One document matched: draft-reddy-mmusic-ice-happy-eyeballs-01.xml
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<rfc category="std" docName="draft-reddy-mmusic-ice-happy-eyeballs-01"
ipr="trust200902">
<front>
<title abbrev="Happy Eyeballs for ICE ">Happy Eyeballs Extension for
ICE</title>
<author fullname="Tirumaleswar Reddy" initials="T." surname="Reddy">
<organization abbrev="Cisco">Cisco Systems, Inc.</organization>
<address>
<postal>
<street>Cessna Business Park, Varthur Hobli</street>
<street>Sarjapur Marathalli Outer Ring Road</street>
<city>Bangalore</city>
<region>Karnataka</region>
<code>560103</code>
<country>India</country>
</postal>
<email>tireddy@cisco.com</email>
</address>
</author>
<author fullname="Prashanth Patil" initials="P." surname="Patil">
<organization abbrev="Cisco">Cisco Systems, Inc.</organization>
<address>
<postal>
<street>Cessna Business Park, Varthur Hobli</street>
<street>Sarjapur Marthalli Outer Ring Road</street>
<city>Bangalore</city>
<region>Karnataka</region>
<code>560103</code>
<country>India</country>
</postal>
<email>praspati@cisco.com</email>
</address>
</author>
<author fullname="Dan Wing" initials="D." surname="Wing">
<organization abbrev="Cisco">Cisco Systems, Inc.</organization>
<address>
<postal>
<street>170 West Tasman Drive</street>
<city>San Jose</city>
<region>California</region>
<code>95134</code>
<country>USA</country>
</postal>
<email>dwing@cisco.com</email>
</address>
</author>
<date />
<workgroup>MMUSIC</workgroup>
<abstract>
<t>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.</t>
</abstract>
</front>
<middle>
<section anchor="introduction" title="Introduction">
<t>In situations where there are many IPv6 addresses, <xref
target="RFC5245">ICE</xref> will prefer IPv6 candidates <xref
target="RFC6724"></xref> 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.</t>
<t>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.</t>
</section>
<section anchor="notation" title="Notational Conventions">
<t>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 <xref
target="RFC2119"></xref>.</t>
<t>This note uses terminology defined in <xref
target="RFC5245"></xref>.</t>
</section>
<section anchor="problem_stmt" title="Candidates Priority">
<t>A prioritization formula is used by ICE <xref
target="RFC5245"></xref> 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 <xref target="RFC6724"> </xref> as part of the prioritization
formula for IPv6 host candidates and <xref
target="I-D.keranen-mmusic-ice-address-selection"></xref> updates the
ICE rules on how IPv6 host candidates are selected.</t>
<t>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 <xref target="RFC6724"></xref>. IPv6 server
reflexive candidates have higher precedence than IPv4 server reflexive
candidate since NPTv6 is stateless and transport-agnostic.</t>
<t><figure anchor="Figure1"
title="Candidate Preferences in decreasing order">
<artwork align="center"><![CDATA[ (highest) IPv6 Host Candidate
IPv4 Host Candidate
IPv6 Server Reflexive Candidate
IPv4 Server Reflexive Candidate
IPv6 Relayed Transport Candidate
(lowest) IPv4 Relayed Transport Candidate ]]></artwork>
</figure></t>
<t>By using the technique described in <xref
target="alg_overview"></xref>, 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.</t>
<t>Note: The algorithm works even if the administrator changes the
policy table to prefer IPv4 addresses over IPv6 addresses as defined in
<xref target="RFC6724"></xref></t>
</section>
<section anchor="alg_overview" title="Algorithm overview">
<t>The Happy Eyeballs Extension for ICE algorithm proposes the
following:</t>
<t><list style="numbers">
<t>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.</t>
<t>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 <xref
target="RFC5245"></xref>)<list style="letters">
<t>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.</t>
<t>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.</t>
</list></t>
</list></t>
<t>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.</t>
<t>The following figure illustrates the result of the algorithm on
candidate pairs:</t>
<t><figure>
<artwork><![CDATA[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
IPv6 Host Candidate-7 pair
IPv6 Server Reflexive Candidate pair
IPv6 Relayed Transport Candidate pair
(lowest) IPv4 Relayed Transport Candidate pair]]></artwork>
</figure></t>
<section anchor="result" title="Processing the Results">
<t>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 <xref target="RFC5245"></xref>),
"Constructing a Valid Pair" (Section 7.1.3.2.2 of <xref
target="RFC5245"></xref>), "Updating Pair States" (Section 7.1.3.2.3
of <xref target="RFC5245"></xref>), "Updating the Nominated Flag"
(Section 7.1.3.2.4 of <xref target="RFC5245"></xref>).</t>
<t>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.</t>
<t>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.</t>
<figure anchor="Figure2" title="Happy Eyeballs Extension for ICE">
<artwork align="left"><![CDATA[ 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 |
|------------------------------------------------------------>|
| Bind Resp |
| using IPv4 |
|<----------------------------------------------------------- |
| RTP |
|============================================================>|
| Bind Req |
| using IPv4 |
|<------------------------------------------------------------|
| Bind Response |
| using IPv4 |
|------------------------------------------------------------>|
| RTP |
|<===========================================================>|
]]></artwork>
</figure>
</section>
</section>
<section title="Indicating Happy-Eyeballs">
<t>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) <xref target="RFC4566"></xref> 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.</t>
</section>
<section title="IANA Considerations">
<t>IANA is requested to register "happy-eyeballs" option identifier
under the "ICE Options" <xref target="RFC6336"></xref> registry.</t>
<t>The required registration information is as follows:</t>
<t>Option identifier: happy-eyeballs</t>
<t>Contact: Tirumaleswar Reddy, tireddy@cisco.com</t>
<t>Change control: IETF</t>
<t>Description: Existence of this option identifier indicates that Happy
Eyeballs Extension for ICE algorithm is used.</t>
<t>Reference: RFCXXXX</t>
<t>[RFC editor: replace XXXX with the RFC number of this document]</t>
</section>
<section anchor="security" title="Security Considerations">
<t>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 <xref
target="RFC5245"></xref> apply to this use.</t>
</section>
<section anchor="ack" title="Acknowledgements">
<t>The authors would like to thank Bernard Aboba for his inputs.</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include="reference.RFC.2119"?>
<?rfc include="reference.RFC.3484"?>
<?rfc include="reference.RFC.5766"?>
<?rfc include="reference.RFC.5245"?>
<?rfc include="reference.RFC.5389"?>
<?rfc include="reference.RFC.4566"?>
<?rfc include='reference.I-D.keranen-mmusic-ice-address-selection'?>
<?rfc include="reference.RFC.6724"?>
<?rfc include="reference.RFC.4566"
?>
<?rfc include="reference.RFC.6336"?>
</references>
<references title="Informative References">
<?rfc include='reference.RFC.2663'?>
<!---->
</references>
</back>
</rfc>
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