draft-ietf-mmusic-dtls-sdp-10.txt   draft-ietf-mmusic-dtls-sdp-11.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 4, 2016 March 3, 2016 Expires: September 22, 2016 March 21, 2016
Using the SDP Offer/Answer Mechanism for DTLS Using the SDP Offer/Answer Mechanism for DTLS
draft-ietf-mmusic-dtls-sdp-10.txt draft-ietf-mmusic-dtls-sdp-11.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-
connection'. 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 4, 2016. This Internet-Draft will expire on September 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 13 skipping to change at page 2, line 13
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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 . . . . . . . . . . 3 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-connection Attribute . . . . . . . . . . . . . . . . 4 4. SDP dtls-association-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 . . . . . . . . . . . . 6 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 . . . . . . . . . . 7 5.4. Offerer Processing of the SDP Answer . . . . . . . . . . 8
5.5. Modifying the Session . . . . . . . . . . . . . . . . . . 8 5.5. Modifying the Session . . . . . . . . . . . . . . . . . . 8
6. ICE Considerations . . . . . . . . . . . . . . . . . . . . . 8 6. ICE Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Transport Protocol Considerations . . . . . . . . . . . . . . 9 7. Transport Protocol Considerations . . . . . . . . . . . . . . 9
7.1. Transport Re-Usage . . . . . . . . . . . . . . . . . . . 9 7.1. Transport Re-Usage . . . . . . . . . . . . . . . . . . . 9
8. SIP Considerations . . . . . . . . . . . . . . . . . . . . . 9 8. SIP Considerations . . . . . . . . . . . . . . . . . . . . . 9
9. RFC Updates . . . . . . . . . . . . . . . . . . . . . . . . . 9 9. RFC Updates . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 9 9.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.2. Update to RFC 5763 . . . . . . . . . . . . . . . . . . . 9 9.2. Update to RFC 5763 . . . . . . . . . . . . . . . . . . . 10
9.3. Update to RFC 7345 . . . . . . . . . . . . . . . . . . . 15 9.3. Update to RFC 7345 . . . . . . . . . . . . . . . . . . . 15
10. Security Considerations . . . . . . . . . . . . . . . . . . . 18 10. Security Considerations . . . . . . . . . . . . . . . . . . . 18
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19
13. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 18 13. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 19
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 21
14.1. Normative References . . . . . . . . . . . . . . . . . . 21 14.1. Normative References . . . . . . . . . . . . . . . . . . 21
14.2. Informative References . . . . . . . . . . . . . . . . . 22 14.2. Informative References . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22 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
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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-
connection'. The attribute is used in SDP offers and answers to association-id'. The attribute contains a unique value associated
explicitly indicate whether a new DTLS association is to be with a DTLS association, and by providing a new value in SDP offers
established/re-established. The attribute can be used both with and and answers the attribute can be used to indicate whether a new DTLS
without ICE. association 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
A new DTLS association MUST be established in the following cases: A new DTLS association MUST be established in the following cases:
o The DTLS roles change; o The DTLS roles change;
o A fingerprint (certificate) value changes; or o One or more fingerprint values are modified, added or removed; or
o The intent to establish of a new DTLS association is explicitly o The intent to establish a new DTLS association is explicitly
signaled; signaled;
NOTE: The first two items list above are based on the procedures in NOTE: The first two items list above are based on the procedures in
[RFC5763]. This draft adds the support for explicit signaling. [RFC5763]. This specification adds the support for explicit
signaling.
Whenever an entity determines, based on the criteria above, that a Whenever an entity determines, based on the criteria above, that a
new DTLS association is required, the entity MUST initiate an new DTLS association is required, the entity MUST initiate an
associated SDP offer/answer transaction, following the procedures in associated SDP offer/answer transaction, following the procedures in
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-connection' attribute with a 'new' value and/or use the SDP 'dtls-association-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, the SDP 'dtls-connection' attribute MUST to span multiple transports, and if the transport is changed, a new
be set to 'new' if the transport is changed. An example of such case value MUST be assigned to the the SDP 'dtls-association-id'
is when DTLS is carried over SCTP, as described in [RFC6083]. attribute. An example of such case is when DTLS is carried over
SCTP, as described 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 use the SDP either change its DTLS role, a fingerprint value and/or assign a new
'dtls-connection' attribute with a 'new' value Section 4. value to the SDP 'dtls-association-id' attribute Section 4.
