Network Working Group P. Thatcher
Internet-Draft H. Zhang
Intended status: Standards Track T. Brandstetter
Expires: January 2, 2017 Google
July 1, 2016

ICE Candidate Removal: Remove ICE candidates when they are no longer useful.


This document describes an extension to the Interactive Connectivity Establishment (ICE) that enables ICE agents to signal the removal of ICE candidates to the remote ICE agent to prevent the remote ICE agent from wasting resources by attempting to use the ICE candidate.

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Table of Contents

1. Introduction

In certain network conditions, ICE agents may find that a local ICE candidate is no longer useful and that the remote ICE agent should not attempt to use that ICE candidate.

For example, if an ICE agent is gathering TURN candidates and finds a set of better candidates (such as using UDP to the TURN server) than candidates already signaled (such as using TCP to the TURN server), it may choose to deallocate the worse candidates. But if it does so, the remote ICE agent may waste time and resources attempting to use the deallocated TURN candidates.

Just as trickle-ice optimizes ICE by signaling the addition of an ICE candidate, this extension optimizes further by signaling the removal of an ICE candidate.

2. Terminology

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 specification makes use of all terminology defined by the protocol for Interactive Connectivity Establishment in [RFC5245].

Removal Signal
The messsage signaled between ICE agents that a candidate is removed.
Removed Candidate
An ICE candiate for which a removal signal is sent.
Removing Agent
The ICE agent that sends the removal signal.
Receiving Agent
The ICE agent that receives the removal signal.

3. Signaling candidate removal

This specification does not define the usage of candidate removal with any specific signaling protocol.

However, it will be noted that any signaling protocol must be able to unique identify the Removed Candidates. For example, a combination of the component, ip address, protocol (UDP or TCP), and port would unique identify a Removed Candidate.

4. Removing candidates when a removal is signaled

When a removal signal, the Receiving Agent MUST NOT pair the Removed Candiates with any future candidates gathered by the Receiving Agent. The Receiving Agent MAY keep the existing candidate pairs that use the Removed Candidates and behave as though the Removed Candidates had not been removed for those candidate pairs.

Why would an Receiving Agent choose not to immediately remove existing candidate pairs? Because the Removing Agent MAY choose to keep the Removed Candidate capable of receiving ICE checks and sending responses so that any ICE checks already sent by the Receiving Agent may continue to work briefly so that media can flow as quickly as possible, even if over a candidate pair that will soon be discarded.

Both the Removing Agent and the Receiving Agent SHOULD prioritize candidate pairs with a Removed Candidate lower than those without a Removed Candidate.

5. IANA Considerations

This specification requests no actions from IANA.

6. Security Considerations


7. Acknowledgements


8. 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.
[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.

Authors' Addresses

Peter Thatcher Google 747 6th St S Kirkland, WA 98033 USA EMail:
Honghai Zhang Google 747 6th St S Kirkland, WA 98033 USA EMail:
Taylor Brandstetter Google 747 6th St S Kirkland, WA 98033 USA EMail: