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draft-reddy-mmusic-ice-happy-eyeballs-06.xml
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<?xml version="1.0" encoding="US-ASCII"?>
<!DOCTYPE rfc SYSTEM "rfc2629.dtd">
<?rfc toc="yes"?>
<?rfc tocompact="yes"?>
<?rfc tocdepth="3"?>
<?rfc tocindent="yes"?>
<?rfc symrefs="yes"?>
<?rfc sortrefs="yes"?>
<?rfc comments="yes"?>
<?rfc inline="yes"?>
<?rfc compact="yes"?>
<?rfc subcompact="no"?>
<rfc category="std" docName="draft-reddy-mmusic-ice-happy-eyeballs-06"
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>[email protected]</email>
</address>
</author>
<author fullname="Prashanth Patil" initials="P." surname="Patil">
<organization abbrev="Cisco">Cisco Systems, Inc.</organization>
<address>
<postal>
<street/>
<city>Bangalore</city>
<country>India</country>
</postal>
<email>[email protected]</email>
</address>
</author>
<author fullname="Paal-Erik Martinsen" initials="P.E" surname="Martinsen">
<organization abbrev="Cisco">Cisco Systems, Inc.</organization>
<address>
<postal>
<street>Philip Pedersens Vei 22</street>
<city>Lysaker</city>
<region>Akershus</region>
<code>1325</code>
<country>Norway</country>
</postal>
<email>[email protected]</email>
</address>
</author>
<date/>
<workgroup>MMUSIC</workgroup>
<abstract>
<t>This document provides guidelines on how to make Interactive
Connectivity Establishment (ICE) conclude faster in IPv4/IPv6
dual-stack scenarios where broken paths exist.</t>
</abstract>
</front>
<middle>
<section anchor="introduction" title="Introduction">
<t>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 <xref target="RFC5245"/>
points to <xref target="RFC3484"/> for prioritizing among the different
IP families. <xref target="RFC3484"/> is obsoleted by <xref
target="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.</t>
<t>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.</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"/>.</t>
<t>This document uses terminology defined in
<xref target="RFC5245"/>.</t>
</section>
<section title="Improving ICE Dual-stack Fairness">
<t>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 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.</t>
<t>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
or in the worst case scenario fail. The best approach is to
modify the formula for calculating the candidate priority value
described in ICE <xref target="RFC5245"/> section 4.1.2.1.</t>
</section>
<section anchor="compability" title="Compatibility">
<t>ICE <xref target="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:</t>
<t><figure>
<artwork align="left"><![CDATA[
priority = (2^24)*(type preference) +
(2^8)*(local preference) +
(2^0)*(256 - component ID)
]]></artwork>
</figure></t>
<t>ICE <xref target="RFC5245"/> section 4.1.2.2 has guidelines
for how the type preference and local preference value should be
chosen. Instead of having a static value for IPv4 and a static
value for IPv6 type of addresses for the local preference, it is
possible to choose this value dynamically in such a way that
IPv4 and IPv6 address candidate priorities ends up intermingled
within the same candidate type (HOST, RFLX, RELAY).</t>
<t>The local and remote agent can have different algorithms for choosing
the local preference value without impacting the synchronization between the
local and remote check list.</t>
<t>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
<xref target="RFC5245"/> section 5.7.2. Using the pair priority
formula:</t>
<t><figure>
<artwork align="left"><![CDATA[
pair priority = 2^32*MIN(G,D) + 2*MAX(G,D) + (G>D?1:0)
]]></artwork>
</figure></t>
<t>Where G is the candidate priority provided by the controlling agent and D the
candidate priority provided by the controlled agent. This ensures that the local
and remote check lists are coordinated.</t>
<t>Even if the two agents have different algorithms for choosing
the candidate priority value to get an intermingled set of IPv4
and IPv6 candidates, the resulting checklist, that is a list
sorted by the pair priority value, will be identical on the two
agents.</t>
<t>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.</t>
<t>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.</t>
</section>
<section title="Example Algorithm for Choosing the Local Preference">
<t>The value space for the local preference is from 0 to 65535
inclusive. This value space can be divided up in chunks for each
IP address family.
