draft-ietf-mmusic-dtls-sdp-03.txt   draft-ietf-mmusic-dtls-sdp-04.txt 
Network Working Group C. Holmberg Network Working Group C. Holmberg
Internet-Draft Ericsson Internet-Draft Ericsson
Updates: 5763,7315 (if approved) R. Shpount Updates: 5763,7315 (if approved) R. Shpount
Intended status: Standards Track TurboBridge Intended status: Standards Track TurboBridge
Expires: June 10, 2016 December 8, 2015 Expires: July 21, 2016 January 18, 2016
Using the SDP Offer/Answer Mechanism for DTLS Using the SDP Offer/Answer Mechanism for DTLS
draft-ietf-mmusic-dtls-sdp-03.txt draft-ietf-mmusic-dtls-sdp-04.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'. connection'.
skipping to change at page 1, line 36 skipping to change at page 1, line 36
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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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 June 10, 2016. This Internet-Draft will expire on July 21, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 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.
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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. Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Establishing a new DTLS Association . . . . . . . . . . . . . 3
4. Establishing a new DTLS Association . . . . . . . . . . . . . 3 3.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 3
4.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.2. Change of Local Transport Parameters . . . . . . . . . . 3
4.2. Change of Local Transport Parameters . . . . . . . . . . 4 3.3. Change of ICE ufrag value . . . . . . . . . . . . . . . . 4
4.3. Change of ICE ufrag value . . . . . . . . . . . . . . . . 4 3.4. Multiple SDP fingerprint attributes . . . . . . . . . . . 4
4.4. Multiple SDP fingerprint attributes . . . . . . . . . . . 4 4. SDP dtls-connection Attribute . . . . . . . . . . . . . . . . 4
5. SDP dtls-connection Attribute . . . . . . . . . . . . . . . . 4 5. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 5
5.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 4 5.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.2. ABNF . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5.2. Generating the Initial SDP Offer . . . . . . . . . . . . 6
6. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 5 5.3. Generating the Answer . . . . . . . . . . . . . . . . . . 6
6.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 5 5.4. Offerer Processing of the SDP Answer . . . . . . . . . . 7
6.2. Generating the Initial SDP Offer . . . . . . . . . . . . 6 5.5. Modifying the Session . . . . . . . . . . . . . . . . . . 7
6.3. Generating the Answer . . . . . . . . . . . . . . . . . . 6 6. ICE Considerations . . . . . . . . . . . . . . . . . . . . . 8
6.4. Offerer Processing of the SDP Answer . . . . . . . . . . 7 7. Transport Protocol Considerations . . . . . . . . . . . . . . 8
6.5. Modifying the Session . . . . . . . . . . . . . . . . . . 7 7.1. Transport Re-Usage . . . . . . . . . . . . . . . . . . . 8
7. ICE Considerations . . . . . . . . . . . . . . . . . . . . . 8 8. SIP Considerations . . . . . . . . . . . . . . . . . . . . . 8
8. Transport Protocol Considerations . . . . . . . . . . . . . . 8 9. RFC Updates . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Transport Re-Usage . . . . . . . . . . . . . . . . . . . 8 9.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 9
9. SIP Considerations . . . . . . . . . . . . . . . . . . . . . 8 9.2. Update to RFC 5763 . . . . . . . . . . . . . . . . . . . 9
10. RFC Updates . . . . . . . . . . . . . . . . . . . . . . . . . 9 9.3. Update to RFC 7345 . . . . . . . . . . . . . . . . . . . 14
10.1. General . . . . . . . . . . . . . . . . . . . . . . . . 9 10. Security Considerations . . . . . . . . . . . . . . . . . . . 17
10.2. Update to RFC 5763 . . . . . . . . . . . . . . . . . . . 9 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
10.3. Update to RFC 7345 . . . . . . . . . . . . . . . . . . . 14 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18
11. Security Considerations . . . . . . . . . . . . . . . . . . . 17 13. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 18
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 14. Normative References . . . . . . . . . . . . . . . . . . . . 19
12.1. Registration of New SDP Attribute . . . . . . . . . . . 17
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18
14. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 18
15. Normative References . . . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction 1. Introduction
[RFC5763] defines SDP Offer/Answer procedures for SRTP-DTLS. This [RFC5763] defines SDP Offer/Answer procedures for SRTP-DTLS. This
draft defines the SDP Offer/Answer [RFC3264] procedures for draft defines the SDP Offer/Answer [RFC3264] procedures for
negotiation DTLS in general, based on the procedures in [RFC5763]. negotiation DTLS in general, based on the procedures in [RFC5763].
