wdiff rfc8421.original rfc8421.txt

ICE
Internet Engineering Task Force (IETF) P. Martinsen
Internet-Draft
Request for Comments: 8421 Cisco
BCP: 217 T. Reddy
Intended status:
Category: Best Current Practice McAfee, Inc.
ISSN: 2070-1721 P. Patil
Expires: May 18, 2017
Cisco
November 14, 2016

ICE
July 2018

Guidelines for Multihomed and IPv4/IPv6 Dual Stack Guidelines
draft-ietf-ice-dualstack-fairness-07 Dual-Stack Interactive
Connectivity Establishment (ICE)

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 backward compatible with the original ICE
specification.
specification (see RFC 5245).

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 memo documents an Internet Best Current Practice.

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

Internet-Drafts are draft documents valid the IETF community. It has
received public review and has been approved for a maximum publication by the
Internet Engineering Steering Group (IESG). Further information on
BCPs is available in Section 2 of six months RFC 7841.

Information about the current status of this document, any errata,
and how to provide feedback on it may be updated, replaced, or obsoleted by other documents obtained 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 May 18, 2017.
https://www.rfc-editor.org/info/rfc8421.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info)
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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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. ICE Multihomed Recomendations . Recommendations . . . . . . . . . . . . . . . 3
4. ICE Dual Stack Recomendations . Dual-Stack Recommendations . . . . . . . . . . . . . . . 4
5. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Implementation Status . Security Considerations . . . . . . . . . . . . . . . . . . . 7
7.1. ICE-Dual Stack Fairness Test code . . . . . . . . . . . . 8
7.2. ICE-Dual Stack Fairness Test code . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . References . . . 9
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
10. 7
8.1. Normative References . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . 9
10.1. Normative References . . . . . . . . . . . 8
Acknowledgements . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . 10 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 8

1. Introduction

In multihomed and IPv4/IPv6 dual-stack environments environments, ICE
[I-D.ietf-ice-rfc5245bis] [RFC8445]
would benefit by a fair distribution of its connectivity checks
across available interfaces or IP address types. With a fair
distribution of the connectivity checks, excessive delays are avoided
if a particular network path is broken or slow. It Arguably, it would
arguably
be better to put the interfaces or address types known to the
application last in the checklist. However, the main motivation by
ICE is to make no assumptions regarding network topology, hence topology; hence, a
fair distribution of the connectivity checks is more appropriate. If
an application operates in a well-known environment is environment, it can safely
override the recommendation given in this document.

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
describe how to deprioritize interfaces known by the application to
provide unreliable connectivity.

There is also a need to introduce better handling of connectivity
checks for different IP address families in dual-stack IPv4/IPv6 ICE
scenarios. Following the recommendations from RFC6724 RFC 6724 [RFC6724]
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 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 user-noticeable delays with
setup if the path for the prioritized address family is broken.

To avoid user noticeable user-noticeable delays when either the IPv6 or IPv4 path is
broken or excessively slow, this specification encourages
intermingling the different address families when connectivity checks
are performed. This 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. Further Further, this document recommends to keep keeping
track of previous known connectivity problem problems and assign assigning a lower
priority to those addresses. Specific mechanisms and rules for
tracking connectivity issues are out of scope for this document.

This document describes what parameters an agent can safely alter to
fairly order the checklist candidate pairs in multihomed and dual-
stack environments, thus affecting the sending order of the
connectivity checks. Actual The actual values of those parameters is are an
implementation detail. Dependant Dependent on the nomination method in use,
this might have an effect on what candidate pair ends up as the
active one. Ultimately 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 the original ICE implementation. This specification only alters
the values used to create the resulting checklists in such a way that
the core mechanisms from the original ICE specification [RFC5245] and ICEbis
[I-D.ietf-ice-rfc5245bis]
its replacement [RFC8445] are still in effect.

2. Notational Conventions

This document uses terminology defined in [I-D.ietf-ice-rfc5245bis]. [RFC8445].

3. ICE Multihomed Recomendations Recommendations

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 checks, it would
be beneficial to prioritize interfaces and IP addresses known by the
agent to provide stable connectivity.

