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


   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

   This Internet-Draft is submitted in full conformance with the
   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 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

2.  Notational Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   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.  Compatibility

   ICE [RFC5245] section 4.1.2 states that the formula in section 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 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

        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


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

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

   [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


   Prashanth Patil
   Cisco Systems, Inc.


   Paal-Erik Martinsen
   Cisco Systems, Inc.
   Philip Pedersens Vei 22
   Lysaker, Akershus  1325


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