Trickle ICE: Incremental Provisioning of Candidates for the Interactive Connectivity Establishment (ICE) Protocol
draft-ietf-ice-trickle-19
The information below is for an old version of the document.
| Document | Type | Active Internet-Draft (ice WG) | |
|---|---|---|---|
| Authors | Emil Ivov , Eric Rescorla , Justin Uberti , Peter Saint-Andre | ||
| Last updated | 2018-04-05 | ||
| Replaces | draft-ietf-mmusic-trickle-ice | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Formats | plain text xml htmlized pdfized bibtex | ||
| Reviews |
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||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Nils Ohlmeier | ||
| Shepherd write-up | Show Last changed 2018-01-24 | ||
| IESG | IESG state | IESG Evaluation::Revised I-D Needed | |
| Consensus boilerplate | Yes | ||
| Telechat date |
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Needs a YES. Needs 10 more YES or NO OBJECTION positions to pass. |
||
| Responsible AD | Ben Campbell | ||
| Send notices to | Nils Ohlmeier <nohlmeier@mozilla.com> | ||
| IANA | IANA review state | Version Changed - Review Needed |
draft-ietf-ice-trickle-19
Network Working Group E. Ivov
Internet-Draft Atlassian
Intended status: Standards Track E. Rescorla
Expires: October 7, 2018 RTFM, Inc.
J. Uberti
Google
P. Saint-Andre
Mozilla
April 5, 2018
Trickle ICE: Incremental Provisioning of Candidates for the Interactive
Connectivity Establishment (ICE) Protocol
draft-ietf-ice-trickle-19
Abstract
This document describes "Trickle ICE", an extension to the
Interactive Connectivity Establishment (ICE) protocol that enables
ICE agents to begin connectivity checks while they are still
gathering candidates, by incrementally "trickling" candidates over
time. This method can considerably accelerate the process of
establishing a communication session.
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 https://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 October 7, 2018.
Copyright Notice
Copyright (c) 2018 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
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(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
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Determining Support for Trickle ICE . . . . . . . . . . . . . 5
4. Conveying the Initial ICE Description . . . . . . . . . . . . 6
5. Responder Procedures . . . . . . . . . . . . . . . . . . . . 7
5.1. Conveying the Initial Response . . . . . . . . . . . . . 7
6. Initiator Procedures . . . . . . . . . . . . . . . . . . . . 8
7. Performing Connectivity Checks . . . . . . . . . . . . . . . 8
7.1. Forming Check Lists and Beginning Connectivity
Checks . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.2. Scheduling Checks . . . . . . . . . . . . . . . . . . . . 8
7.3. Empty Check Lists . . . . . . . . . . . . . . . . . . . . 9
7.4. Setting Check List State to Failed . . . . . . . . . . . 9
8. Discovering and Conveying Additional Local Candidates . . . . 9
8.1. Pairing Newly Learned Candidates and Updating
Check Lists . . . . . . . . . . . . . . . . . . . . . . . 11
8.1.1. Inserting a New Pair in a Check List . . . . . . . . 11
8.2. Announcing End of Candidates . . . . . . . . . . . . . . 15
9. Receiving Additional Remote Candidates . . . . . . . . . . . 17
10. Receiving an End-Of-Candidates Indication . . . . . . . . . . 17
11. Subsequent Exchanges and ICE Restarts . . . . . . . . . . . . 17
12. Half Trickle . . . . . . . . . . . . . . . . . . . . . . . . 17
13. Trickle ICE and Peer Reflexive Candidates . . . . . . . . . . 19
14. Requirements for Using Protocols . . . . . . . . . . . . . . 19
15. Preserving Candidate Order while Trickling . . . . . . . . . 19
16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
17. Security Considerations . . . . . . . . . . . . . . . . . . . 21
18. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 21
19. References . . . . . . . . . . . . . . . . . . . . . . . . . 21
19.1. Normative References . . . . . . . . . . . . . . . . . . 21
19.2. Informative References . . . . . . . . . . . . . . . . . 22
Appendix A. Interaction with Regular ICE . . . . . . . . . . . . 23
Appendix B. Interaction with ICE Lite . . . . . . . . . . . . . 24
Appendix C. Changes from Earlier Versions . . . . . . . . . . . 25
C.1. Changes from draft-ietf-ice-trickle-18 . . . . . . . . . 26
C.2. Changes from draft-ietf-ice-trickle-17 . . . . . . . . . 26
C.3. Changes from draft-ietf-ice-trickle-16 . . . . . . . . . 26
C.4. Changes from draft-ietf-ice-trickle-15 . . . . . . . . . 26
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C.5. Changes from draft-ietf-ice-trickle-14 . . . . . . . . . 26
C.6. Changes from draft-ietf-ice-trickle-13 . . . . . . . . . 26
C.7. Changes from draft-ietf-ice-trickle-12 . . . . . . . . . 27
C.8. Changes from draft-ietf-ice-trickle-11 . . . . . . . . . 27
C.9. Changes from draft-ietf-ice-trickle-10 . . . . . . . . . 27
C.10. Changes from draft-ietf-ice-trickle-09 . . . . . . . . . 27
C.11. Changes from draft-ietf-ice-trickle-08 . . . . . . . . . 27
C.12. Changes from draft-ietf-ice-trickle-07 . . . . . . . . . 27
C.13. Changes from draft-ietf-ice-trickle-06 . . . . . . . . . 27
C.14. Changes from draft-ietf-ice-trickle-05 . . . . . . . . . 28
C.15. Changes from draft-ietf-ice-trickle-04 . . . . . . . . . 28
C.16. Changes from draft-ietf-ice-trickle-03 . . . . . . . . . 28
C.17. Changes from draft-ietf-ice-trickle-02 . . . . . . . . . 28
C.18. Changes from draft-ietf-ice-trickle-01 . . . . . . . . . 28
C.19. Changes from draft-ietf-ice-trickle-00 . . . . . . . . . 28
C.20. Changes from draft-mmusic-trickle-ice-02 . . . . . . . . 29
C.21. Changes from draft-ivov-01 and draft-mmusic-00 . . . . . 29
C.22. Changes from draft-ivov-00 . . . . . . . . . . . . . . . 29
C.23. Changes from draft-rescorla-01 . . . . . . . . . . . . . 30
C.24. Changes from draft-rescorla-00 . . . . . . . . . . . . . 31
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 31
1. Introduction
The Interactive Connectivity Establishment (ICE) protocol
[rfc5245bis] describes how an ICE agent gathers candidates, exchanges
candidates with a peer ICE agent, and creates candidate pairs. Once
the pairs have been created, the ICE agent will perform connectivity
checks, and eventually nominate and select pairs that will be used
for sending and receiving data within a communication session.