This draft also defines a new SDP attribute, 'dtls-connection'. The This draft also defines a new SDP attribute, 'dtls-connection'. The
attribute is used in SDP offers and answers to explicitly indicate attribute is used in SDP offers and answers to explicitly indicate
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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 connection'. The attribute is used in SDP offers and answers to
explicitly indicate whether a new DTLS association is to be explicitly indicate whether a new DTLS association is to be
established/re-established. The attribute can be used both with and established/re-established. The attribute can be used both with and
without ICE. without ICE.
2. Abbreviations 2. Conventions
TBD
3. 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].
4. Establishing a new DTLS Association 3. Establishing a new DTLS Association
4.1. 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 The fingerprint (certificate) value changes; or o The fingerprint (certificate) value changes; or
o The establishment of a new DTLS association is explicitly o The establishment of 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 draft adds the support for explicit signaling.
Whenever an entity determines, based on the criteria above, that a
new DTLS association is the entity MUST initiate an associated SDP
offer/answer transaction, following to the procedures in 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.
4.2. Change of Local Transport Parameters 3.2. Change of Local Transport Parameters
If an endpoint modifies its local transport parameters (IP address If an endpoint modifies its local transport parameters (IP address
and/or port), and if the modification requires a new DTLS and/or port), and if the modification requires a new DTLS
association, the endpoint MUST either change its DTLS role, its association, the endpoint MUST either change its DTLS role, its
fingerprint value and/or use the SDP 'dtls-connection' attribute with fingerprint value and/or use the SDP 'dtls-connection' attribute with
a 'new' value Section 5. a 'new' value Section 4.
4.3. 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, its fingerprint value and/or use the SDP either change its DTLS role, its fingerprint value and/or use the SDP
'dtls-connection' attribute with a 'new' value Section 5. 'dtls-connection' attribute with a 'new' value Section 4.
4.4. Multiple SDP fingerprint attributes 3.4. Multiple SDP fingerprint attributes
It is possible to associate multiple SDP fingerprint attribute values It is possible to associate multiple SDP fingerprint attribute values
to an 'm-' line. If any of the attribute values associated with an to an 'm-' line. If any of the attribute values associated with an
'm-' line are removed, or if any new attribute values are added, it 'm-' line are removed, or if any new attribute values are added, it
is considered a fingerprint value change. is considered a fingerprint value change.
5. SDP dtls-connection Attribute 4. SDP dtls-connection Attribute
5.1. General
The SDP 'connection' attribute [RFC4145] was originally defined for The SDP 'connection' attribute [RFC4145] was originally defined for
connection-oriented protocols, e.g. TCP and TLS. This section connection-oriented protocols, e.g. TCP and TLS. This section
defines a similar attribute, 'dtls-connection', to be used with DTLS. defines a similar attribute, 'dtls-connection', to be used with DTLS.
Name: dtls-connection
Value: conn-value
Usage Level: media
Charset Dependent: no
Syntax:
conn-value = "new" / "existing"
Example:
a=dtls-connection:existing
A 'dtls-connection' attribute value of 'new' indicates that a new A 'dtls-connection' attribute value of 'new' indicates that a new
DTLS association MUST be established. A 'dtls-connection' attribute DTLS association MUST be established. A 'dtls-connection' attribute
value of 'existing' indicates that a new DTLS association MUST NOT be value of 'existing' indicates that a new DTLS association MUST NOT be
established. established.