4. SDP dtls-connection Attribute 4. SDP dtls-association-id Attribute
The SDP 'connection' attribute [RFC4145] was originally defined for The SDP 'dtls-association-id' attribute contains a unique value
connection-oriented protocols, e.g. TCP and TLS. This section associated with a DTLS association.
defines a similar attribute, 'dtls-connection', to be used with DTLS.
Name: dtls-connection Name: dtls-association-id
Value: conn-value Value: conn-value
Usage Level: media Usage Level: media
Charset Dependent: no Charset Dependent: no
Syntax: Syntax:
conn-value = "new" / "existing" conn-value = 1*256alphanum
Example: Example:
a=dtls-connection:existing a=dtls-association-id:abc3dl
A 'dtls-connection' attribute value of 'new' indicates that a new A 'dtls-association-id' attribute that contains a new value indicates
DTLS association MUST be established. A 'dtls-connection' attribute an intention to establish a new DTLS association. A 'dtls-
value of 'existing' indicates an intention to reuse an existing association-id' attribute that contains a previously assigned value
association. indicates an intention to reuse an existing association.
Unlike the SDP 'connection' attribute for TLS, there is no default There is no default value defined for the SDP 'dtls-association-id'
value defined for the 'dtls-connection' attribute. Implementations attribute. Implementations that wish to use the attribute MUST
that wish to use the attribute MUST explicitly include it in SDP explicitly include it in SDP offers and answers. If an offer or
offers and answers. If an offer or answer does not contain an answer does not contain an attribute (this could happen if the
attribute (this could happen if the offerer or answerer represents an offerer or answerer represents an existing implementation that has
existing implementation that has not been updated to support the not been updated to support the attribute defined in this
attribute defined in this specification), other means needs to be specification or an implementation which allocates a new temporary
used in order for endpoints to determine whether an offer or answer certificate for each association and uses change in fingerprint to
is associated with an event that requires the DTLS association to be indicate new association), other means needs to be used in order for
re-established. endpoints to determine whether an offer or answer is associated with
an event that 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-
connection' attribute is 'IDENTICAL', which means that the attribute association-id' attribute is 'IDENTICAL', which means that the
value must be identical across all media descriptions being attribute value must be identical across all media descriptions being
multiplexed [I-D.ietf-mmusic-sdp-bundle-negotiation]. multiplexed [I-D.ietf-mmusic-sdp-bundle-negotiation].
For RTP-based media, the 'dtls-connection' attribute apply to whole For RTP-based media, the 'dtls-association-id' attribute apply to
associated media description. The attribute MUST NOT be defined per whole associated media description. The attribute MUST NOT be
source (using the SDP 'ssrc' attribute [RFC5576]). defined per 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-connection' attribute. That document is of usage of the SDP 'dtls-association-id' attribute. That document
herein revised to make use of these new procedures. is herein 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 stream.
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-connection' attribute, defined in this o The SDP 'dtls-association-id' attribute, defined in this
specification, is used to explicitly indicate whether a new DTLS specification, indicates a unique value associated with the DTLS
association is to be established or a previous association is to association. The attribute value can be used to explicitly
be used. indicate the 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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fingerprint value associated with the DTLS association. The use of fingerprint value associated with the DTLS association. The use of
SHA-256 is preferred. SHA-256 is preferred.
Endpoints MUST, at a minimum, support Endpoints MUST, at a minimum, support
TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 and MUST support TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 and MUST support
TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256. UDPTL over DTLS MUST prefer TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256. UDPTL over DTLS MUST prefer
TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 and any other Perfect Forward TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 and any other Perfect Forward
Secrecy (PFS) cipher suites over non-PFS cipher suites. Secrecy (PFS) cipher suites over non-PFS cipher suites.
Implementations SHOULD disable TLS-level compression. Implementations SHOULD disable TLS-level compression.
The certificate received during the DTLS handshake MUST match a The certificate received during the DTLS handshake MUST match at
fingerprint received in an SDP "fingerprint" attribute. If a least one of the certificate fingerprints received in SDP
fingerprint does not match the hashed certificate, then the endpoint 'fingerprint' attributes. If no fingerprint matches the hashed
MUST tear down the media session immediately. Note that it is certificate, then an endpoint MUST tear down the media session
permissible to wait until the other side's fingerprint has been immediately. Note that it is permissible to wait until the other
received before establishing the connection; however, this may have side's fingerprint has been received before establishing the
undesirable latency effects. connection; however, this may have undesirable latency effects.