Following the procedures in [rfc5245bis] can lead to somewhat lengthy
session establishment times, because candidate gathering often
involves querying STUN servers [RFC5389] and allocating relayed
candidates using TURN servers [RFC5766]. Although many ICE
procedures can be completed in parallel, the pacing requirements from
[rfc5245bis] still need to be followed.
This document defines a supplementary mode of ICE operation, "Trickle
ICE", in which candidates can be exchanged incrementally as soon as
they become available (and simultaneously with the gathering of other
candidates). Connectivity checks can also start as soon as candidate
pairs have been created. Because Trickle ICE enables candidate
gathering and connectivity checks to be done in parallel, the method
can considerably accelerate the process of establishing a
communication session.
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This document also defines how to discover support for Trickle ICE,
how the procedures in [rfc5245bis] are modified or supplemented when
using Trickle ICE, and how a Trickle ICE agent can interoperate with
an ICE agent compliant to [rfc5245bis].
This document does not define any protocol-specific usage of Trickle
ICE. Instead, protocol-specific details for Trickle ICE are defined
in separate usage documents. Examples of such documents are
[I-D.ietf-mmusic-trickle-ice-sip] (which defines usage with the
Session Initiation Protocol (SIP) [RFC3261] and the Session
Description Protocol [RFC3261]) and [XEP-0176] (which defines usage
with XMPP [RFC6120]). However, some of the examples in the document
use SDP and the offer/answer model [RFC3264] to explain the
underlying concepts.
The following diagram illustrates a successful Trickle ICE exchange
with a using protocol that follows the offer/answer model:
Alice Bob
| Offer |
|---------------------------------------------->|
| Additional Candidates |
|---------------------------------------------->|
| Answer |
|<----------------------------------------------|
| Additional Candidates |
|<----------------------------------------------|
| Additional Candidates and Connectivity Checks |
|<--------------------------------------------->|
|<========== CONNECTION ESTABLISHED ===========>|
Figure 1: Flow
There is quite a bit of operational experience with the technique
behind Trickle ICE, going back as far as 2005 (when the XMPP Jingle
extension defined a "dribble mode" as specified in [XEP-0176]); this
document incorporates feedback from those who have implemented and
deployed the technique over the years.
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].
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This specification makes use of all terminology defined for
Interactive Connectivity Establishment in [rfc5245bis]. In addition,
it defines the following terms:
Full Trickle: The typical mode of operation for Trickle ICE agents,
in which the initial ICE description can include any number of
candidates (even zero candidates) and does not need to include a
full generation of candidates as in half trickle.
Generation: All of the candidates conveyed within an ICE session.
Half Trickle: A Trickle ICE mode of operation in which the initiator
gathers a full generation of candidates strictly before creating
and conveying the initial ICE description. Once conveyed, this
candidate information can be processed by regular ICE agents,
which do not require support for Trickle ICE. It also allows
Trickle ICE capable responders to still gather candidates and
perform connectivity checks in a non-blocking way, thus providing
roughly "half" the advantages of Trickle ICE. The half trickle
mechanism is mostly meant for use when the responder's support for
Trickle ICE cannot be confirmed prior to conveying the initial ICE
description.
ICE Description: Any attributes related to the ICE session (not
candidates) required to configure an ICE agent. These include but
are not limited to the username fragment, password, and other
attributes.
Trickled Candidates: Candidates that a Trickle ICE agent conveys
after conveying the initial ICE description or responding to the
initial ICE description, but within the same ICE session.
Trickled candidates can be conveyed in parallel with candidate
gathering and connectivity checks.
Trickling: The act of incrementally conveying trickled candidates.
Empty Check List: A check list that initially does not contain any
candidate pairs because they will be incrementally added as they
are trickled. (This scenario does not arise with a regular ICE
agent, because all candidate pairs are known when the agent
creates the check list set).
3. Determining Support for Trickle ICE
To fully support Trickle ICE, using protocols SHOULD incorporate one
of the following mechanisms so that implementations can determine
whether Trickle ICE is supported:
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1. Provide a capabilities discovery method so that agents can verify
support of Trickle ICE prior to initiating a session (XMPP's
Service Discovery [XEP-0030] is one such mechanism).
2. Make support for Trickle ICE mandatory so that user agents can
assume support.
If a using protocol does not provide a method of determining ahead of
time whether Trickle ICE is supported, agents can make use of the
half trickle procedure described in Section 12.
Prior to conveying the initial ICE description, agents that implement
using protocols that support capabilities discovery can attempt to
verify whether or not the remote party supports Trickle ICE. If an
agent determines that the remote party does not support Trickle ICE,
it MUST fall back to using regular ICE or abandon the entire session.
Even if a using protocol does not include a capabilities discovery
method, a user agent can provide an indication within the ICE
description that it supports Trickle ICE by communicating an ICE
option of 'trickle'. This token MUST be provided either at the
session level or, if at the data stream level, for every data stream
(an agent MUST NOT specify Trickle ICE support for some data streams
but not others). Note: The encoding of the 'trickle' ICE option, and
the message(s) used to carry it to the peer, are protocol specific;
for instance, the encoding for the Session Description Protocol (SDP)
[RFC4566] is defined in [I-D.ietf-mmusic-trickle-ice-sip].
Dedicated discovery semantics and half trickle are needed only prior
to session initiation. After a session is established and Trickle
ICE support is confirmed for both parties, either agent can use full
trickle for subsequent exchanges.
4. Conveying the Initial ICE Description
An initiator can start gathering candidates as soon as it has an
indication that communication is imminent (e.g., a user interface cue
or an explicit request to initiate a session). Unlike in regular
ICE, in Trickle ICE implementations do not need to gather candidates
in a blocking manner. Therefore, unless half trickle is being used,
the user experience is improved if the initiator generates and
transmits their initial ICE description as early as possible (thus
enabling the remote party to start gathering and trickling
candidates).
An initiator MAY include any mix of candidates when conveying the
initial ICE description. This includes the possibility of conveying
all the candidates the initiator plans to use (as in half trickle),
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conveying only a publicly-reachable IP address (e.g., a candidate at
a data relay that is known to not be behind a firewall), or conveying
no candidates at all (in which case the initiator can obtain the
responder's initial candidate list sooner and the responder can begin
candidate gathering more quickly).
Methods for calculating priorities and foundations, as well as
determining redundancy of candidates, work just as in regular ICE
[rfc5245bis] (with the exception of pruning of duplicate peer
reflexive candidates as described under Section 7.1).
5. Responder Procedures
When a responder receives the initial ICE description, it will first
check if the ICE description or initiator indicates support for
Trickle ICE as explained in Section 3. If not, the responder MUST
process the initial ICE description according to regular ICE
procedures [rfc5245bis] (or, if no ICE support is detected at all,
according to relevant processing rules for the using protocol, such
as offer/answer processing rules [RFC3264]). However, if support for
Trickle ICE is confirmed, a responder will automatically assume
support for regular ICE as well.