</t>
<t>
An IPv6 and IPv4 start priority must be given. In this example
IPv6 starts at 60000 and IPv4 at 59000. This leaves enough
address space to further play with the values if pr interface
priorities needs to be added. The highest value should be given
to the address family that should be prioritized.
</t>
<t>
<figure>
<artwork align="left"><![CDATA[
IPv6 IPv4
Start Start
65535 60k 59k 58k 57k 56k 55k 0
+--------+------+------+------+------+------+---------------------+
| | IPv6 | IPv4 | IPv6 | IPv4 | IPv6 | |
| | (1) | (1) | (2) | (2) | (3) | |
+--------+------+------+------+------+------+---------------------+
<- N->
]]></artwork>
</figure>
</t>
<t>
The local preference can be calculated by the given formula:
</t>
<t>
<figure>
<artwork align="left"><![CDATA[
local_preference = N*2*(Cn/Cmax)
]]></artwork>
</figure>
</t>
<t>
Where N is the absolute value of IPv6_start-IPv4_start. This
ensures a positive number even if IPv4 is the highest
priority. Cn is the number of current candidates of a specific
IP address type and candidate type (HOST, SRFLX, RELAY). Cmax is
the number of allowed consecutive candidates of the same IP address
type.
</t>
<t>
Using the values N=abs(60000-59000) and Cmax = 2 yields the
following sorted local candidate list:
<figure>
<artwork align="left"><![CDATA[
(1) HOST IPv6 (1) Priority: 2129289471
(2) HOST IPv6 (2) Priority: 2129289470
(3) HOST IPv4 (1) Priority: 2129033471
(4) HOST IPv4 (2) Priority: 2129033470
(5) HOST IPv6 (1) Priority: 2128777471
(6) HOST IPv6 (2) Priority: 2128777470
(7) HOST IPv4 (1) Priority: 2128521471
(8) HOST IPv4 (2) Priority: 2128521470
(9) HOST IPv6 (1) Priority: 2128265471
(10) HOST IPv6 (2) Priority: 2128265470
(11) SRFLX IPv6 (1) Priority: 1693081855
(12) SRFLX IPv6 (2) Priority: 1693081854
(13) SRFLX IPv4 (1) Priority: 1692825855
(14) SRFLX IPv4 (2) Priority: 1692825854
(15) RELAY IPv6 (1) Priority: 15360255
(16) RELAY IPv6 (2) Priority: 15360254
(17) RELAY IPv4 (1) Priority: 15104255
(18) RELAY IPv4 (2) Priority: 15104254
]]></artwork>
</figure>
The result is an even spread of IPv6 and IPv4 candidates among
the different candidate types (HOST, SRFLX, RELAY). The
local_preference value is calculated separately for each
candidate type.
</t>
<t>
The resulting checklist will depend on the priorities of the
remote candidates. It is not possible to ensure an even spread
of IPv4 and IPv6 addresses unless both the remote and local
sides uses the simple recommendations in this draft. It is worth
noting that there is a good chance it will some effect even
if the remote side does not support this. It will not break
interoperability with other ICE implementations.
</t>
<t>
<cref anchor="Q1" source ="palmarti">Need to take a closer
look at how the unfreezing happens and how this affects the
component id is the sorting above.</cref>
<cref anchor="Q2" source ="palmarti"> The implementations of
the algorithm does not implement pruning of the pairs. So the
checklist is shorter in real life than the example in the appendix.
</cref>
</t>
</section>
<section title="IANA Considerations">
<t>None.</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"/>
apply to this use.</t>
</section>
<section anchor="ack" title="Acknowledgements">
<t>Authors would like to thank Dan Wing, Ari Keranen, Bernard
Aboba, Martin Thomson, Jonathan Lennox and Balint Menyhart for
their comments and review.</t>
</section>
<section title="Implementation Status">
<t>[Note to RFC Editor: Please remove this section and reference to
<xref target="RFC6982"></xref> prior to publication.]</t>
<t>This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in <xref
target="RFC6982"></xref>. The description of implementations in this
section is intended to assist the IETF in its decision processes in
progressing drafts to RFCs. Please note that the listing of any
individual implementation here does not imply endorsement by the IETF.
Furthermore, no effort has been spent to verify the information
presented here that was supplied by IETF contributors. This is not
intended as, and must not be construed to be, a catalog of available
implementations or their features. Readers are advised to note that
other implementations may exist.</t>
<t>According to <xref target="RFC6982"></xref>, "this will allow
reviewers and working groups to assign due consideration to documents
that have the benefit of running code, which may serve as evidence of
valuable experimentation and feedback that have made the implemented
protocols more mature. It is up to the individual working groups to use
this information as they see fit".</t>
<section title="HappyE-ICE-Test">
<t><list style="hanging">
<t hangText="Organization: ">
Private Initiative ([email protected])
</t>
<t hangText="Description: ">
A private initiative to create working code to show how
the recommendations in this draft can be implemented. The
code is publicly available at github.
</t>
<t hangText="Implementation: ">
https://github.com/palerikm/HappyE-ICE-Test
</t>
<t hangText="Level of maturity: ">
The code only implements the parts that cover this draft
and not a full ICE implementation. There is work in
progress to get this into a full implementation,
unfortunately that source code is not at the current
time available to the public. It is currently not
implementing the pruning of the checklist pairs as
described in section 5.7.3 of the ICE RFC.
</t>
<t hangText="Coverage: ">
Implement this draft.
</t>
<t hangText="Licensing: ">BSD</t>
<t hangText="Implementation experience: ">
Fiddly. Please not that the developer also is author of
this draft. The implementation also helped writing parts
of this draft.
</t>
<t hangText="Contact: ">Paal-Erik Martinsen
<[email protected]>.</t>
</list></t>
</section>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include="reference.RFC.2119"?>
<?rfc include="reference.RFC.3484"?>
<?rfc include="reference.RFC.5245"?>
<?rfc include="reference.RFC.6724"?>
<?rfc include="reference.RFC.6982"?>
</references>
<section title="Examples">
<t>
<figure>
<artwork align="left"><![CDATA[
********** Local Candidates (sorted) *********
(1) HOST IPv6 (1) Priority: 2129289471
(2) HOST IPv6 (2) Priority: 2129289470
(3) HOST IPv4 (1) Priority: 2129033471
(4) HOST IPv4 (2) Priority: 2129033470
(5) HOST IPv6 (1) Priority: 2128777471
(6) HOST IPv6 (2) Priority: 2128777470
(7) HOST IPv4 (1) Priority: 2128521471
(8) HOST IPv4 (2) Priority: 2128521470
(9) HOST IPv6 (1) Priority: 2128265471
(10) HOST IPv6 (2) Priority: 2128265470
(11) SRFLX IPv6 (1) Priority: 1693081855
(12) SRFLX IPv6 (2) Priority: 1693081854
(13) SRFLX IPv4 (1) Priority: 1692825855
(14) SRFLX IPv4 (2) Priority: 1692825854
(15) RELAY IPv6 (1) Priority: 15360255
(16) RELAY IPv6 (2) Priority: 15360254
(17) RELAY IPv4 (1) Priority: 15104255
(18) RELAY IPv4 (2) Priority: 15104254
]]></artwork>
</figure>
</t>
<t>
<figure>
<artwork align="left"><![CDATA[
********** Remote Candidates *********
(1) HOST IPv6 (1) Priority: 2129289471
(2) HOST IPv6 (1) Priority: 2129289471
(3) HOST IPv6 (1) Priority: 2129289471
(4) HOST IPv6 (2) Priority: 2129289470
(5) HOST IPv6 (2) Priority: 2129289470
(6) HOST IPv6 (2) Priority: 2129289470
(7) HOST IPv4 (1) Priority: 2129033471
(8) HOST IPv4 (1) Priority: 2129033471
(9) HOST IPv4 (2) Priority: 2129033470
(10) HOST IPv4 (2) Priority: 2129033470
(11) IPv6 (1) Priority: 1693081855
(12) IPv6 (2) Priority: 1693081854
(13) IPv4 (1) Priority: 1692825855
(14) IPv4 (2) Priority: 1692825854
(15) RELAY IPv6 (1) Priority: 15360255
(16) RELAY IPv6 (2) Priority: 15360254
(17) RELAY IPv4 (1) Priority: 15104255
(18) RELAY IPv4 (2) Priority: 15104254
]]></artwork>
</figure>
</t>
<t>
The pairs have not been pruned a described in section 5.7.3 of
the ICE spec.
