDITOR NOTE: Please remove this section when publishing] [RFC EDITOR NOTE: Please remove this section when publishing]
Changes from draft-ietf-mmusic-sdp-dtls-11
o Attribute name changed to dtls-id
o Additional text based on comments from Roman Shpount.
Changes from draft-ietf-mmusic-sdp-dtls-10 Changes from draft-ietf-mmusic-sdp-dtls-10
o Modified document to use dtls-association-id instead of dtls- o Modified document to use dtls-id instead of dtls-connection
connection
o Changes are based on comments from Eric Rescorla, Justin Uberti, o Changes are based on comments from Eric Rescorla, Justin Uberti,
and Paul Kyzivat. and Paul Kyzivat.
Changes from draft-ietf-mmusic-sdp-dtls-08 Changes from draft-ietf-mmusic-sdp-dtls-08
o Offer/Answer section modified in order to allow sending of o Offer/Answer section modified in order to allow sending of
multiple SDP 'fingerprint' attributes. multiple SDP 'fingerprint' attributes.
o Terminology made consistent: 'DTLS connection' replaced with 'DTLS o Terminology made consistent: 'DTLS connection' replaced with 'DTLS
skipping to change at page 19, line 50 skipping to change at page 20, line 40
multiple transports added. multiple transports added.
o Mux category added to IANA Considerations. o Mux category added to IANA Considerations.
o Normative text regarding mux category and source-specific o Normative text regarding mux category and source-specific
applicability added. applicability added.
o Reference to RFC 7315 added. o Reference to RFC 7315 added.
o Clarified that offerer/answerer that has not been updated to o Clarified that offerer/answerer that has not been updated to
support this specification will not include the dtls-association- support this specification will not include the dtls-id attribute
id attribute in offers and answers. in offers and answers.
o Editorial corrections based on WGLC comments from Charles Eckel. o Editorial corrections based on WGLC comments from Charles Eckel.
Changes from draft-ietf-mmusic-sdp-dtls-05 Changes from draft-ietf-mmusic-sdp-dtls-05
o Text on handling offer/answer error conditions added. o Text on handling offer/answer error conditions added.
Changes from draft-ietf-mmusic-sdp-dtls-04 Changes from draft-ietf-mmusic-sdp-dtls-04
o Editorial nits fixed based on comments from Paul Kyzivat: o Editorial nits fixed based on comments from Paul Kyzivat:
Changes from draft-ietf-mmusic-sdp-dtls-03 Changes from draft-ietf-mmusic-sdp-dtls-03
o Changes based on comments from Paul Kyzivat: o Changes based on comments from Paul Kyzivat:
o - Modification of dtls-association-id attribute section. o - Modification of dtls-id attribute section.
o - Removal of IANA considerations subsection. o - Removal of IANA considerations subsection.
o - Making note into normative text in o/a section. o - Making note into normative text in o/a section.
o Changes based on comments from Martin Thompson: o Changes based on comments from Martin Thompson:
o - Abbreviations section removed. o - Abbreviations section removed.
o - Clarify that a new DTLS association requires a new o/a o - Clarify that a new DTLS association requires a new o/a
transaction. transaction.
Changes from draft-ietf-mmusic-sdp-dtls-02 Changes from draft-ietf-mmusic-sdp-dtls-02
o - Updated RFCs added to boilerplate. o - Updated RFCs added to boilerplate.
Changes from draft-ietf-mmusic-sdp-dtls-01 Changes from draft-ietf-mmusic-sdp-dtls-01
o - Annex regarding 'dtls-association-id-id' attribute removed. o - Annex regarding 'dtls-id-id' attribute removed.
o - Additional SDP offer/answer procedures, related to certificates, o - Additional SDP offer/answer procedures, related to certificates,
added. added.
o - Updates to RFC 5763 and RFC 7345 added. o - Updates to RFC 5763 and RFC 7345 added.
o - Transport protocol considerations added. o - Transport protocol considerations added.