If the initial ICE description indicates support for Trickle ICE, the
responder will determine its role and start gathering and
prioritizing candidates; while doing so, it will also respond by
conveying its own ICE description, so that both the initiator and the
responder can start forming check lists and begin connectivity
checks.
5.1. Conveying the Initial Response
A responder can respond to the initial ICE description at any point
while gathering candidates. The ICE description in the response MAY
contain any set of candidates, including all candidates or no
candidates. (The benefit of including no candidates is to convey the
ICE description as quickly as possible, so that both parties can
consider the overall session to be under active negotiation as soon
as possible.)
As noted in Section 3, in using protocols that use SDP the
responder's ICE description can indicate support for Trickle ICE by
including a token of "trickle" in the ice-options attribute.
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6. Initiator Procedures
When processing the initial ICE description from a responder, the
initiator follows regular ICE procedures to determine its role, after
which it forms check lists (as described in Section 7.1) and begins
connectivity checks.
7. Performing Connectivity Checks
For the most part, Trickle ICE agents perform connectivity checks
following regular ICE procedures. However, the fact that gathering
and communicating candidates is asynchronous in Trickle ICE results
in several differences.
7.1. Forming Check Lists and Beginning Connectivity Checks
According to regular ICE procedures [rfc5245bis], in order for
candidate pairing to be possible and for duplicate candidates to be
pruned, the candidates would need to be provided in the relevant ICE
descriptions. By contrast, under Trickle ICE check lists can be
empty until candidates are conveyed or received. Therefore Trickle
ICE agents handle check list formation and candidate pairing in a
slightly different way than regular ICE agents: the agents still form
the check lists, but they populate a given check list only after they
actually have candidate pairs for that check list. Every check list
is initially placed in the Running state, even if the check list is
empty. An agent then begins connectivity checks (which includes
changing the state of some candidate pairs from Frozen to Waiting) as
defined in Section 6.1.2.6 of [rfc5245bis].
With regard to pruning of duplicate candidate pairs, a Trickle ICE
agent SHOULD follow a policy of keeping the higher priority candidate
unless it is peer reflexive.
7.2. Scheduling Checks
As specified in [rfc5245bis], whenever timer Ta fires, only check
lists in the Running state will be picked when scheduling
connectivity checks for candidate pairs.
Therefore, a Trickle ICE agent MUST keep each check list in the
Running state as long as it expects candidate pairs to be
incrementally added to the check list. After that, the check list
state is set according to the procedures in [rfc5245bis].
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7.3. Empty Check Lists
The state of an empty check list is initially set to Running, in
accordance with Section 6.1.2.1 of [rfc5245bis].
Whenever timer Ta fires, and an empty check list is picked, no action
is performed for the list. Without waiting for timer Ta to expire
again, the agent selects the next check list in the Running state, in
accordance with Section 6.1.4.2 of [rfc5245bis].
In accordance with the rules defined in Section 8.1.1, when inserting
a new candidate pair into an empty check list, the agent sets the
pair to a state of Waiting or Frozen as appropriate.
7.4. Setting Check List State to Failed
Section 7.2.5.3.3 of [rfc5245bis] requires that agents update check
lists and timer states upon completing a connectivity check
transaction. During such an update, regular ICE agents would set the
state of a check list to Failed if both of the following two
conditions are satisfied:
o all of the pairs in the check list are either in the Failed state
or Succeeded state; and
o there is not a pair in the valid list for each component of the
data stream.
With Trickle ICE, the above situation would often occur when
candidate gathering and trickling are still in progress, even though
it is quite possible that future checks will succeed. For this
reason, Trickle ICE agents add the following conditions to the above
list:
o all candidate gathering has completed and the agent is not
expecting to discover any new local candidates; and
o the remote agent has conveyed an end-of-candidates indication for
that check list as described in Section 8.2.
8. Discovering and Conveying Additional Local Candidates
After candidate information has been conveyed, agents will most
likely continue discovering new local candidates as STUN, TURN, and
other non-host candidate gathering mechanisms begin to yield results.
Whenever an agent discovers such a new candidate it will compute its
priority, type, foundation, and component ID according to regular ICE
procedures.
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The new candidate is then checked for redundancy against the existing
list of local candidates. If its transport address and base match
those of an existing candidate, it will be considered redundant and
will be ignored. This would often happen for server reflexive
candidates that match the host addresses they were obtained from
(e.g., when the latter are public IPv4 addresses). Contrary to
regular ICE, Trickle ICE agents will consider the new candidate
redundant regardless of its priority.
Next the agent "trickles" the newly discovered candidate(s) to the
remote agent. The actual delivery of the new candidates is handled
by a using protocol such as SIP or XMPP. Trickle ICE imposes no
restrictions on the way this is done (e.g., some using protocols
might choose not to trickle updates for server reflexive candidates
and instead rely on the discovery of peer reflexive ones).
When candidates are trickled, the using protocol MUST deliver each
candidate (and any end-of-candidates indication as described in
Section 8.2) to the receiving Trickle ICE implementation exactly once
and in the same order it was conveyed. If the using protocol
provides any candidate retransmissions, they need to be hidden from
the ICE implementation.
Also, candidate trickling needs to be correlated to a specific ICE
session, so that if there is an ICE restart, any delayed updates for
a previous session can be recognized as such and ignored by the
receiving party. For example, using protocols that signal candidates
via SDP might include a Username Fragment value in the corresponding
a=candidate line, such as:
a=candidate:1 1 UDP 2130706431 2001:db8::1 5000 typ host ufrag 8hhY
Or as another example, WebRTC implementations might include a
Username Fragment in the JavaScript objects that represent
candidates.
Note: The using protocol needs to provide a mechanism for both
parties to indicate and agree on the ICE session in force (as
identified by the Username Fragment and Password combination) so that
they have a consistent view of which candidates are to be paired.
This is especially important in the case of ICE restarts (see
Section 11).
Once the candidate has been conveyed to the remote party, the agent
checks if any remote candidates are currently known for this same
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stream and component. If not, the new candidate will simply be added
to the list of local candidates.
Otherwise, if the agent has already learned of one or more remote
candidates for this stream and component, it will begin pairing the
new local candidates with them and adding the pairs to the existing
check lists according to their priority.
Note: A Trickle ICE agent MUST NOT pair a local candidate until it
has been trickled to the remote agent.
8.1. Pairing Newly Learned Candidates and Updating Check Lists
Forming candidate pairs works as described in the ICE specification
[rfc5245bis]. However, adding the new pair to a check list happens
according to the following rules:
1. If the new pair's local candidate is server reflexive, the agent
MUST replace the candidate with its base before completing the
redundancy check in step 2.
