Internet DRAFT - draft-ietf-mmusic-ice-dualstack-fairness
draft-ietf-mmusic-ice-dualstack-fairness
MMUSIC P. Martinsen
Internet-Draft T. Reddy
Intended status: Informational P. Patil
Expires: March 10, 2016 Cisco
September 7, 2015
ICE Multihomed and IPv4/IPv6 Dual Stack Fairness
draft-ietf-mmusic-ice-dualstack-fairness-02
Abstract
This document provides guidelines on how to make Interactive
Connectivity Establishment (ICE) conclude faster in multihomed and
IPv4/IPv6 dual-stack scenarios where broken paths exist. The
provided guidelines are backwards compatible with the original ICE
specification.
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 March 10, 2016.
Copyright Notice
Copyright (c) 2015 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
include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Notational Conventions . . . . . . . . . . . . . . . . . . . 3
3. Improving ICE Multihomed Fairness . . . . . . . . . . . . . . 3
4. Improving ICE Dual Stack Fairness . . . . . . . . . . . . . . 4
5. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Implementation Status . . . . . . . . . . . . . . . . . . . . 7
7.1. ICE-Dual Starck Fairness Test code . . . . . . . . . . . 8
7.2. ICE-Dual Starck Fairness Test code . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 8
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
10.1. Normative References . . . . . . . . . . . . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
Applications should take special care to deprioritize network
interfaces known to provide unreliable connectivity when operating in
a multihomed environment. For example certain tunnel services might
provide unreliable connectivity. Doing so will ensure a more fair
distribution of the connectivity checks across available network
interfaces on the device. The simple guidelines presented here
describes how to deprioritize interfaces known by the application to
provide unreliable connectivity.
There is a also a need to introduce more fairness when handling
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, reflexive or relay) are sent such
that an IP address family is completely depleted before checks from
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 or excessive slow, this specification encourages intermingling
the different address families when connectivity checks are
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performed. 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.
This document describes how to fairly order the candidates in
multihomed and dual-stack environments, thus affecting the sending
order of the connectivity checks. If aggressive nomination is in
use, this will have an effect on what candidate pair ends up as the
active one. Ultimately it should be up to the agent to decide what
candidate pair is best suited for transporting media.
The guidelines outlined in this specification are backward compatible
with a standard ICE implementation. This specification only alters
the values used to create the resulting checklists in such a way that
the core mechanisms from ICE [RFC5245] are still in effect. The
introduced fairness might be better, but not worse than what exists
today.
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 Multihomed Fairness
A multihomed ICE agent can potentially send and receive connectivity
checks on all available interfaces and IP addresses. It is possible
for an interface to have several IP addresses associated with it. To
avoid unnecessary delay when performing connectivity checks it would
be beneficial to prioritize interfaces and IP addresses known by the
agent to provide stable connectivity. If the agent have access to
information about the physical network it is connected to (Like SSID
in a WiFi Network) this can be used as information regarding how that
network interface should be prioritized at this point in time.
The application knowledge regarding the reliability of an interface
can also be based on simple metrics like previous connection success/
failure rates or a more static model based on interface types like
wired, wireless, cellular, virtual, tunneled and so on.
Candidates from a interface known to the application to provide
unreliable connectivity SHOULD get a low candidate priority. This
ensures they appear near the end of the candidate list, and would be
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the last to be tested during the connectivity check phase. This
allows candidate pairs more likely to succeed to be tested first.
If the application is unable to get any interface information
regarding type or unable to store any relevant metrics, it SHOULD
treat all interfaces as if they have reliable connectivity. This
ensures all interfaces gets their fair chance to perform their
connectivity checks.
4. 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
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. However, 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 [RFC5245] section 4.1.2.1.
Implementations SHOULD prioritize IPv6 candidates by putting some of
them first in the the intermingled checklist. This increases the
chance of a IPv6 connectivity checks to complete first and be ready
for nomination or usage. This enables implementations to follow the
intent of [RFC6555] "Happy Eyeballs: Success with Dual-Stack Hosts".
It is worth noting that the timing recommendations in [RFC6555] are
to excessive for ICE usage.
5. 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)
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ICE [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 local preference value for IPv4 and IPv6 addresses,
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. It is also possible to assign lower
priorities to IP addresses derived from unreliable interfaces using
the local preference value.
It is worth mentioning that [RFC5245] section 4.1.2 say that; "if
there are multiple candidates for a particular component for a
particular media stream that have the same type, the local preference
MUST be unique for each one".
The local type preference can be dynamically changed in such a way
that IPv4 and IPv6 address candidates end up intermingled regardless
of candidate type. This is useful if there are a lot of IPv6 host
candidates effectively blocking connectivity checks for IPv4 server
reflexive candidates.
Candidates with IP addresses from a unreliable interface SHOULD be
ordered at the end of the checklist. Not intermingled as the dual-
stack candidates.
The list below shows a sorted local candidate list where the priority
is calculated in such a way that the IPv4 and IPv6 candidates are
intermingled (No multihomed candidates). To allow for earlier
connectivity checks for the IPv4 server reflexive candidates, some of
the IPv6 host candidates are demoted. This is just an example of how
a candidate priorities can be calculated to provide better fairness
between IPv4 and IPv6 candidates without breaking any of the ICE
connectivity checks.