<figure>
<artwork align="left"><![CDATA[
********** CheckList *********
0 HOST 6(1) 2129289471 HOST 6(1) 2129289471(9145228645920719358)
1 HOST 6(1) 2129289471 HOST 6(1) 2129289471(9145228645920719358)
2 HOST 6(1) 2129289471 HOST 6(1) 2129289471(9145228645920719358)
3 HOST 6(2) 2129289470 HOST 6(2) 2129289470(9145228641625752060)
4 HOST 6(2) 2129289470 HOST 6(2) 2129289470(9145228641625752060)
5 HOST 6(2) 2129289470 HOST 6(2) 2129289470(9145228641625752060)
6 HOST 4(1) 2129033471 HOST 4(1) 2129033471(9144129134292431358)
7 HOST 4(1) 2129033471 HOST 4(1) 2129033471(9144129134292431358)
8 HOST 4(2) 2129033470 HOST 4(2) 2129033470(9144129129997464060)
9 HOST 4(2) 2129033470 HOST 4(2) 2129033470(9144129129997464060)
10 HOST 6(1) 2128777471 HOST 6(1) 2129289471(9143029622665167358)
11 HOST 6(1) 2128777471 HOST 6(1) 2129289471(9143029622665167358)
12 HOST 6(1) 2128777471 HOST 6(1) 2129289471(9143029622665167358)
13 HOST 6(2) 2128777470 HOST 6(2) 2129289470(9143029618370200060)
14 HOST 6(2) 2128777470 HOST 6(2) 2129289470(9143029618370200060)
15 HOST 6(2) 2128777470 HOST 6(2) 2129289470(9143029618370200060)
16 HOST 4(1) 2128521471 HOST 4(1) 2129033471(9141930111036879358)
17 HOST 4(1) 2128521471 HOST 4(1) 2129033471(9141930111036879358)
18 HOST 4(2) 2128521470 HOST 4(2) 2129033470(9141930106741912060)
19 HOST 4(2) 2128521470 HOST 4(2) 2129033470(9141930106741912060)
20 HOST 6(1) 2128265471 HOST 6(1) 2129289471(9140830599409615358)
21 HOST 6(1) 2128265471 HOST 6(1) 2129289471(9140830599409615358)
22 HOST 6(1) 2128265471 HOST 6(1) 2129289471(9140830599409615358)
23 HOST 6(2) 2128265470 HOST 6(2) 2129289470(9140830595114648060)
24 HOST 6(2) 2128265470 HOST 6(2) 2129289470(9140830595114648060)
25 HOST 6(2) 2128265470 HOST 6(2) 2129289470(9140830595114648060)
26 HOST 6(1) 2129289471 SRFLX 6(1) 1693081855(7271731200934593023)
27 SRFLX 6(1) 1693081855 HOST 6(1) 2129289471(7271731200934593022)
28 SRFLX 6(1) 1693081855 HOST 6(1) 2129289471(7271731200934593022)
29 SRFLX 6(1) 1693081855 HOST 6(1) 2129289471(7271731200934593022)
30 HOST 6(1) 2128777471 SRFLX 6(1) 1693081855(7271731200933569023)
31 HOST 6(1) 2128265471 SRFLX 6(1) 1693081855(7271731200932545023)
32 SRFLX 6(1) 1693081855 SRFLX 6(1) 1693081855(7271731200062177790)
33 HOST 6(2) 2129289470 SRFLX 6(2) 1693081854(7271731196639625725)
34 SRFLX 6(2) 1693081854 HOST 6(2) 2129289470(7271731196639625724)
35 SRFLX 6(2) 1693081854 HOST 6(2) 2129289470(7271731196639625724)
36 SRFLX 6(2) 1693081854 HOST 6(2) 2129289470(7271731196639625724)
37 HOST 6(2) 2128777470 SRFLX 6(2) 1693081854(7271731196638601725)
38 HOST 6(2) 2128265470 SRFLX 6(2) 1693081854(7271731196637577725)
39 SRFLX 6(2) 1693081854 SRFLX 6(2) 1693081854(7271731195767210492)