2. The agent eliminates redundant pairs by following the rules in
Section 5.1.3 of [rfc5245bis], but only if the old pair has a
state of Waiting or Frozen (thus avoiding removal of pairs for
which connectivity checks are in flight or for which connectivity
checks have already yielded a definitive result).
3. If after the foregoing redundancy test the check list where the
pair is to be added already contains the maximum number of
candidate pairs (100 by default as per [rfc5245bis]), the agent
SHOULD discard any pairs in the Failed state to make room for the
new pair. If there are no such pairs, the agent SHOULD discard
the new pair.
4. Otherwise, add the new pair to the check list.
8.1.1. Inserting a New Pair in a Check List
Consider the following tabular representation of all check lists in
an agent (note that initially for one of the foundations, i.e., f5,
there are no candidate pairs):
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+-----------------+------+------+------+------+------+
| | f1 | f2 | f3 | f4 | f5 |
+-----------------+------+------+------+------+------+
| s1 (Audio.RTP) | F | F | F | | |
+-----------------+------+------+------+------+------+
| s2 (Audio.RTCP) | F | F | F | F | |
+-----------------+------+------+------+------+------+
| s3 (Video.RTP) | F | | | | |
+-----------------+------+------+------+------+------+
| s4 (Video.RTCP) | F | | | | |
+-----------------+------+------+------+------+------+
Figure 2: Example of Check List State
Each row in the table represents a component for a given data stream
(e.g., s1 and s2 might be the RTP and RTCP components for audio) and
thus a single check list in the check list set. Each column
represents one foundation. Each cell represents one candidate pair.
In the tables shown in this section, "F" stands for "frozen", "W"
stands for "waiting", and "S" stands for "succeeded"; in addition,
"^^" is used to notate newly-added candidate pairs.
When an agent commences ICE processing, in accordance with
Section 6.1.2.6 of [rfc5245bis], for each foundation it will unfreeze
the pair with the lowest component ID and, if the component IDs are
equal, with the highest priority (this is the topmost candidate pair
in every column). This initial state is shown in the following
table.
+-----------------+------+------+------+------+------+
| | f1 | f2 | f3 | f4 | f5 |
+-----------------+------+------+------+------+------+
| s1 (Audio.RTP) | W | W | W | | |
+-----------------+------+------+------+------+------+
| s2 (Audio.RTCP) | F | F | F | W | |
+-----------------+------+------+------+------+------+
| s3 (Video.RTP) | F | | | | |
+-----------------+------+------+------+------+------+
| s4 (Video.RTCP) | F | | | | |
+-----------------+------+------+------+------+------+
Figure 3: Initial Check List State
Then, as the checks proceed (see Section 7.2.5.4 of [rfc5245bis]),
for each pair that enters the Succeeded state (denoted here by "S"),
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the agent will unfreeze all pairs for all data streams with the same
foundation (e.g., if the pair in column 1, row 1 succeeds then the
agent will unfreeze the pair in column 1, rows 2, 3, and 4).
+-----------------+------+------+------+------+------+
| | f1 | f2 | f3 | f4 | f5 |
+-----------------+------+------+------+------+------+
| s1 (Audio.RTP) | S | W | W | | |
+-----------------+------+------+------+------+------+
| s2 (Audio.RTCP) | W | F | F | W | |
+-----------------+------+------+------+------+------+
| s3 (Video.RTP) | W | | | | |
+-----------------+------+------+------+------+------+
| s4 (Video.RTCP) | W | | | | |
+-----------------+------+------+------+------+------+
Figure 4: Check List State with Succeeded Candidate Pair
Trickle ICE preserves all of these rules as they apply to "static"
check list sets. This implies that if a Trickle ICE agent were to
begin connectivity checks with all of its pairs already present, the
way that pair states change is indistinguishable from that of a
regular ICE agent.
Of course, the major difference with Trickle ICE is that check list
sets can be dynamically updated because candidates can arrive after
connectivity checks have started. When this happens, an agent sets
the state of the newly formed pair as described below.
Rule 1: If the newly formed pair has the lowest component ID and, if
the component IDs are equal, the highest priority of any candidate
pair for this foundation (i.e., if it is the topmost pair in the
column), set the state to Waiting. For example, this would be the
case if the newly formed pair were placed in column 5, row 1. This
rule is consistent with Section 6.1.2.6 of [rfc5245bis].
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+-----------------+------+------+------+------+------+
| | f1 | f2 | f3 | f4 | f5 |
+-----------------+------+------+------+------+------+
| s1 (Audio.RTP) | S | W | W | | ^W^ |
+-----------------+------+------+------+------+------+
| s2 (Audio.RTCP) | W | F | F | W | |
+-----------------+------+------+------+------+------+
| s3 (Video.RTP) | W | | | | |
+-----------------+------+------+------+------+------+
| s4 (Video.RTCP) | W | | | | |
+-----------------+------+------+------+------+------+
Figure 5: Check List State with Newly Formed Pair, Rule 1
Rule 2: If there is at least one pair in the Succeeded state for this
foundation, set the state to Waiting. For example, this would be the
case if the pair in column 5, row 1 succeeded and the newly formed
pair were placed in column 5, row 2. This rule is consistent with
Section 7.2.5.3.3 of [rfc5245bis].
+-----------------+------+------+------+------+------+
| | f1 | f2 | f3 | f4 | f5 |
+-----------------+------+------+------+------+------+
| s1 (Audio.RTP) | S | W | W | | S |
+-----------------+------+------+------+------+------+
| s2 (Audio.RTCP) | W | F | F | W | ^W^ |
+-----------------+------+------+------+------+------+
| s3 (Video.RTP) | W | | | | |
+-----------------+------+------+------+------+------+
| s4 (Video.RTCP) | W | | | | |
+-----------------+------+------+------+------+------+
Figure 6: Check List State with Newly Formed Pair, Rule 2
Rule 3: In all other cases, set the state to Frozen. For example,
this would be the case if the newly formed pair were placed in column
3, row 3.