SDP offerers and answerers might reuse certificates across multiple
DTLS associations, and provide identical fingerprint values for each
DTLS association. It MUST be ensured that the combination of the
fingerprint values and the SDP 'dtls-association-id' attribute value
is unique across all DTLS associations.
If an SDP offerer or answerer generates a new temporary self-signed
certificate for each new DTLS association, they can omit the SDP
'dtls-association-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-connection' establish a DTLS association, it MUST insert an SDP 'dtls-
attribute with a 'new' value in the offer. In addition, the offerer association-id' attribute with a new value in the offer. In
MUST insert an SDP 'setup' attribute according to the procedures in addition, the offerer MUST insert an SDP 'setup' attribute according
[RFC4145], and one or more SDP 'fingerprint' attributes according to to the procedures in [RFC4145], and one or more SDP 'fingerprint'
the procedures in [RFC4572], in the offer. attributes according to 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-
connection' attribute with a 'new' value, or if the answerer receives association-id' attribute with a new value, or if the answerer
an offer that contains an 'dtls-connection' attribute with an receives an offer that contains an 'dtls-association-id' attribute
'existing' value and the answerer determines (based on the criteria with a previously assigned value and the answerer determines (based
for establishing a new DTLS association) that a new DTLS association on the criteria for establishing a new DTLS association) that a new
is to be established, the answerer MUST insert a 'new' value in the DTLS association is to be established, the answerer MUST insert a new
associated answer. In addition, the answerer MUST insert an SDP value in the associated answer. In addition, the answerer MUST
'setup' attribute according to the procedures in [RFC4145], and one insert an SDP 'setup' attribute according to the procedures in
or more SDP 'fingerprint' attributes according to the procedures in [RFC4145], and one or more SDP 'fingerprint' attributes according to
[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-
connection' attribute with a 'new' value, and if the answerer does association-id' attribute with a new value, and if the answerer does
not accept the establishment of a new DTLS association, the answerer not accept the establishment of a new DTLS association, the answerer
MUST reject the "m=" lines associated with the suggested DTLS MUST reject the "m=" lines associated with the suggested DTLS
association [RFC3264]. association [RFC3264].
If an answerer receives an offer that contains a 'dtls-connection' If an answerer receives an offer that contains a 'dtls-association-
attribute with an 'existing' value, and if the answerer determines id' attribute with a previously assigned value, and if the answerer
that a new DTLS association is not to be established, the answerer determines that a new DTLS association is not to be established, the
MUST insert a 'dtls-connection' attribute with an 'existing' value in answerer MUST insert a 'dtls-association-id' attribute with the
the associated answer. In addition, the answerer MUST insert an SDP previously assigned value in the associated answer. In addition, the
'setup' attribute with a value that does not change the previously answerer MUST insert an SDP 'setup' attribute with a value that does
negotiated DTLS roles, and one or more SDP 'fingerprint' attributes not change the previously negotiated DTLS roles, and one or more SDP
values that do not change the previously sent fingerprints, in the 'fingerprint' attributes values that do not change the previously
answer. sent fingerprints, in the 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-
connection' attribute, the answerer MUST NOT insert a 'dtls- association-id' attribute, the answerer MUST NOT insert a 'dtls-
connection' attribute in the answer. association-id' attribute in 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-
connection' attribute with a 'new' value, and if the offerer becomes association-id' attribute with a new value, and if the offerer
DTLS client (based on the value of the SDP 'setup' attribute value becomes DTLS client (based on the value of the SDP 'setup' attribute
[RFC4145]), the offerer MUST establish a DTLS association. If the value [RFC4145]), the offerer MUST establish a DTLS association. If
offerer becomes DTLS server, it MUST wait for the answerer to the offerer becomes DTLS server, it MUST wait for the answerer to
establish the DTLS association. establish the DTLS association.
