MMUSIC T. Reddy
Internet-Draft P. Patil
Intended status: Standards Track P. Martinsen
Expires: August 1, 2014 Cisco
January 28, 2014
Happy Eyeballs Extension for ICE
draft-reddy-mmusic-ice-happy-eyeballs-05
Abstract
This document provides guidelines on how to make ICE [RFC5245]
conclude faster in IPv4/IPv6 dual-stack scenarios where broken paths
exist. This will lead to more sustained IPv6 deployment as users
will no longer have an incentive to disable IPv6.
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 August 1, 2014.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Notational Conventions . . . . . . . . . . . . . . . . . . . 2
3. Improving ICE Dual-stack Fairness . . . . . . . . . . . . . . 2
4. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 3
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
8. Normative References . . . . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
There is a need to introduce more fairness in the handling of
connectivity checks for different IP address families in dual-stack
IPv4/IPv6 ICE scenarios. Section 4.1.2.1 of ICE [RFC5245] points to
[RFC3484] for prioritizing among the different IP families.
[RFC3484] is obsoleted by [RFC6724] but following the recommendations
from the updated RFC will lead to prioritization of IPv6 over IPv4
for the same candidate type. Due to this, connectivity checks for
candidates of the same type (HOST, RFLX, RELAY) are sent such that an
IP address family is completely depleted before checks on the other
address family are started. This results in user noticeable setup
delays if the path for the prioritized address family is broken.
To avoid such user noticeable delays when either IPv6 or IPv4 path is
broken, this specification encourages intermingling the different
address families when connectivity checks are conducted. Introducing
IP address family fairness into ICE connectivity checks will lead to
more sustained dual-stack IPv4/IPv6 deployment as users will no
longer have an incentive to disable IPv6. The cost is a small
penalty to the address type that otherwise would have been
prioritized.
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 document uses terminology defined in [RFC5245].
3. Improving ICE Dual-stack Fairness
Candidates SHOULD be prioritized such that a long sequence of
candidates belonging to the same address family will be intermingled
with candidates from an alternate IP family. For example, promoting
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IPv4 candidates in the presence of many IPv6 candidates such that an
IPv4 address candidate is always present after a small sequence of
IPv6 candidates, i.e., reordering candidates such that both IPv6 and
IPv4 candidates get a fair chance during the connectivity check
phase. This makes ICE connectivity checks more responsive to broken
path failures of an address family.
An ICE agent can choose an algorithm or a technique of its choice to
ensure that the resulting check lists have a fair intermingled mix of
IPv4 and IPv6 address families. Modifying the check list directly
can lead to uncoordinated local and remote check lists that result in
ICE taking longer to complete. The best approach is to modify the
formula for calculating the candidate priority value described in ICE
[RFC5245] section 4.1.2.1.
4. Compatibility
ICE [RFC5245] section 4.1.2 states that the formula in section
4.1.2.1 SHOULD be used to calculate the candidate priority. The
formula is as follows:
priority = (2^24)*(type preference) +
(2^8)*(local preference) +
(2^0)*(256 - component ID)
ICE [RFC5245] section 4.1.2.2 has guidelines for how the type
preference value should be chosen. Instead of having a static value
for IPv4 and a static value for IPv6 type of addresses, it is
possible to choose this value dynamically in such a way that IPv4 and
IPv6 address candidate priorities ends up intermingled.
The local and remote agent can have different algorithms for choosing
the type preference value without any impact on coordination between
the local and remote check list.
The check list is made up by candidate pairs. A candidate pair is
two candidates paired up and given a candidate pair priority as
described in [RFC5245] section 5.7.2. Using the pair priority
formula:
pair priority = 2^32*MIN(G,D) + 2*MAX(G,D) + (G>D?1:0)
Where G is the candidate provided by the controlling agent and D the
priority provided by the controlled agent. This ensures that the
local and remote check lists are coordinated.
Even if the two agents have different algorithms for choosing the
candidate priority value to get an intermingled set of IPv4 and IPv6
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candidates, the resulting checklist, that is a list sorted by the
pair priority value, will be identical on the two agents.
The agent that has promoted IPv4 cautiously i.e. lower IPv4 candidate
priority values compared to the other agent, will influence the check
list the most due to (2^32*MIN(G,D)) in the formula.
These recommendations are backward compatible with a standard ICE
implementation. If the other agent have IPv4 candidates with higher
priorities due to intermingling, the effect is canceled when the
checklist is formed and the pair priority formula is used to
calculate the pair priority.
5. IANA Considerations
None.
6. 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.
7. Acknowledgements
Authors would like to thank Dan Wing, Ari Keranen, Bernard Aboba,
Martin Thomson and Jonathan Lennox for their comments and review.
8. Normative References
[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.
[RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
(ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols", RFC 5245, April
2010.
[RFC6724] Thaler, D., Draves, R., Matsumoto, A., and T. Chown,
"Default Address Selection for Internet Protocol Version 6
(IPv6)", RFC 6724, September 2012.
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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.
Bangalore
India
Email: praspati@cisco.com
Paal-Erik Martinsen
Cisco Systems, Inc.
Philip Pedersens Vei 22
Lysaker, Akershus 1325
Norway
Email: palmarti@cisco.com
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