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+-----------------+------+------+------+------+------+
| | f1 | f2 | f3 | f4 | f5 |
+-----------------+------+------+------+------+------+
| s1 (Audio.RTP) | S | W | W | | S |
+-----------------+------+------+------+------+------+
| s2 (Audio.RTCP) | W | F | F | W | W |
+-----------------+------+------+------+------+------+
| s3 (Video.RTP) | W | | ^F^ | | |
+-----------------+------+------+------+------+------+
| s4 (Video.RTCP) | W | | | | |
+-----------------+------+------+------+------+------+
Figure 7: Check List State with Newly Formed Pair, Rule 3
8.2. Announcing End of Candidates
Once all candidate gathering is completed or expires for an ICE
session associated with a specific data stream, the agent will
generate an "end-of-candidates" indication for that session and
convey it to the remote agent via the signaling channel. Although
the exact form of the indication depends on the using protocol, the
indication MUST specify the generation (Username Fragment and
Password combination) so that an agent can correlate the end-of-
candidates indication with a particular ICE session. The indication
can be conveyed in the following ways:
o As part of an initiation request (which would typically be the
case with the initial ICE description for half trickle)
o Along with the last candidate an agent can send for a stream
o As a standalone notification (e.g., after STUN Binding requests or
TURN Allocate requests to a server time out and the agent is no
longer actively gathering candidates)
Conveying an end-of-candidates indication in a timely manner is
important in order to avoid ambiguities and speed up the conclusion
of ICE processing. In particular:
o A controlled Trickle ICE agent SHOULD convey an end-of-candidates
indication after it has completed gathering for a data stream,
unless ICE processing terminates before the agent has had a chance
to complete gathering.
o A controlling agent MAY conclude ICE processing prior to conveying
end-of-candidates indications for all streams. However, it is
RECOMMENDED for a controlling agent to convey end-of-candidates
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indications whenever possible for the sake of consistency and to
keep middleboxes and controlled agents up-to-date on the state of
ICE processing.
When conveying an end-of-candidates indication during trickling
(rather than as a part of the initial ICE description or a response
thereto), it is the responsibility of the using protocol to define
methods for associating the indication with one or more specific data
streams.
Receiving an end-of-candidates indication enables an agent to update
check list states and, in case valid pairs do not exist for every
component in every data stream, determine that ICE processing has
failed. It also enables an agent to speed up the conclusion of ICE
processing when a candidate pair has been validated but it involves
the use of lower-preference transports such as TURN. In such
situations, an implementation MAY choose to wait and see if higher-
priority candidates are received; in this case the end-of-candidates
indication provides a notification that such candidates are not
forthcoming.
An agent MAY also choose to generate an end-of-candidates indication
before candidate gathering has actually completed, if the agent
determines that gathering has continued for more than an acceptable
period of time. However, an agent MUST NOT convey any more
candidates after it has conveyed an end-of-candidates indication.
When performing half trickle, an agent SHOULD convey an end-of-
candidates indication together with its initial ICE description
unless it is planning to potentially trickle additional candidates
(e.g., in case the remote party turns out to support Trickle ICE).
After an agent conveys the end-of-candidates indication, it will
update the state of the corresponding check list as explained in
Section 7. Past that point, an agent MUST NOT trickle any new
candidates within this ICE session. Therefore, adding new candidates
to the negotiation is possible only through an ICE restart (see
Section 11).
This specification does not override regular ICE semantics for
concluding ICE processing. Therefore, even if end-of-candidates
indications are conveyed, an agent will still need to go through pair
nomination. Also, if pairs have been nominated for components and
data streams, ICE processing MAY still conclude even if end-of-
candidates indications have not been received for all streams. In
all cases, an agent MUST NOT trickle any new candidates within an ICE
session after nomination of a candidate pair as described in
Section 8.1.1 of [rfc5245bis].
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9. Receiving Additional Remote Candidates
At any time during ICE processing, a Trickle ICE agent might receive
new candidates from the remote agent. When this happens and no local
candidates are currently known for this same stream, the new remote
candidates are added to the list of remote candidates.
Otherwise, the new candidates are used for forming candidate pairs
with the pool of local candidates and they are added to the local
check lists as described in Section 8.1.
Once the remote agent has completed candidate gathering, it will
convey an end-of-candidates indication. Upon receiving such an
indication, the local agent MUST update check list states as per
Section 7. This might lead to some check lists being marked as
Failed.
10. Receiving an End-Of-Candidates Indication
When an agent receives an end-of-candidates indication for a specific
data stream, it will update the state of the relevant check list as
per Section 7. If the check list is still in the Running state after
the update, the agent will persist the fact that an end-of-candidates
indication has been received and take it into account in future
updates to the check list. After an agent has received an end-of-
candidates indication, it MUST ignore any newly received candidates
for that data stream or data session.
11. Subsequent Exchanges and ICE Restarts
Before conveying an end-of-candidates indication, either agent MAY
convey subsequent candidate information at any time allowed by the
using protocol. When this happens, agents will use [rfc5245bis]
semantics (e.g., checking of the Username Fragment and Password
combination to determine whether or not the new candidate information
requires an ICE restart. If an ICE restart occurs, the agents can
assume that Trickle ICE is still supported if support was determined
previously, and thus can engage in Trickle ICE behavior as they would
in an initial exchange of ICE descriptions where support was
determined through a capabilities discovery method.
12. Half Trickle
In half trickle, the initiator conveys the initial ICE description
with a usable but not necessarily full generation of candidates.
This ensures that the ICE description can be processed by a regular
ICE responder and is mostly meant for use in cases where support for
Trickle ICE cannot be confirmed prior to conveying the initial ICE
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description. The initial ICE description indicates support for
Trickle ICE, so that the responder can respond with something less
than a full generation of candidates and then trickle the rest. The
initial ICE description for half trickle can contain an end-of-
candidates indication, although this is not mandatory because if
trickle support is confirmed then the initiator can choose to trickle
additional candidates before it conveys an end-of-candidates
indication.
The half trickle mechanism can be used in cases where there is no way
for an agent to verify in advance whether a remote party supports
Trickle ICE. Because the initial ICE description contain a full
generation of candidates, it can thus be handled by a regular ICE
agent, while still allowing a Trickle ICE agent to use the
optimization defined in this specification. This prevents
negotiation from failing in the former case while still giving
roughly half the Trickle ICE benefits in the latter.
Use of half trickle is only necessary during an initial exchange of
ICE descriptions. After both parties have received an ICE
description from their peer, they can each reliably determine Trickle
ICE support and use it for all subsequent exchanges.
In some instances, using half trickle might bring more than just half
the improvement in terms of user experience. This can happen when an
agent starts gathering candidates upon user interface cues that the
user will soon be initiating an interaction, such as activity on a
keypad or the phone going off hook. This would mean that some or all
of the candidate gathering could be completed before the agent
actually needs to convey the candidate information. Because the
responder will be able to trickle candidates, both agents will be
able to start connectivity checks and complete ICE processing earlier
than with regular ICE and potentially even as early as with full
trickle.
However, such anticipation is not always possible. For example, a
multipurpose user agent or a WebRTC web page where communication is a
non-central feature (e.g., calling a support line in case of a
problem with the main features) would not necessarily have a way of
distinguishing between call intentions and other user activity. In
such cases, using full trickle is most likely to result in an ideal
user experience. Even so, using half trickle would be an improvement
over regular ICE because it would result in a better experience for
responders.