If the answer contains an SDP 'dtls-connection' attribute with an If the answer contains an SDP 'dtls-association-id' attribute with a
'existing' value, the offerer will continue using the previously previously assigned value, the offerer will continue using the
established DTLS association. It is considered an error case if the previously established DTLS association. It is considered an error
answer contains a 'dtls-connection' attribute with an 'existing' case if the answer contains a 'dtls-association-id' attribute with a
value, and a DTLS association does not exist. previously assigned 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-connection' attribute with an 'existing' value even if no DTLS 'dtls-association-id' attribute with a previosuly assigned value even
association exists, or if the answer contains one or more new if no DTLS association exists, or if the answer contains one or more
fingerprint values for an existing DTLS association. If such error new fingerprint values for an existing DTLS association. If such
case occurs, the offerer SHOULD terminate the associated DTLS error 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-connection' attribute with a 'new' value in the offer. In 'dtls-association-id' attribute with a new value in the offer. In
addition, the offerer MUST insert an SDP 'setup' attribute according addition, the offerer MUST insert an SDP 'setup' attribute according
to the procedures in [RFC4145], and one or more SDP 'fingerprint' to the procedures in [RFC4145], and one or more SDP 'fingerprint'
attributes according to the procedures in [RFC4572], in the offer. attributes 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-connection' attribute with an 'existing' value in the offer. 'dtls-association-id' attribute with a previously assigned value in
In addition, the offerer MUST insert an SDP 'setup' attribute with a the offer. In addition, the offerer MUST insert an SDP 'setup'
value that does not change the previously negotiated DTLS roles, and attribute with a value that does not change the previously negotiated
one or more SDP 'fingerprint' attributes with values that do not DTLS roles, and one or more SDP 'fingerprint' attributes with values
change the previously sent fingerprints, in the offer. that do not 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
skipping to change at page 9, line 32 skipping to change at page 9, line 46
When the Session Initiation Protocol (SIP) [RFC3261] is used as the When the Session Initiation Protocol (SIP) [RFC3261] is used as the
signal protocol for establishing a multimedia session, dialogs signal protocol for establishing a multimedia session, dialogs
[RFC3261] might be established between the caller and multiple [RFC3261] might be established between the caller and multiple
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 'offerless 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, it MUST assign an SDP When the endpoint generates such SDP offer, if a previously
'dtls-connection' attribute, with a 'new' value, to each 'm-' line established DTLS association exists, the offerer SHOULD insert an SDP
that describes DTLS protected media. If ICE is used, the endpoint 'dtls-association-id' attribute, and one or more SDP 'fingerprint'
MUST allocate a new set of ICE candidates, in order to ensure that attributes, with previously assigned attribute values. If a
two DTLS association would not be running over the same transport. previously established DTLS association did not exists offer SHOULD
be generated based on the same rules as new offer Section 5.2.
Regardless of the previous existence of DTLS association, the SDP
'setup' attribute MUST be included according to rules defiend in
[RFC4145] and if ICE is used, ICE restart MUST be initiated as
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 15 skipping to change at page 18, line 30
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-connection' attribute, the to the introduction of the SDP 'dtls-association-id' attribute, the
specification simply clarifies the procedures for negotiating and specification simply clarifies the procedures for negotiating and
establishing a DTLS association. establishing a 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-connection attribute to the table for SDP media it adds the SDP dtls-association-id attribute to the table for SDP
level attributes. media level attributes.
Attribute name: dtls-connection Attribute name: dtls-association-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 established/re-established.
Appropriate Values: see Section 4 Appropriate Values: see Section 4
Contact name: Christer Holmberg Contact name: Christer Holmberg
Category: IDENTICAL 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-10
o Modified document to use dtls-association-id instead of dtls-
connection
o Changes are based on comments from Eric Rescorla, Justin Uberti,
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
association'. association'.
o Editorial changes based on comments from Paul Kyzivat. o Editorial changes based on comments from Paul Kyzivat.
skipping to change at page 19, line 27 skipping to change at page 19, line 50
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-connection support this specification will not include the dtls-association-
attribute in offers and answers. id attribute 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-connection attribute section. o - Modification of dtls-association-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-connection-id' attribute removed. o - Annex regarding 'dtls-association-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-connection' o - SDP 'connection' attribute replaced with new 'dtls-association-
attribute. id' attribute.
o - IANA Considerations added. o - IANA Considerations added.
o - E-mail regarding 'dtls-connection-id' attribute added as Annex. o - E-mail regarding 'dtls-association-id-id' attribute added as
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.
 End of changes. 52 change blocks. 
129 lines changed or deleted 155 lines changed or added

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