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Versions: 00 01 02 03 04 05 06 07 draft-martinsen-mmusic-ice-dualstack-fairness

MMUSIC                                                          T. Reddy
Internet-Draft                                                  P. Patil
Intended status: Standards Track                                 D. Wing
Expires: April 7, 2013                                             Cisco
                                                         October 4, 2012


                    Happy Eyeballs Extension for ICE
                draft-reddy-mmusic-ice-happy-eyeballs-00

Abstract

   This document specifies requirements for algorithms that make ICE
   connectivity checks more aggressive to reduce delays in dual stack
   host 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-noticable delays wheen the IPv6 path is broken or
   excessively slow.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 7, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must



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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Notational Conventions  . . . . . . . . . . . . . . . . . . . . 3
   3.  Candidates Priority . . . . . . . . . . . . . . . . . . . . . . 3
   4.  Algorithm overview  . . . . . . . . . . . . . . . . . . . . . . 4
     4.1.  Processing the Results  . . . . . . . . . . . . . . . . . . 5
   5.  Relayed Candidates  . . . . . . . . . . . . . . . . . . . . . . 7
   6.  Setting Te, Tr and MAX_PAIRS_HAPPYEYE_STAGE . . . . . . . . . . 8
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
   8.  Security Considerations . . . . . . . . . . . . . . . . . . . . 8
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     9.1.  Normative References  . . . . . . . . . . . . . . . . . . . 8
     9.2.  Informative References  . . . . . . . . . . . . . . . . . . 9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 9































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1.  Introduction

   In situations where there are many IPv6 addresses, ICE [RFC5245] will
   prefer IPv6 [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 performing
   connectivity checks with both IPv6 and IPv4 candidates in parallel if
   IPv6 connectivity checks have not yet succeeded.  This document
   specifies requirements for any such algorithm, with the goals that
   the ICE agent need not be inordinately harmed with a simple
   parallelisation of IPv6 and IPv4 connectivity checks and ensuring
   that the priority of precedence defined in [RFC6724] be honored.

   For either of the address families, there is also a very realistic
   chance that connectivity checks for relayed candidates will always
   work.  There are scenarios where firewalls block connectivity checks
   for Host/Server Reflexive candidates or for IPv4 or for IPv6.  This
   document also proposes an optimization where connectivity checks with
   relayed checks are performed earlier than usual if connectivity
   checks using other candidates do not succeed.


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
   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.




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   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 in Section 4 IPv6 candidate pairs will be
   tested first as usual, but if connectivity checks are not successful
   after a certain period of time, the algorithm will become more
   aggressive and connectivity checks using IPv6/IPv4 host/
   server-reflexive candidates will be performed simultaneously.  If
   connectivity checks with IPv6 candidate pairs do not yield any
   successful result then ICE endpoints can immediately start sending
   media using IPv4 host/server-reflexive candidates.

   Note: [RFC6724] permits administrator to change the policy table to
   prefer IPv4 addresses over IPv6 addresses in which case the algorithm
   described in the next section is reversed.


4.  Algorithm overview

   The Happy Eyeballs Extension for ICE is governed by a timer (Te) that
   is started just before carrying out the ICE connectivity checks for
   each check list under the following conditions:

   1.  when the candidates pairs include IPv6 and IPv4 addresses

   2.  list of IPv6 candidate pairs is higher than a configured
       threshold (MAX_PAIRS_HAPPYEYE_STAGE_I).  [RFC5245] recommends a
       limit of 100 for the candidate pairs.

   When the timer (Te) fires, if the connectivity check using IPv6
   candidate pairs are not yet successful and if the number of IPv6
   candidate pairs with remote candidates of type host in the check list
   that are in Waiting and Frozen state are non-zero, the ICE agent
   performs the following Happy Eyeball steps in parallel with the
   regular ICE Ordinary checks:




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   o  Find the highest priority pair in the checklist that is in the
      Waiting state with candidate address family being IPv4 and remote
      candidate of type host.  If there are no remote IPv6 candidates of
      type server-reflexive then IPv4 remote candidates of type server-
      reflexive will be added to the search.

      1.  If there is such a pair then perform ICE connectivity check on
          this pair and set the state of the candidate pair to In-
          Progress.

      2.  If there is no such pair find the highest priority pair in the
          checklist that is in the Frozen state with candidate address
          family being IPv4 and remote candidate of type host candidate.
          If there are no remote IPv6 candidates of type server-
          reflexive then IPv4 remote candidates of type server-reflexive
          will be added to the search.  If there is such pair in Frozen
          state then unfreeze the pair, perform connectivity check on
          this pair and set the state of the candidate pair to In-
          Progress.

   o  The above mentioned steps will be followed every Ta milliseconds
      and stopped when any of the below conditions are met:

      1.  All IPv6 candidate pairs with remote candidates of type host
          in the check list are in any of the following states
          Succeeded, In-Progress or Failed states.  The parallel
          activity is not required beyond this point because the regular
          ICE algorithm will itself pick up IPv4 candidate pairs not yet
          tested.