Changes from draft-ietf-mmusic-sdp-dtls-00 Changes from draft-ietf-mmusic-sdp-dtls-00
o - SDP 'connection' attribute replaced with new 'dtls-association- o - SDP 'connection' attribute replaced with new 'dtls-id'
id' attribute. attribute.
o - IANA Considerations added. o - IANA Considerations added.
o - E-mail regarding 'dtls-association-id-id' attribute added as o - E-mail regarding 'dtls-id-id' attribute added as Annex.
Annex.
Changes from draft-holmberg-mmusic-sdp-dtls-01 Changes from draft-holmberg-mmusic-sdp-dtls-01
o - draft-ietf-mmusic version of draft submitted. o - draft-ietf-mmusic version of draft submitted.
o - Draft file name change (sdp-dtls -> dtls-sdp) due to collision o - Draft file name change (sdp-dtls -> dtls-sdp) due to collision
with another expired draft. with another expired draft.
o - Clarify that if ufrag in offer is unchanged, it must be o - Clarify that if ufrag in offer is unchanged, it must be
unchanged in associated answer. unchanged in associated answer.
skipping to change at page 22, line 15 skipping to change at page 23, line 5
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, DOI 10.17487/RFC4566, Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
July 2006, <http://www.rfc-editor.org/info/rfc4566>. July 2006, <http://www.rfc-editor.org/info/rfc4566>.
[RFC4572] Lennox, J., "Connection-Oriented Media Transport over the [RFC4572] Lennox, J., "Connection-Oriented Media Transport over the
Transport Layer Security (TLS) Protocol in the Session Transport Layer Security (TLS) Protocol in the Session
Description Protocol (SDP)", RFC 4572, Description Protocol (SDP)", RFC 4572,
DOI 10.17487/RFC4572, July 2006, DOI 10.17487/RFC4572, July 2006,
<http://www.rfc-editor.org/info/rfc4572>. <http://www.rfc-editor.org/info/rfc4572>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<http://www.rfc-editor.org/info/rfc5234>.
[RFC5245] Rosenberg, J., "Interactive Connectivity Establishment [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
(ICE): A Protocol for Network Address Translator (NAT) (ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols", RFC 5245, Traversal for Offer/Answer Protocols", RFC 5245,
DOI 10.17487/RFC5245, April 2010, DOI 10.17487/RFC5245, April 2010,
<http://www.rfc-editor.org/info/rfc5245>. <http://www.rfc-editor.org/info/rfc5245>.
[RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework [RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework
for Establishing a Secure Real-time Transport Protocol for Establishing a Secure Real-time Transport Protocol
(SRTP) Security Context Using Datagram Transport Layer (SRTP) Security Context Using Datagram Transport Layer
Security (DTLS)", RFC 5763, DOI 10.17487/RFC5763, May Security (DTLS)", RFC 5763, DOI 10.17487/RFC5763, May
skipping to change at page 23, line 14 skipping to change at page 23, line 44
[I-D.ietf-mmusic-sdp-mux-attributes] [I-D.ietf-mmusic-sdp-mux-attributes]
Nandakumar, S., "A Framework for SDP Attributes when Nandakumar, S., "A Framework for SDP Attributes when
Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-12 Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-12
(work in progress), January 2016. (work in progress), January 2016.
[I-D.ietf-mmusic-sdp-bundle-negotiation] [I-D.ietf-mmusic-sdp-bundle-negotiation]
Holmberg, C., Alvestrand, H., and C. Jennings, Holmberg, C., Alvestrand, H., and C. Jennings,
"Negotiating Media Multiplexing Using the Session "Negotiating Media Multiplexing Using the Session
Description Protocol (SDP)", draft-ietf-mmusic-sdp-bundle- Description Protocol (SDP)", draft-ietf-mmusic-sdp-bundle-
negotiation-25 (work in progress), January 2016. negotiation-29 (work in progress), April 2016.
Authors' Addresses Authors' Addresses
Christer Holmberg Christer Holmberg
Ericsson Ericsson
Hirsalantie 11 Hirsalantie 11
Jorvas 02420 Jorvas 02420
Finland Finland
Email: christer.holmberg@ericsson.com Email: christer.holmberg@ericsson.com
Roman Shpount Roman Shpount
TurboBridge TurboBridge
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