40 HOST 4(1) 2129033471 SRFLX 4(1) 1692825855(7270631689306305023)
41 SRFLX 4(1) 1692825855 HOST 4(1) 2129033471(7270631689306305022)
42 SRFLX 4(1) 1692825855 HOST 4(1) 2129033471(7270631689306305022)
43 HOST 4(1) 2128521471 SRFLX 4(1) 1692825855(7270631689305281023)
44 SRFLX 4(1) 1692825855 SRFLX 4(1) 1692825855(7270631688433889790)
45 HOST 4(2) 2129033470 SRFLX 4(2) 1692825854(7270631685011337725)
46 SRFLX 4(2) 1692825854 HOST 4(2) 2129033470(7270631685011337724)
47 SRFLX 4(2) 1692825854 HOST 4(2) 2129033470(7270631685011337724)
48 HOST 4(2) 2128521470 SRFLX 4(2) 1692825854(7270631685010313725)
49 SRFLX 4(2) 1692825854 SRFLX 4(2) 1692825854(7270631684138922492)
50 HOST 6(1) 2129289471 RELAY 6(1) 15360255 (65971797141799423)
51 RELAY 6(1) 15360255 HOST 6(1) 2129289471(65971797141799422)
52 RELAY 6(1) 15360255 HOST 6(1) 2129289471(65971797141799422)
53 RELAY 6(1) 15360255 HOST 6(1) 2129289471(65971797141799422)
54 HOST 6(1) 2128777471 RELAY 6(1) 15360255 (65971797140775423)
55 HOST 6(1) 2128265471 RELAY 6(1) 15360255 (65971797139751423)
56 SRFLX 6(1) 1693081855 RELAY 6(1) 15360255 (65971796269384191)
57 RELAY 6(1) 15360255 SRFLX 6(1) 1693081855(65971796269384190)
58 RELAY 6(1) 15360255 RELAY 6(1) 15360255 (65971792913940990)
59 HOST 6(2) 2129289470 RELAY 6(2) 15360254 (65971792846832125)
60 RELAY 6(2) 15360254 HOST 6(2) 2129289470(65971792846832124)
61 RELAY 6(2) 15360254 HOST 6(2) 2129289470(65971792846832124)
62 RELAY 6(2) 15360254 HOST 6(2) 2129289470(65971792846832124)
63 HOST 6(2) 2128777470 RELAY 6(2) 15360254 (65971792845808125)
64 HOST 6(2) 2128265470 RELAY 6(2) 15360254 (65971792844784125)
65 SRFLX 6(2) 1693081854 RELAY 6(2) 15360254 (65971791974416893)
66 RELAY 6(2) 15360254 SRFLX 6(2) 1693081854(65971791974416892)
67 RELAY 6(2) 15360254 RELAY 6(2) 15360254 (65971788618973692)
68 HOST 4(1) 2129033471 RELAY 4(1) 15104255 (64872285513511423)
69 RELAY 4(1) 15104255 HOST 4(1) 2129033471(64872285513511422)
70 RELAY 4(1) 15104255 HOST 4(1) 2129033471(64872285513511422)
71 HOST 4(1) 2128521471 RELAY 4(1) 15104255 (64872285512487423)
72 SRFLX 4(1) 1692825855 RELAY 4(1) 15104255 (64872284641096191)
73 RELAY 4(1) 15104255 SRFLX 4(1) 1692825855(64872284641096190)
74 RELAY 4(1) 15104255 RELAY 4(1) 15104255 (64872281285652990)
75 HOST 4(2) 2129033470 RELAY 4(2) 15104254 (64872281218544125)
76 RELAY 4(2) 15104254 HOST 4(2) 2129033470(64872281218544124)
77 RELAY 4(2) 15104254 HOST 4(2) 2129033470(64872281218544124)
78 HOST 4(2) 2128521470 RELAY 4(2) 15104254 (64872281217520125)
79 SRFLX 4(2) 1692825854 RELAY 4(2) 15104254 (64872280346128893)
80 RELAY 4(2) 15104254 SRFLX 4(2) 1692825854(64872280346128892)
81 RELAY 4(2) 15104254 RELAY 4(2) 15104254 (64872276990685692)
]]></artwork>
</figure>
</t>
</section>
</back>
</rfc>