Interactive Connectivity Establishment Patiently Awaiting Connectivity (ICE PAC)
Internet Engineering Task Force (IETF) C. Holmberg
Request for Comments: 8863 Ericsson
Updates: 8445, 8838 J. Uberti
Category: Standards Track Google
ISSN: 2070-1721 January 2021
Interactive Connectivity Establishment Patiently Awaiting Connectivity
During the process of establishing peer-to-peer connectivity,
Interactive Connectivity Establishment (ICE) agents can encounter
situations where they have no candidate pairs to check, and, as a
result, conclude that ICE processing has failed. However, because
additional candidate pairs can be discovered during ICE processing,
declaring failure at this point may be premature. This document
discusses when these situations can occur.
This document updates RFCs 8445 and 8838 by requiring that an ICE
agent wait a minimum amount of time before declaring ICE failure,
even if there are no candidate pairs left to check.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
Copyright (c) 2021 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
(https://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
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
3. Relevant Scenarios
3.1. No Candidates from Peer
3.2. All Candidates Discarded
3.3. Immediate Candidate Pair Failure
4. Update to RFC 8445
5. Update to RFC 8838
6. Security Considerations
7. IANA Considerations
8. Normative References
[RFC8445] describes a protocol, Interactive Connectivity
Establishment (ICE), for Network Address Translator (NAT) traversal
for UDP-based communication.
When using ICE, endpoints will typically exchange ICE candidates,
form a list of candidate pairs, and then test each candidate pair to
see if connectivity can be established. If the test for a given pair
fails, it is marked accordingly, and if all pairs have failed, the
overall ICE process typically is considered to have failed.
During the process of connectivity checks, additional candidates may
be created as a result of successful inbound checks from the remote
peer. Such candidates are referred to as peer-reflexive candidates;
once discovered, these candidates will be used to form new candidate
pairs, which will be tested like any other. However, there is an
inherent problem here; if, before learning about any peer-reflexive
candidates, an endpoint runs out of candidate pairs to check, either
because it has none or it considers them all to have failed, it will
prematurely declare failure and terminate ICE processing. This
problem can occur in many common situations.
This specification updates [RFC8445] and [RFC8838] by simply
requiring that an ICE agent wait a minimum amount of time before
declaring ICE failure, even if there are no candidate pairs to check
or all candidate pairs have failed. This delay provides enough time
for the discovery of peer-reflexive candidates, which may eventually
lead to ICE processing completing successfully.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Relevant Scenarios
As noted above, the core problem this specification attempts to
address is the situation where even after local gathering and remote
candidate signaling have completed, the ICE agent immediately ends up
with no valid pairs and no candidate pairs left to check, resulting
Show full document text