The application knowledge regarding the reliability of an interface
can also be based on simple metrics like previous connection success/
failure rates rates, or it can be a more static model based on interface
types like wired, wireless, cellular, virtual, and tunneled in
conjunction with other operational metrics. This would require the
application to have the right permissions to obtain such operational
metrics.

Candidates from an interface known to the application to provide
unreliable connectivity should get a low candidate priority. When to
consider connectivity as unreliable is implementation specific.
Usage of ICE is not limited to VoIP Voice over IP (VoIP) applications.
What an application sees as unreliability might be determined by a
mix of how long lived the connection is, how often setup is required required,
and others, other, for now unknown, requirements. This is purely an
optimization to speed up the ICE connectivity check phase.

If the application is unable to get any interface information
regarding type or is unable to store any relevant metrics, it should
treat all interfaces as if they have reliable connectivity. This
ensures that all interfaces gets their get a fair chance to perform their
connectivity checks.

4. ICE Dual Stack Recomendations Dual-Stack Recommendations

Candidates should be prioritized such that a sequence of candidates
belonging to the same address family will be intermingled with
candidates from an alternate IP family. For family, for example, promoting promote 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 (i.e., reorder candidates such that both IPv6 and IPv4
candidates get a fair chance during the connectivity check phase. phase).
This makes ICE connectivity checks more responsive to broken path broken-path
failures of an address family.

An ICE agent can choose select an algorithm or a technique of its choice to
ensure that the resulting check lists checklists have a fair intermingled mix of
IPv4 and IPv6 address families. However, modifying the check list checklist
directly can lead to uncoordinated local and remote check lists checklists that
result in ICE taking longer to complete or or, in the worst case scenario
scenario, fail. The best approach is to set the appropriate value
for local preference in the formula for calculating the candidate
priority value as described in ICE [I-D.ietf-ice-rfc5245bis] the "Recommended Formula" section "4.1.2.1
Recommended Formula".
(Section 5.1.2.1) of [RFC8445].

Implementations should prioritize IPv6 candidates by putting some of
them first in the intermingled checklist. This increases the chance
of 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". Hosts" [RFC8305].
It is worth noting that the timing recommendations in [RFC6555] [RFC8305] will
be overruled by how ICE paces out its connectivity checks.

A simple formula to calculate how many IPv6 addresses to put before
any IPv4 addresses could look like:

Hi = (N_4 + N_6) / N_4

Where Hi = Head start before intermingling starts
N_4 = Number of IPv4 addresses
N_6 = Number of IPv6 addresses

If a host have 2 has two IPv4 addresses and 6 six IPv6 addresses, it will
insert an IP4 IPv4 address after 4 four IPv6 addresses by choosing the
appropriate local preference values when calculating the pair
priorities.

5. Compatibility

ICE [I-D.ietf-ice-rfc5245bis] section "4.1.2 Prioritizing Candidates"
states that the

The formula in section "4.1.2.1 Recommended Formula"
should Section 5.1.2 of [RFC8445] 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 [I-D.ietf-ice-rfc5245bis] section "4.1.2.2 Guidelines

"Guidelines for Choosing Type and Local Preferences" (Section 5.1.2.2
of [RFC8445]) 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 end 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 [I-D.ietf-ice-rfc5245bis] section
"4.1.2.1 Recommended Formula" says that; Section 5.1.2.1 of [RFC8445] states that
"if there are multiple candidates for a particular component for a
particular media stream that has 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 an unreliable interface should be
ordered at the end of the checklist, i.e., 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 (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.

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) the Real-time
Transport Control Protocol (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 stream, the candidate pair with
component ID 1 will be tested first. If the ICE connectivity check
is successful successful, then other candidate pairs with the same foundation
will be unfrozen ([I-D.ietf-ice-rfc5245bis] section
5.1.3.4. Computing States). (see "Computing Candidate Pair States" in
Section 6.1.2.6 of [RFC8445]).

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. checklists.

