MMUSIC T. Reddy
Internet-Draft P. Patil
Intended status: Standards Track D. Wing
Expires: January 12, 2014 Cisco
July 11, 2013
Happy Eyeballs Extension for ICE
draft-reddy-mmusic-ice-happy-eyeballs-01
Abstract
This document specifies requirements for algorithms that make ICE
connectivity checks more responsive by reducing delays in dual-stack
host ICE connectivity checks when there is a path failure for the
address family preferred by the application or by the operating
system. As IPv6 is usually preferred, the procedures in this
document helps avoid user-noticeable delays when the IPv6 path is
broken or excessively slow.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on January 12, 2014.
Copyright Notice
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Notational Conventions . . . . . . . . . . . . . . . . . . . 2
3. Candidates Priority . . . . . . . . . . . . . . . . . . . . . 2
4. Algorithm overview . . . . . . . . . . . . . . . . . . . . . 3
4.1. Processing the Results . . . . . . . . . . . . . . . . . 5
5. Indicating Happy-Eyeballs . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.1. Normative References . . . . . . . . . . . . . . . . . . 7
9.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
In situations where there are many IPv6 addresses, ICE [RFC5245] will
prefer IPv6 candidates [RFC6724] and will attempt connectivity checks
on all the IPv6 candidates before trying an IPv4 candidate. If the
IPv6 path is broken, this fallback to IPv4 can consume a lot of time,
harming user satisfaction of dual-stack devices.
This document describes an algorithm that makes ICE connectivity
checks more responsive to failures of an address family by reordering
the candidate pairs such that IPv6 and IPv4 candidates get a fair
chance during connectivity checks. This document specifies
requirements for any such algorithm, with the goals that the ICE
agent need not be inordinately harmed with a simple reordering of the
candidate pairs.
2. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
This note uses terminology defined in [RFC5245].
3. Candidates Priority
A prioritization formula is used by ICE [RFC5245] so that most
preferred address pairs are tested first, and if a sufficiently good
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pair is discovered, the tests can be stopped. With IPv6, addresses
obtained from local network interfaces, called host candidates, are
recommended as high-priority ones to be tested first since if they
work, they provide usually the best path between the two hosts. The
ICE specification recommends to use the rules defined in [RFC6724] as
part of the prioritization formula for IPv6 host candidates and
[I-D.keranen-mmusic-ice-address-selection] updates the ICE rules on
how IPv6 host candidates are selected.
For dual-stack hosts the preference for IPv6 host candidates is
higher than IPv4 host candidates based on precedence value of IP
addresses described in [RFC6724]. IPv6 server reflexive candidates
have higher precedence than IPv4 server reflexive candidate since
NPTv6 is stateless and transport-agnostic.
(highest) IPv6 Host Candidate
IPv4 Host Candidate
IPv6 Server Reflexive Candidate
IPv4 Server Reflexive Candidate
IPv6 Relayed Transport Candidate
(lowest) IPv4 Relayed Transport Candidate
Figure 1: Candidate Preferences in decreasing order
By using the technique described in Section 4, if there are both IPv6
and IPv4 addresses in the check list, and the first 'N' candidates
are of the same IP address family, then the highest-priority
candidate pair of the other address family is promoted to position N
in the check list thus making ICE connectivity checks more responsive
to failures of an address family.
Note: The algorithm works even if the administrator changes the
policy table to prefer IPv4 addresses over IPv6 addresses as defined
in [RFC6724]
4. Algorithm overview
The Happy Eyeballs Extension for ICE algorithm proposes the
following:
1. Indicate support for ICE Happy Eyeballs in the SDP offer if the
end-point is dual-stack. The end-point will also include the
position 'N' at which promotion is to occur.
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2. After SDP offer/answer exchange if both end points support ICE
Happy Extension for ICE algorithm the following steps are
performed by the ICE agents after computing the candidate pair
priority, ordering and pruning the pairs (section 5.7.2, 5.7.3 of
[RFC5245])
a. If the first 'N' candidate pairs in the check list are of the
same IP address family, then the highest-priority candidate
pair of the other address family is promoted to position 'N'
in the list.
b. Step b is repeated for candidate pairs that are next in the
check list. This is continued until all candidate pairs of
the preferred address family are exhausted.
The result of these steps is that after every consecutive 'N'
candidate pairs of the preferred family, a candidate pair of the
other family is inserted.
The following figure illustrates the result of the algorithm on
candidate pairs:
Before Happy Eyeballs Extension for ICE algorithm :
----------------------------------------------------
(highest) IPv6 Host Candidate-1 pair
IPv6 Host Candidate-2 pair
IPv6 Host Candidate-3 pair
IPv6 Host Candidate-4 pair
IPv6 Host Candidate-5 pair
IPv6 Host Candidate-6 pair
IPv6 Host Candidate-7 pair
IPv4 Host Candidate pair
IPv6 Server Reflexive Candidate pair
IPv4 Server Reflexive Candidate pair
IPv6 Relayed Transport Candidate pair
(lowest) IPv4 Relayed Transport Candidate pair
After Happy Eyeballs Extension for ICE algorithm :
--------------------------------------------------
(highest) IPv6 Host Candidate-1 pair
IPv6 Host Candidate-2 pair
IPv6 Host Candidate-3 pair
IPv4 Host Candidate pair ---> Promoted pair
IPv6 Host Candidate-4 pair
IPv6 Host Candidate-5 pair
IPv6 Host Candidate-6 pair
IPv4 Server Reflexive Candidate pair ---> Promoted pair
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IPv6 Host Candidate-7 pair
IPv6 Server Reflexive Candidate pair
IPv6 Relayed Transport Candidate pair
(lowest) IPv4 Relayed Transport Candidate pair
4.1. Processing the Results
If ICE connectivity checks using an IPv4 candidate is successful then
ICE Agent will performs as usual "Discovering Peer Reflexive
Candidates" (Section 7.1.3.2.1 of [RFC5245]), "Constructing a Valid
Pair" (Section 7.1.3.2.2 of [RFC5245]), "Updating Pair States"
(Section 7.1.3.2.3 of [RFC5245]), "Updating the Nominated Flag"
(Section 7.1.3.2.4 of [RFC5245]).