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13. Trickle ICE and Peer Reflexive Candidates
Even though Trickle ICE does not explicitly modify the procedures for
handling peer-reflexive candidates, use of Trickle ICE can have an
impact on how they are processed. With Trickle ICE, it is possible
that server reflexive candidates can be discovered as peer reflexive
in cases where incoming connectivity checks are received from these
candidates before the trickle updates that carry them.
While this would certainly increase the number of cases where ICE
processing nominates and selects candidates discovered as peer-
reflexive, it does not require any change in processing.
It is also likely that some using protocols would prefer not to
trickle server reflexive candidates to entities that are known to be
publicly accessible and where sending a direct STUN binding request
is likely to reach the destination faster than the trickle update
that travels through the signaling path.
14. Requirements for Using Protocols
In order to fully enable the use of Trickle ICE, this specification
defines the following requirements for using protocols.
o A using protocol SHOULD provide a way for parties to advertise and
discover support for Trickle ICE before an ICE session begins (see
Section 3).
o A using protocol MUST provide methods for incrementally conveying
(i.e., "trickling") additional candidates after conveying the
initial ICE description (see Section 8).
o A using protocol MUST deliver each trickled candidate or end-of-
candidates indication exactly once and in the same order it was
conveyed (see Section 8).
o A using protocol MUST provide a mechanism for both parties to
indicate and agree on the ICE session in force (see Section 8).
o A using protocol MUST provide a way for parties to communicate the
end-of-candidates indication, which MUST specify the particular
ICE session to which the indication applies (see Section 8.2).
15. Preserving Candidate Order while Trickling
One important aspect of regular ICE is that connectivity checks for a
specific foundation and component are attempted simultaneously by
both agents, so that any firewalls or NATs fronting the agents would
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whitelist both endpoints and allow all except for the first
("suicide") packets to go through. This is also important to
unfreezing candidates at the right time. While not crucial,
preserving this behavior in Trickle ICE is likely to improve ICE
performance.
To achieve this, when trickling candidates, agents SHOULD respect the
order of components as reflected by their component IDs; that is,
candidates for a given component SHOULD NOT be conveyed prior to
candidates for a component with a lower ID number within the same
foundation. In addition, candidates SHOULD be paired, following the
procedures in Section 8.1.1, in the same order they are conveyed.
For example, the following SDP description contains two components
(RTP and RTCP) and two foundations (host and server reflexive):
v=0
o=jdoe 2890844526 2890842807 IN IP4 10.0.1.1
s=
c=IN IP4 10.0.1.1
t=0 0
a=ice-pwd:asd88fgpdd777uzjYhagZg
a=ice-ufrag:8hhY
m=audio 5000 RTP/AVP 0
a=rtpmap:0 PCMU/8000
a=candidate:1 1 UDP 2130706431 10.0.1.1 5000 typ host
a=candidate:1 2 UDP 2130706431 10.0.1.1 5001 typ host
a=candidate:2 1 UDP 1694498815 192.0.2.3 5000 typ srflx
raddr 10.0.1.1 rport 8998
a=candidate:2 2 UDP 1694498815 192.0.2.3 5001 typ srflx
raddr 10.0.1.1 rport 8998
For this candidate information the RTCP host candidate would not be
conveyed prior to the RTP host candidate. Similarly the RTP server
reflexive candidate would be conveyed together with or prior to the
RTCP server reflexive candidate.
16. IANA Considerations
IANA is requested to register the following ICE option in the "ICE
Options" sub-registry of the "Interactive Connectivity Establishment
(ICE) registry", following the procedures defined in [RFC6336].
ICE Option: trickle
Contact: IESG, iesg@ietf.org
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Change control: IESG
Description: An ICE option of "trickle" indicates support for
incremental communication of ICE candidates.
Reference: RFC XXXX
17. Security Considerations
This specification inherits most of its semantics from [rfc5245bis]
and as a result all security considerations described there apply to
Trickle ICE.
If the privacy implications of revealing host addresses on an
endpoint device are a concern (see for example the discussion in
[I-D.ietf-rtcweb-ip-handling] and in Section 19 of [rfc5245bis]),
agents can generate ICE descriptions that contain no candidates and
then only trickle candidates that do not reveal host addresses (e.g.,
relayed candidates).
18. Acknowledgements
The authors would like to thank Bernard Aboba, Flemming Andreasen,
Rajmohan Banavi, Taylor Brandstetter, Philipp Hancke, Christer
Holmberg, Ari Keranen, Paul Kyzivat, Jonathan Lennox, Enrico Marocco,
Pal Martinsen, Nils Ohlmeier, Thomas Stach, Peter Thatcher, Martin
Thomson, Dale R. Worley, and Brandon Williams for their reviews and
suggestions on improving this document. Thanks also to Ari Keranen
and Peter Thatcher in their role as chairs, and Ben Campbell in his
role as responsible Area Director.
19. References
19.1. 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,
<https://www.rfc-editor.org/info/rfc2119>.
[rfc5245bis]
Keranen, A., Holmberg, C., and J. Rosenberg, "Interactive
Connectivity Establishment (ICE): A Protocol for Network
Address Translator (NAT) Traversal", draft-ietf-ice-
rfc5245bis-20 (work in progress), March 2018.
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19.2. Informative References
[I-D.ietf-mmusic-trickle-ice-sip]
Ivov, E., Stach, T., Marocco, E., and C. Holmberg, "A
Session Initiation Protocol (SIP) usage for Trickle ICE",
draft-ietf-mmusic-trickle-ice-sip-14 (work in progress),
February 2018.
[I-D.ietf-rtcweb-ip-handling]
Uberti, J. and G. Shieh, "WebRTC IP Address Handling
Requirements", draft-ietf-rtcweb-ip-handling-06 (work in
progress), March 2018.
[RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
and E. Lear, "Address Allocation for Private Internets",
BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996,
<https://www.rfc-editor.org/info/rfc1918>.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
DOI 10.17487/RFC3261, June 2002,
<https://www.rfc-editor.org/info/rfc3261>.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264,
DOI 10.17487/RFC3264, June 2002,
<https://www.rfc-editor.org/info/rfc3264>.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
July 2006, <https://www.rfc-editor.org/info/rfc4566>.
[RFC4787] Audet, F., Ed. and C. Jennings, "Network Address
Translation (NAT) Behavioral Requirements for Unicast
UDP", BCP 127, RFC 4787, DOI 10.17487/RFC4787, January
2007, <https://www.rfc-editor.org/info/rfc4787>.
[RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
"Session Traversal Utilities for NAT (STUN)", RFC 5389,
DOI 10.17487/RFC5389, October 2008,
<https://www.rfc-editor.org/info/rfc5389>.