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Candidate Address Component
Type Type ID Priority
-------------------------------------------
(1) HOST IPv6 (1) 2129289471
(2) HOST IPv6 (2) 2129289470
(3) HOST IPv4 (1) 2129033471
(4) HOST IPv4 (2) 2129033470
(5) HOST IPv6 (1) 2128777471
(6) HOST IPv6 (2) 2128777470
(7) HOST IPv4 (1) 2128521471
(8) HOST IPv4 (2) 2128521470
(9) HOST IPv6 (1) 2127753471
(10) HOST IPv6 (2) 2127753470
(11) SRFLX IPv6 (1) 1693081855
(12) SRFLX IPv6 (2) 1693081854
(13) SRFLX IPv4 (1) 1692825855
(14) SRFLX IPv4 (2) 1692825854
(15) HOST IPv6 (1) 1692057855
(16) HOST IPv6 (2) 1692057854
(17) RELAY IPv6 (1) 15360255
(18) RELAY IPv6 (2) 15360254
(19) RELAY IPv4 (1) 15104255
(20) RELAY IPv4 (2) 15104254
SRFLX = server reflexive
Note that the list does not alter the component ID part of the
formula. This keeps the different components (RTP and RTCP) close in
the list. What matters is the ordering of the candidates with
component ID 1. Once the checklist is formed for a media stream the
candidate pair with component ID 1 will be tested first. If ICE
connectivity check is successful then other candidate pairs with the
same foundation will be unfrozen ([RFC5245] section 5.7.4. Computing
States).
The local and remote agent can have different algorithms for choosing
the local preference and type preference values without impacting the
synchronization between the local and remote check lists.
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)
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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.
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.
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. The resulting local and remote checklist will still
be synchronized. The introduced fairness might be better, but not
worse than what exists today
If aggressive nomination is in use the procedures described in this
document might change what candidate pair ends up as the active one.
A test implementation with an example algorithm is available
[ICE_dualstack_imp].
6. IANA Considerations
None.
7. Implementation Status
[Note to RFC Editor: Please remove this section and reference to
[RFC6982] prior to publication.]
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 [RFC6982].
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.
According to [RFC6982], "this will allow reviewers and working groups
to assign due consideration to documents that have the benefit of
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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".
7.1. ICE-Dual Starck Fairness Test code
Organization: Cisco
Description: Open-Source ICE, TURN and STUN implementation.
Implementation: https://github.com/palerikm/ICE-DualStackFairness
Level of maturity: Code is stable. Tests
Coverage: Follows the recommendations in this document
Licensing: BSD
Implementation experience: Straightforward as there are no
compatibility issues.
Contact: Paal-Erik Martinsen palmarti@cisco.com
7.2. ICE-Dual Starck Fairness Test code
Organization: Others
Description: Major ICE implementations, browser based and stand-
alone ICE, TURN and STUN implementations.
Implementation: Product specific.
Level of maturity: Code is stable and available in the wild.
Coverage: Implements the recommendations in this document.
Licensing: Some open source, some close source
Implementation experience: Already implemented in some of the
implementations. This documents describes what needs to be done
to achieve the desired fairness.
8. Security Considerations
STUN connectivity check using MAC computed during key exchanged in
the signaling channel provides message integrity and data origin
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authentication as described in section 2.5 of [RFC5245] apply to this
use.
9. Acknowledgements
Authors would like to thank Dan Wing, Ari Keranen, Bernard Aboba,
Martin Thomson, Jonathan Lennox, Balint Menyhart, Ole Troan and Simon
Perreault for their comments and review.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3484] Draves, R., "Default Address Selection for Internet
Protocol version 6 (IPv6)", RFC 3484, DOI 10.17487/
RFC3484, February 2003,
<http://www.rfc-editor.org/info/rfc3484>.
[RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
(ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols", RFC 5245, DOI
10.17487/RFC5245, April 2010,
<http://www.rfc-editor.org/info/rfc5245>.
[RFC6555] Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with
Dual-Stack Hosts", RFC 6555, DOI 10.17487/RFC6555, April
2012, <http://www.rfc-editor.org/info/rfc6555>.
[RFC6724] Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown,
"Default Address Selection for Internet Protocol Version 6
(IPv6)", RFC 6724, DOI 10.17487/RFC6724, September 2012,
<http://www.rfc-editor.org/info/rfc6724>.
[RFC6982] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", RFC 6982, DOI
10.17487/RFC6982, July 2013,
<http://www.rfc-editor.org/info/rfc6982>.
10.2. Informative References
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[ICE_dualstack_imp]
Martinsen, P., "ICE DualStack Test Implementation github
repo", <https://github.com/palerikm/ICE-
DualStackFairness>.
Authors' Addresses
Paal-Erik Martinsen
Cisco Systems, Inc.
Philip Pedersens Vei 22
Lysaker, Akershus 1325
Norway
Email: palmarti@cisco.com
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
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