Unlike the SDP 'connection' attribute for TLS, there is no default Unlike the SDP 'connection' attribute for TLS, there is no default
value defined for the 'dtls-connection' attribute. Implementations value defined for the 'dtls-connection' attribute. Implementations
that wish to use the attribute MUST explicitly include it in SDP that wish to use the attribute MUST explicitly include it in SDP
offers and answers. If an offer or answer does not contain an offers and answers. If an offer or answer does not contain an
attribute, other means needs to be used in order for endpoints to attribute, other means needs to be used in order for endpoints to
determine whether an offer or answer is associated with an event that determine whether an offer or answer is associated with an event that
requires the DTLS association to be re-established. requires the DTLS association to be re-established.
The SDP Offer/Answer [RFC3264] procedures associated with the The SDP Offer/Answer [RFC3264] procedures associated with the
attribute are defined in Section 6 attribute are defined in Section 5
5.2. ABNF
The ABNF [RFC5234] grammar for the SDP 'dtls-connection' attributes
is:
dtls-connection-attr = "a=dtls-connection:" conn-value
conn-value = "new" / "existing"
6. SDP Offer/Answer Procedures 5. SDP Offer/Answer Procedures
6.1. 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 usage specific SDP attributes etc) for individual regarding usage of usage specific SDP attributes etc) for individual
DTLS usages (e.g. SRTP-DTLS) are outside the scope of this DTLS usages (e.g. SRTP-DTLS) are outside the scope of this
specification, and needs to be specified in a usage specific specification, and needs to be specified in a usage specific
specification. specification.
NOTE: The procedures in this section are based on the procedures for NOTE: The procedures in this section are generalizations of
SRTP-DTLS [RFC5763], with the addition of usage of the SDP 'dtls- procedures first specified in SRTP-DTLS [RFC5763], with the addition
connection' attribute. of usage of the SDP 'dtls-connection' attribute. That document 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;
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provide the fingerprint value; and provide the fingerprint value; and
o The SDP 'dtls-connection' attribute, defined in this o The SDP 'dtls-connection' attribute, defined in this
specification, is used to explicitly indicate whether a new DTLS specification, is used to explicitly indicate whether a new DTLS
association is to be established or whether a previous association association is to be established or whether a previous association
is to be used. is to be used.
Endpoints MUST NOT use the SDP 'connection' attribute [RFC4145] when Endpoints MUST NOT use the SDP 'connection' attribute [RFC4145] when
negotiating a DTLS association. negotiating a DTLS association.
NOTE: The SDP 'connection' attribute may be used if the usage is The SDP 'connection' attribute MAY be used if the usage is associated
associated with another protocol layer, e.g. SCTP or TCP, used with another protocol layer, e.g. SCTP or TCP, used together with
together with DTLS. DTLS.
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.
Endpoints MUST support SHA-256 for generating and verifying the Endpoints MUST support the algorithms defined in **** Endpoints MUST
fingerprint value associated with the DTLS association. The use of support SHA-256 for generating and verifying the fingerprint value
SHA-256 is preferred. associated with the DTLS association. The use of 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 the The certificate received during the DTLS handshake MUST match the
fingerprint received in the SDP "fingerprint" attribute. If the fingerprint received in the SDP "fingerprint" attribute. If the
fingerprint does not match the hashed certificate, then the endpoint fingerprint does not match the hashed certificate, then the endpoint
MUST tear down the media session immediately. Note that it is MUST tear down the media session immediately. Note that it is
permissible to wait until the other side's fingerprint has been permissible to wait until the other side's fingerprint has been
received before establishing the connection; however, this may have received before establishing the connection; however, this may have
undesirable latency effects. undesirable latency effects.