[RFC5766] Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using
Relays around NAT (TURN): Relay Extensions to Session
Traversal Utilities for NAT (STUN)", RFC 5766,
DOI 10.17487/RFC5766, April 2010,
<https://www.rfc-editor.org/info/rfc5766>.
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[RFC6120] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 6120, DOI 10.17487/RFC6120,
March 2011, <https://www.rfc-editor.org/info/rfc6120>.
[RFC6336] Westerlund, M. and C. Perkins, "IANA Registry for
Interactive Connectivity Establishment (ICE) Options",
RFC 6336, DOI 10.17487/RFC6336, July 2011,
<https://www.rfc-editor.org/info/rfc6336>.
[XEP-0030]
Hildebrand, J., Millard, P., Eatmon, R., and P. Saint-
Andre, "XEP-0030: Service Discovery", XEP XEP-0030, June
2008.
[XEP-0176]
Beda, J., Ludwig, S., Saint-Andre, P., Hildebrand, J.,
Egan, S., and R. McQueen, "XEP-0176: Jingle ICE-UDP
Transport Method", XEP XEP-0176, June 2009.
Appendix A. Interaction with Regular ICE
The ICE protocol was designed to be flexible enough to work in and
adapt to as many network environments as possible. Despite that
flexibility, ICE as specified in [rfc5245bis] does not by itself
support trickle ICE. This section describes how trickling of
candidates interacts with ICE.
[rfc5245bis] describes the conditions required to update check lists
and timer states while an ICE agent is in the Running state. These
conditions are verified upon transaction completion and one of them
stipulates that:
If there is not a pair in the valid list for each component of the
data stream, the state of the check list is set to Failed.
This could be a problem and cause ICE processing to fail prematurely
in a number of scenarios. Consider the following case:
1. Alice and Bob are both located in different networks with Network
Address Translation (NAT). Alice and Bob themselves have
different address but both networks use the same private internet
block (e.g., the "20-bit block" 172.16/12 specified in
[RFC1918]).
2. Alice conveys to Bob the candidate 172.16.0.1 which also happens
to correspond to an existing host on Bob's network.
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3. Bob creates a check list consisting solely of 172.16.0.1 and
starts checks.
4. These checks reach the host at 172.16.0.1 in Bob's network, which
responds with an ICMP "port unreachable" error; per [rfc5245bis]
Bob marks the transaction as Failed.
At this point the check list only contains Failed candidates and the
valid list is empty. This causes the data stream and potentially all
ICE processing to fail, even though if Trickle ICE agents could
subsequently convey candidates that would cause previously empty
check lists to become non-empty.
A similar race condition would occur if the initial ICE description
from Alice contain only candidates that can be determined as
unreachable from any of the candidates that Bob has gathered (e.g.,
this would be the case if Bob's candidates only contain IPv4
addresses and the first candidate that he receives from Alice is an
IPv6 one).
Another potential problem could arise when a non-trickle ICE
implementation initiates an interaction with a Trickle ICE
implementation. Consider the following case:
1. Alice's client has a non-Trickle ICE implementation.
2. Bob's client has support for Trickle ICE.
3. Alice and Bob are behind NATs with address-dependent filtering
[RFC4787].
4. Bob has two STUN servers but one of them is currently
unreachable.
After Bob's agent receives Alice's initial ICE description it would
immediately start connectivity checks. It would also start gathering
candidates, which would take a long time because of the unreachable
STUN server. By the time Bob's answer is ready and conveyed to
Alice, Bob's connectivity checks might have failed: until Alice gets
Bob's answer, she won't be able to start connectivity checks and
punch holes in her NAT. The NAT would hence be filtering Bob's
checks as originating from an unknown endpoint.
Appendix B. Interaction with ICE Lite
The behavior of ICE lite agents that are capable of Trickle ICE does
not require any particular rules other than those already defined in
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this specification and [rfc5245bis]. This section is hence provided
only for informational purposes.
An ICE lite agent would generate candidate information as per
[rfc5245bis] and would indicate support for Trickle ICE. Given that
the candidate information will contain a full generation of
candidates, it would also be accompanied by an end-of-candidates
indication.
When performing full trickle, a full ICE implementation could convey
the initial ICE description or response thereto with no candidates.
After receiving a response that identifies the remote agent as an ICE
lite implementation, the initiator can choose to not trickle any
additional candidates. The same is also true in the case when the
ICE lite agent initiates the interaction and the full ICE agent is
the responder. In these cases the connectivity checks would be
enough for the ICE lite implementation to discover all potentially
useful candidates as peer reflexive. The following example
illustrates one such ICE session using SDP syntax:
ICE Lite Bob
Agent
| Offer (a=ice-lite a=ice-options:trickle) |
|---------------------------------------------->|
| |no cand
| Answer (a=ice-options:trickle) |trickling
|<----------------------------------------------|
| Connectivity Checks |
|<--------------------------------------------->|
peer rflx| |
cand disco| |
|<========== CONNECTION ESTABLISHED ===========>|
Figure 8: Example
In addition to reducing signaling traffic this approach also removes
the need to discover STUN bindings or make TURN allocations, which
can considerably lighten ICE processing.
Appendix C. Changes from Earlier Versions
Note to the RFC Editor: please remove this section prior to
publication as an RFC.
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C.1. Changes from draft-ietf-ice-trickle-18
o Cleaned up pairing and redundancy checking rules for newly
discovered candidates per IESG feedback and WG discussion.
o Improved wording in half trickle section.
o Changed "not more than once" to "exactly once".
o Changed NAT examples back to IPv4.
C.2. Changes from draft-ietf-ice-trickle-17
o Simplified the rules for inserting a new pair in a check list.
o Clarified it is not allowed to nominate a candidate pair after a
pair has already been nominated (a.k.a. renomination or
continuous nomination).
o Removed some text that referenced older versions of rfc5245bis.
o Removed some text that duplicated concepts and procedures
specified in rfc5245bis.
o Removed the ill-defined concept of stream order.
o Shortened the introduction.
C.3. Changes from draft-ietf-ice-trickle-16
o Made "ufrag" terminology consistent with 5245bis.
o Applied in-order delivery rule to end-of-candidates indication.
C.4. Changes from draft-ietf-ice-trickle-15
o Adjustments to address AD review feedback.
C.5. Changes from draft-ietf-ice-trickle-14
o Minor modifications to track changes to ICE core.
C.6. Changes from draft-ietf-ice-trickle-13
o Removed independent monitoring of check list "states" of frozen or
active, since this is handled by placing a check list in the
Running state defined in ICE core.
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C.7. Changes from draft-ietf-ice-trickle-12
o Specified that the end-of-candidates indication must include the
generation (ufrag/pwd) to enable association with a particular ICE
session.
o Further editorial fixes to address WGLC feedback.