If ICE connectivity checks using an IPv4 candidate is successful for
each component of the media stream and connectivity checks using IPv6
candidates is not yet successful, the ICE endpoint will declare
victory, conclude ICE for the media stream and start sending media
using IPv4. However, it is also possible that ICE endpoint continues
to perform ICE connectivity checks with IPv6 candidate pairs and if
checks using higher-priority IPv6 candidate pair is successful then
media stream can be moved to the IPv6 candidate pair. Continuing to
perform connectivity checks can be useful for subsequent connections,
to optimize which connectivity checks are tried first. Such
optimization is out of scope of this document.
The following diagram shows the behaviour during the connectivity
check when Alice calls Bob and Agent Alice is the controlling agent
and uses the aggressive nomination algorithm. "USE-CAND" implies the
presence of the USE-CANDIDATE attribute.
Alice Bob
| |
| SDP Offer; a=happy-eyeballs:2 |
| SDP Answer; a=happy-eyeballs:2 |
| |
| Bind Req USE-CAND Bind Req |
| using IPv6 using IPv6 |
|------------------>X X<-----------------------|
| Bind Req USE-CAND Bind Req |
| using IPv6 after Ta using IPv6 |
|------------------>X X<-----------------------|
| |
[after connectivity checks for 2 IPv6 addresses, try IPv4] |
| |
| Bind Req USE-CAND |
| using IPv4 |
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|------------------------------------------------------------>|
| Bind Resp |
| using IPv4 |
|<----------------------------------------------------------- |
| RTP |
|============================================================>|
| Bind Req |
| using IPv4 |
|<------------------------------------------------------------|
| Bind Response |
| using IPv4 |
|------------------------------------------------------------>|
| RTP |
|<===========================================================>|
Figure 2: Happy Eyeballs Extension for ICE
5. Indicating Happy-Eyeballs
To indicate that Happy Eyeballs Extension for ICE algorithm defined
in this document is used, the ICE offerer MUST include ice-options
attribute with "happy-eyeballs:N" option identifier in the Session
Description Protocol (SDP) [RFC4566] ICE offer, where N indicates the
position at which promotion is to occur. If the ICE offer does not
include this option tag, the answerer SHOULD NOT utilize the updated
ICE algorithm defined in this document. If the offer included the
option tag and the answerer supports this specification, the answerer
SHOULD add the same option tag to the response and use the Happy
Eyeballs Extension for ICE algorithm. If the ICE answer does not
contain the option tag, the offerer SHOULD NOT use the updated ICE
algorithm. Recommended value for 'N' is 3. As IPv6 becomes more
prevalent, the value of 'N' can be increased as desired.
6. IANA Considerations
IANA is requested to register "happy-eyeballs" option identifier
under the "ICE Options" [RFC6336] registry.
The required registration information is as follows:
Option identifier: happy-eyeballs
Contact: Tirumaleswar Reddy, tireddy@cisco.com
Change control: IETF
Description: Existence of this option identifier indicates that Happy
Eyeballs Extension for ICE algorithm is used.
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Reference: RFCXXXX
[RFC editor: replace XXXX with the RFC number of this document]
7. Security Considerations
STUN connectivity check using MAC computed during key exchanged in
the signaling channel provides message integrity and data origin
authentication as described in section 2.5 of [RFC5245] apply to this
use.
8. Acknowledgements
The authors would like to thank Bernard Aboba for his inputs.
9. References
9.1. Normative References
[I-D.keranen-mmusic-ice-address-selection]
Keraenen, A. and J. Arkko, "Update on Candidate Address
Selection for Interactive Connectivity Establishment
(ICE)", draft-keranen-mmusic-ice-address-selection-01
(work in progress), July 2012.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3484] Draves, R., "Default Address Selection for Internet
Protocol version 6 (IPv6)", RFC 3484, February 2003.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006.
[RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
(ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols", RFC 5245, April
2010.
[RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
"Session Traversal Utilities for NAT (STUN)", RFC 5389,
October 2008.
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[RFC5766] Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using
Relays around NAT (TURN): Relay Extensions to Session
Traversal Utilities for NAT (STUN)", RFC 5766, April 2010.
[RFC6336] Westerlund, M. and C. Perkins, "IANA Registry for
Interactive Connectivity Establishment (ICE) Options", RFC
6336, July 2011.
[RFC6724] Thaler, D., Draves, R., Matsumoto, A., and T. Chown,
"Default Address Selection for Internet Protocol Version 6
(IPv6)", RFC 6724, September 2012.
9.2. Informative References
[RFC2663] Srisuresh, P. and M. Holdrege, "IP Network Address
Translator (NAT) Terminology and Considerations", RFC
2663, August 1999.
Authors' Addresses
Tirumaleswar Reddy
Cisco Systems, Inc.
Cessna Business Park, Varthur Hobli
Sarjapur Marathalli Outer Ring Road
Bangalore, Karnataka 560103
India
Email: tireddy@cisco.com
Prashanth Patil
Cisco Systems, Inc.
Cessna Business Park, Varthur Hobli
Sarjapur Marthalli Outer Ring Road
Bangalore, Karnataka 560103
India
Email: praspati@cisco.com
Dan Wing
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, California 95134
USA
Email: dwing@cisco.com
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