      2.  All IPv4 candidate pairs with remote candidates of type host/
          server reflexive are in any of the following states Succeeded,
          In-Progress or Failed states.

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



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   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
     |                                                             |
     |  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<-----------------------|
     |  Bind Req USE-CAND                                          |
     |  using IPv6 after Ta                 Bind Req               |
     |------------------>X                 using IPv6              |
     |                                    X<-----------------------|
     |                                                             |
   [Timer Te fires, try IPv4 in parallel]                          |
     |                                                             |
     |  Bind Req USE-CAND                                          |
     |  using IPv4                                                 |
     |------------------------------------------------------------>|
     |  Bind Req USE-CAND                                          |
     |  using IPv6 after Ta                                        |
     |------------------> X                                        |
     |                                        Bind Resp            |
     |                                        using IPv4           |
     |<----------------------------------------------------------- |
     |          RTP                                                |
     |============================================================>|
     |                                       Bind Req              |
     |                                       using IPv4            |
     |<------------------------------------------------------------|
     |  Bind Response                                              |
     |  using IPv4                                                 |
     |------------------------------------------------------------>|
     |          RTP                                                |
     |<===========================================================>|

                Figure 2: Happy Eyeballs Extension for ICE




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5.  Relayed Candidates

   The optimization proposes doing connectivity checks with relayed
   candidates in parallel with other candidates.  The algorithm does not
   make a distinction between IPv6/IPv4 relayed candidates and will
   choose the existing order among relayed candidate pair defined by
   ICE.  If ICE connectivity check is successful using a relayed
   candidate from either of the IP address families, the ICE agent can
   stop connectivity checks for other relayed candidates.

   This part of the Happy Eyeballs Extension for ICE is governed by a
   timer (Tr) that is started just before carrying out the ICE
   connectivity checks for each check list under the following
   conditions:

   1.  when the candidates pairs include IPv6 and IPv4 relayed addresses

   2.  list of candidate pairs is higher than a configured threshold
       (MAX_PAIRS_HAPPYEYE_STAGE_I).

   When the timer (Tr) fires, If no ICE connectivity checks are
   successful as yet and if ICE Connectivity checks using IPv6 and IPv4
   local relayed candidates have not yet been attempted then the
   following steps will be started by the ICE agent in parallel with
   other connectivity checks:

   o Find the highest priority pair in the checklist that is in the
   Waiting state with local candidate of type relayed.

   1.  If there is such a pair then perform ICE connectivity check on
       this pair and set the state of the candidate pair to In-Progress.

   2.  If there is no such pair find the highest priority pair in the
       checklist that is in the Frozen state with local candidate of
       type relayed.  If there is such pair in Frozen state then
       unfreeze the pair, perform connectivity check on this pair and
       set the state of the candidate pair to In-Progress.

   If ICE connectivity checks using relayed candidate is successful then
   ICE Agent will performs as usual "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 local relayed
   candidates is successful for each component of the media stream and
   connectivity checks using higher priority candidate pairs has not yet
   succeeded then conclude ICE for the media stream and proceed to send
   media using local relayed candidate.




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   However ICE connectivity checks MUST be continued and if the check
   succeeds for a pair whose priority is higher than the previously
   selected candidate pair then media session will be moved to this
   pair.  Hence media will only be sent briefly on TURN relays.
   Additional TURN server load is created due to this recommendations,
   especially when connectivity check using IPv6/IPv4 host/
   server-reflexive candidates are not completing quickly and the side
   affect could be that RTP receivers will receive packets out of order
   during switchover.


6.  Setting Te, Tr and MAX_PAIRS_HAPPYEYE_STAGE

   The value of Ta, Tr, MAX_PAIRS_HAPPYEYE_STAGE_I,
   MAX_PAIRS_HAPPYEYE_STAGE_II and SHOULD be configurable, and SHOULD
   have a default of:

                      Te : 150ms
                      Tr : 500ms
                      MAX_PAIRS_HAPPYEYE_STAGE_I  : 12
                      MAX_PAIRS_HAPPYEYE_STAGE_II :  6

                         Figure 3: Default Values


7.  IANA Considerations

   None.


8.  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.


9.  References

9.1.  Normative References

   [I-D.keranen-mmusic-ice-address-selection]
              Keranen, 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.




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   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [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.

   [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









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   Dan Wing
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, California  95134
   USA

   Email: dwing@cisco.com












































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