C.8. Changes from draft-ietf-ice-trickle-11
o Editorial and terminological fixes to address WGLC feedback.
C.9. Changes from draft-ietf-ice-trickle-10
o Minor editorial fixes.
C.10. Changes from draft-ietf-ice-trickle-09
o Removed immediate unfreeze upon Fail.
o Specified MUST NOT regarding ice-options.
o Changed terminology regarding initial ICE parameters to avoid
implementer confusion.
C.11. Changes from draft-ietf-ice-trickle-08
o Reinstated text about in-order processing of messages as a
requirement for signaling protocols.
o Added IANA registration template for ICE option.
o Corrected Case 3 rule in Section 8.1.1 to ensure consistency with
regular ICE rules.
o Added tabular representations to Section 8.1.1 in order to
illustrate the new pair rules.
C.12. Changes from draft-ietf-ice-trickle-07
o Changed "ICE description" to "candidate information" for
consistency with 5245bis.
C.13. Changes from draft-ietf-ice-trickle-06
o Addressed editorial feedback from chairs' review.
o Clarified terminology regarding generations.
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C.14. Changes from draft-ietf-ice-trickle-05
o Rewrote the text on inserting a new pair into a check list.
C.15. Changes from draft-ietf-ice-trickle-04
o Removed dependency on SDP and offer/answer model.
o Removed mentions of aggressive nomination, since it is deprecated
in 5245bis.
o Added section on requirements for signaling protocols.
o Clarified terminology.
o Addressed various WG feedback.
C.16. Changes from draft-ietf-ice-trickle-03
o Provided more detailed description of unfreezing behavior,
specifically how to replace pre-existing peer-reflexive candidates
with higher-priority ones received via trickling.
C.17. Changes from draft-ietf-ice-trickle-02
o Adjusted unfreezing behavior when there are disparate foundations.
C.18. Changes from draft-ietf-ice-trickle-01
o Changed examples to use IPv6.
C.19. Changes from draft-ietf-ice-trickle-00
o Removed dependency on SDP (which is to be provided in a separate
specification).
o Clarified text about the fact that a check list can be empty if no
candidates have been sent or received yet.
o Clarified wording about check list states so as not to define new
states for "Active" and "Frozen" because those states are not
defined for check lists (only for candidate pairs) in ICE core.
o Removed open issues list because it was out of date.
o Completed a thorough copy edit.
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C.20. Changes from draft-mmusic-trickle-ice-02
o Addressed feedback from Rajmohan Banavi and Brandon Williams.
o Clarified text about determining support and about how to proceed
if it can be determined that the answering agent does not support
Trickle ICE.
o Clarified text about check list and timer updates.
o Clarified when it is appropriate to use half trickle or to send no
candidates in an offer or answer.
o Updated the list of open issues.
C.21. Changes from draft-ivov-01 and draft-mmusic-00
o Added a requirement to trickle candidates by order of components
to avoid deadlocks in the unfreezing algorithm.
o Added an informative note on peer-reflexive candidates explaining
that nothing changes for them semantically but they do become a
more likely occurrence for Trickle ICE.
o Limit the number of pairs to 100 to comply with 5245.
o Added clarifications on the non-importance of how newly discovered
candidates are trickled/sent to the remote party or if this is
done at all.
o Added transport expectations for trickled candidates as per Dale
Worley's recommendation.
C.22. Changes from draft-ivov-00
o Specified that end-of-candidates is a media level attribute which
can of course appear as session level, which is equivalent to
having it appear in all m-lines. Also made end-of-candidates
optional for cases such as aggressive nomination for controlled
agents.
o Added an example for ICE lite and Trickle ICE to illustrate how,
when talking to an ICE lite agent doesn't need to send or even
discover any candidates.
o Added an example for ICE lite and Trickle ICE to illustrate how,
when talking to an ICE lite agent doesn't need to send or even
discover any candidates.
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o Added wording that explicitly states ICE lite agents have to be
prepared to receive no candidates over signaling and that they
should not freak out if this happens. (Closed the corresponding
open issue).
o It is now mandatory to use MID when trickling candidates and using
m-line indexes is no longer allowed.
o Replaced use of 0.0.0.0 to IP6 :: in order to avoid potential
issues with RFC2543 SDP libraries that interpret 0.0.0.0 as an on-
hold operation. Also changed the port number here from 1 to 9
since it already has a more appropriate meaning. (Port change
suggested by Jonathan Lennox).
o Closed the Open Issue about use about what to do with cands
received after end-of-cands. Solution: ignore, do an ICE restart
if you want to add something.
o Added more terminology, including trickling, trickled candidates,
half trickle, full trickle,
o Added a reference to the SIP usage for Trickle ICE as requested at
the Boston interim.
C.23. Changes from draft-rescorla-01
o Brought back explicit use of Offer/Answer. There are no more
attempts to try to do this in an O/A independent way. Also
removed the use of ICE Descriptions.
o Added SDP specification for trickled candidates, the trickle
option and 0.0.0.0 addresses in m-lines, and end-of-candidates.
o Support and Discovery. Changed that section to be less abstract.
As discussed in IETF85, the draft now says implementations and
usages need to either determine support in advance and directly
use trickle, or do half trickle. Removed suggestion about use of
discovery in SIP or about letting implementing protocols do what
they want.
o Defined Half Trickle. Added a section that says how it works.
Mentioned that it only needs to happen in the first o/a (not
necessary in updates), and added Jonathan's comment about how it
could, in some cases, offer more than half the improvement if you
can pre-gather part or all of your candidates before the user
actually presses the call button.
o Added a short section about subsequent offer/answer exchanges.
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o Added a short section about interactions with ICE Lite
implementations.
o Added two new entries to the open issues section.
C.24. Changes from draft-rescorla-00
o Relaxed requirements about verifying support following a
discussion on MMUSIC.
o Introduced ICE descriptions in order to remove ambiguous use of
3264 language and inappropriate references to offers and answers.
o Removed inappropriate assumption of adoption by RTCWEB pointed out
by Martin Thomson.
Authors' Addresses
Emil Ivov
Atlassian
303 Colorado Street, #1600
Austin, TX 78701
USA
Phone: +1-512-640-3000
Email: eivov@atlassian.com
Eric Rescorla
RTFM, Inc.
2064 Edgewood Drive
Palo Alto, CA 94303
USA
Phone: +1 650 678 2350
Email: ekr@rtfm.com
Justin Uberti
Google
747 6th St S
Kirkland, WA 98033
USA
Phone: +1 857 288 8888
Email: justin@uberti.name
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Peter Saint-Andre
Mozilla
P.O. Box 787
Parker, CO 80134
USA
Phone: +1 720 256 6756
Email: stpeter@mozilla.com
URI: https://www.mozilla.com/
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