6.2. 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-connection'
attribute with a 'new' value in the offer. In addition, the offerer attribute with a 'new' value in the offer. In addition, the offerer
MUST insert an SDP 'setup' attribute according to the procedures in MUST insert an SDP 'setup' attribute according to the procedures in
[RFC4145], and an SDP 'fingerprint' attribute according to the [RFC4145], and an SDP 'fingerprint' attribute according to the
procedures in [RFC4572], in the offer. 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.
6.3. 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 connection' attribute with a 'new' value, or if the answerer receives
and offer that contains an 'dtls-connection' attribute with an and offer that contains an 'dtls-connection' attribute with an
'existing' value and the answerer determines (based on the criteria 'existing' value and the answerer determines (based on the criteria
for establishing a new DTLS association) that a new DTLS association for establishing a new DTLS association) that a new DTLS association
is to be established, the answerer MUST insert a 'new' value in the is to be established, the answerer MUST insert a 'new' value in the
associated answer. In addition, the answerer MUST insert an SDP associated answer. In addition, the answerer MUST insert an SDP
'setup' attribute according to the procedures in [RFC4145], and an 'setup' attribute according to the procedures in [RFC4145], and an
SDP 'fingerprint' attribute according to the procedures in [RFC4572], SDP 'fingerprint' attribute according to the procedures in [RFC4572],
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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- connection' attribute, the answerer MUST NOT insert a 'dtls-
connection' attribute in the answer. connection' 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 the offerer. ClientHello message towards the the offerer.
6.4. 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 connection' attribute with a 'new' value, and if the offerer becomes
DTLS client, the offerer MUST establish a DTLS association. If the DTLS client (based on the value of the SDP 'setup' attribute value
[RFC4145]), the offerer MUST establish a DTLS association. If the
offerer becomes DTLS server, it MUST wait for the answerer to 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-connection' attribute with an
'existing' value, the offerer will continue using the previously 'existing' value, the offerer will continue using the previously
established DTLS association. It is considered an error case if the established DTLS association. It is considered an error case if the
answer contains a 'dtls-connection' attribute with an 'existing' answer contains a 'dtls-connection' attribute with an 'existing'
value, and a DTLS association does not exist. value, and a DTLS association does not exist.
6.5. 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-connection' 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 an SDP 'fingerprint' attribute to the procedures in [RFC4145], and an SDP 'fingerprint' attribute
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
skipping to change at page 8, line 20 skipping to change at page 8, line 21
'dtls-connection' attribute with an 'existing' value in the offer. 'dtls-connection' attribute with an 'existing' value in the offer.
In addition, the offerer MUST insert an SDP 'setup' attribute with a In addition, the offerer MUST insert an SDP 'setup' attribute with a
value that does not change the previously negotiated DTLS roles, and value that does not change the previously negotiated DTLS roles, and
an SDP 'fingerprint' attribute with a value that does not change the an SDP 'fingerprint' attribute with a value that does not change the
previously sent fingerprint, in the offer. previously sent fingerprint, 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.
7. 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 An ICE restart [RFC5245] does not by default require a new DTLS
association to be established. association to be established.
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.
8. Transport Protocol Considerations 7. Transport Protocol Considerations
8.1. Transport Re-Usage 7.1. Transport Re-Usage
If DTLS is transported on top of a connection-oriented transport If DTLS is transported on top of a connection-oriented transport
protocol (e.g. TCP or SCTP), where all IP packets are acknowledged, protocol (e.g. TCP or SCTP), where all IP packets are acknowledged,
all DTLS packets associated with a previous DTLS association MUST be all DTLS packets associated with a previous DTLS association MUST be
acknowledged (or timed out) before a new DTLS association can be acknowledged (or timed out) before a new DTLS association can be
established on the same transport. established on the same transport.
9. SIP Considerations 8. SIP Considerations
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 'offerless 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, it MUST assign an SDP
connection attribute, with a 'new' value, to each 'm-' line that connection attribute, with a 'new' value, to each 'm-' line that
describes DTLS protected media. If ICE is used, the endpoint MUST describes DTLS protected media. If ICE is used, the endpoint MUST
allocate a new set of ICE candidates, in order to ensure that two allocate a new set of ICE candidates, in order to ensure that two
DTLS association would not be running over the same transport. DTLS association would not be running over the same transport.
10. RFC Updates 9. RFC Updates
10.1. 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.
10.2. Update to RFC 5763 9.2. Update to RFC 5763
Update to section 5: Update to section 5:
-------------------- --------------------
OLD TEXT: OLD TEXT:
5. Establishing a Secure Channel 5. Establishing a Secure Channel
The two endpoints in the exchange present their identities as part of The two endpoints in the exchange present their identities as part of
the DTLS handshake procedure using certificates. This document uses the DTLS handshake procedure using certificates. This document uses
skipping to change at page 14, line 29 skipping to change at page 14, line 29
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].
Note that Simple Traversal of the UDP Protocol through NAT (STUN) Note that Simple Traversal of the UDP Protocol through NAT (STUN)
packets are sent directly over UDP, not over DTLS. [RFC5764] packets are sent directly over UDP, not over DTLS. [RFC5764]
describes how to demultiplex STUN packets from DTLS packets and SRTP describes how to demultiplex STUN packets from DTLS packets and SRTP
packets. packets.
10.3. Update to RFC 7345 9.3. Update to RFC 7345
Update to section 4: Update to section 4:
-------------------- --------------------
OLD TEXT: OLD TEXT:
4. SDP Offerer/Answerer Procedures 4. SDP Offerer/Answerer Procedures
4.1. General 4.1. General
skipping to change at page 17, line 35 skipping to change at page 17, line 35
deleted. deleted.
NEW TEXT: NEW TEXT:
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].
11. 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-connection' 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.
12. IANA Considerations 11. IANA Considerations
12.1. Registration of New SDP Attribute
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 attributes in Section 12.1 to the table for SDP media it adds the SDP dtls-connection attribute to the table for SDP media
level attributes. level attributes.
Attribute name: dtls-connection Attribute name: dtls-connection
Type of attribute: media-level Type of attribute: media-level
Subject to charset: no Subject to charset: no
Purpose: TBD Purpose: TBD
Appropriate Values: see Section X Appropriate Values: see Section X
Contact name: Christer Holmberg Contact name: Christer Holmberg
13. Acknowledgements 12. Acknowledgements
Thanks to Justin Uberti, Martin Thomson, Paul Kyzivat and Jens Thanks to Justin Uberti, Martin Thomson, Paul Kyzivat and Jens
Guballa for providing comments and suggestions on the draft. Guballa for providing comments and suggestions on the draft.
14. 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-03
o Changes based on comments from Paul Kyzivat:
o - Modification of dtls-connection attribute section.
o - Removal of IANA considerations subsection.
o - Making note into normative text in o/a section.
o Changes based on comments from Martin Thompson:
o - Abbreviations section removed.
o - Clarify that a new DTLS association requires a new o/a
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-connection-id' attribute removed.
o - Additional SDP offer/answer procedures, related to certificates, o - Additional SDP offer/answer procedures, related to certificates,
added. added.
skipping to change at page 19, line 16 skipping to change at page 19, line 32
unchanged in associated answer. unchanged in associated answer.
o - SIP Considerations section added. o - SIP Considerations section added.
o - Section about multiple SDP fingerprint attributes added. o - Section about multiple SDP fingerprint attributes added.
Changes from draft-holmberg-mmusic-sdp-dtls-00 Changes from draft-holmberg-mmusic-sdp-dtls-00
o - Editorial changes and clarifications. o - Editorial changes and clarifications.
15. Normative References 14. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[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,
DOI 10.17487/RFC3261, June 2002, DOI 10.17487/RFC3261, June 2002,
 End of changes. 42 change blocks. 
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