The check list checklist is made up of candidate pairs. A candidate pair is two
candidates paired up and given a candidate pair priority as described
in [I-D.ietf-ice-rfc5245bis] section 5.1.3.2. Section 6.1.2.3 of [RFC8445]. Using the pair priority formula:

pair priority = 2^32*MIN(G,D) + 2*MAX(G,D) + (G>D?1:0)

Where G is the candidate priority provided by the controlling agent agent,
and D is the candidate priority provided by the controlled agent.
This ensures that the local and remote check lists checklists 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. cautiously, i.e., lower IPv4
candidate priority values compared to the other agent, will influence
the check
list checklist the most due to (2^32*MIN(G,D)) in the formula.

These recommendations are backward compatible with a standard the original ICE
implementation. The resulting local and remote checklist will still
be synchronized.

Dependant

Dependent of the nomination method in use use, the procedures described
in this document might change what candidate pair ends up as the
active one.

A test implementation of an example algorithm is available at
[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
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 Stack 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.

Coverage: Follows the recommendations in this document

Licensing: BSD

Implementation experience: Straightforward as there are has no
compatibility issues.

Contact: Paal-Erik Martinsen palmarti@cisco.com

7.2. ICE-Dual Stack 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 document describes what needs to be done to
achieve the desired fairness.

8. IANA actions.

7. Security Considerations

The security considerations described in [I-D.ietf-ice-rfc5245bis] [RFC8445] are still valid. It
changes recommended values and describes how an agent could choose
those values in a safe way. In section Section 3 3, the agent can prioritize
the network interface based on previous network knowledge. This can
potentially be unwanted information leakage towards the remote agent.

9. Acknowledgements

Authors would like to thank Dan Wing, Ari Keranen, Bernard Aboba,
Martin Thomson, Jonathan Lennox, Balint Menyhart, Ole Troan, Simon
Perreault, Ben Cambell and Mirja Kuehlewind for their comments and
review.

10.

8. References

10.1.

8.1. Normative References

[I-D.ietf-ice-rfc5245bis]
Keranen, A., Holmberg, C., and J. Rosenberg, "Interactive
Connectivity Establishment (ICE): A Protocol for Network
Address Translator (NAT) Traversal", draft-ietf-ice-
rfc5245bis-05 (work in progress), October 2016.

[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>.
<https://www.rfc-editor.org/info/rfc5245>.

[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",
<https://www.rfc-editor.org/info/rfc6724>.

[RFC8305] Schinazi, D. and T. Pauly, "Happy Eyeballs Version 2:
Better Connectivity Using Concurrency", RFC 6982, 8305,
DOI
10.17487/RFC6982, 10.17487/RFC8305, December 2017,
<https://www.rfc-editor.org/info/rfc8305>.

[RFC8445] Keranen, A., Holmberg, C., and J. Rosenberg, "Interactive
Connectivity Establishment (ICE): A Protocol for Network
Address Translator (NAT) Traversal", RFC 8445,
DOI 10.17487/RFC8445, July 2013,
<http://www.rfc-editor.org/info/rfc6982>.

10.2. 2018,
<https://www.rfc-editor.org/info/rfc8445>.

8.2. Informative References

[ICE_dualstack_imp]
Martinsen, P.,
"ICE DualStack Happy Eyeball Test Implementation github
repo", <https://github.com/palerikm/ICE-
DualStackFairness>. Algorithms", commit 45083fb,
January 2014,
<https://github.com/palerikm/ICE-DualStackFairness>.

Acknowledgements

The authors would like to thank Dan Wing, Ari Keranen, Bernard Aboba,
Martin Thomson, Jonathan Lennox, Balint Menyhart, Ole Troan, Simon
Perreault, Ben Campbell, and Mirja Kuehlewind for their comments and
review.

Authors' Addresses

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

Email: palmarti@cisco.com
Tirumaleswar Reddy
Cisco Systems,
McAfee, Inc.
Cessna
Embassy Golf Link Business Park, Varthur Hobli
Sarjapur Marathalli Outer Ring Road Park
Bangalore, Karnataka 560103 560071
India

Email: tireddy@cisco.com TirumaleswarReddy_Konda@McAfee.com

Prashanth Patil
Cisco Systems, Inc.
Bangalore
India

Email: praspati@cisco.com