Interactive Connectivity Establishment Patiently Awaiting Connectivity (ICE PAC)
RFC 8863

Document Type RFC - Proposed Standard (January 2021; No errata)
Updates RFC 8445, RFC 8838
Authors Christer Holmberg  , Justin Uberti 
Last updated 2021-01-18
Replaces draft-holmberg-ice-pac
Stream Internent Engineering Task Force (IETF)
Formats plain text html xml pdf htmlized (tools) htmlized bibtex
Stream WG state Submitted to IESG for Publication
Document shepherd Nils Ohlmeier
Shepherd write-up Show (last changed 2019-10-15)
IESG IESG state RFC 8863 (Proposed Standard)
Action Holders
Consensus Boilerplate Yes
Telechat date
Responsible AD Murray Kucherawy
Send notices to Nils Ohlmeier <>
IANA IANA review state Version Changed - Review Needed
IANA action state No IANA Actions

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
                               (ICE PAC)


   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 Notice

   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
   ( 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

   1.  Introduction
   2.  Conventions
   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
   Authors' Addresses

1.  Introduction

   [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.

2.  Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "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
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