<?xmlversion="1.0" encoding="UTF-8"?> <?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?>version='1.0' encoding='utf-8'?> <!DOCTYPE rfc SYSTEM"rfc2629.dtd">"rfc2629-xhtml.ent"> <rfccategory='std' ipr='trust200902' docName='draft-ietf-ice-trickle-21'> <?rfc toc='yes' ?> <?rfc symrefs='yes' ?> <?rfc sortrefs='yes'?> <?rfc iprnotified='no' ?> <?rfc strict='yes' ?> <?rfc compact='yes' ?>xmlns:xi="http://www.w3.org/2001/XInclude" category="std" ipr="trust200902" number="8838" submissionType="IETF" consensus="yes" obsoletes="" updates="" xml:lang="en" tocInclude="true" symRefs="true" sortRefs="true" version="3" docName="draft-ietf-ice-trickle-21"> <!-- xml2rfc v2v3 conversion 2.44.0 --> <front> <titleabbrev='Trickle ICE'>abbrev="Trickle ICE"> Trickle ICE: Incremental Provisioning of Candidates for the Interactive Connectivity Establishment (ICE) Protocol </title> <seriesInfo name="RFC" value="8838"/> <author fullname="Emil Ivov" initials="E." surname="Ivov"> <organization abbrev="8x8 / Jitsi">8x8, Inc. / Jitsi</organization> <address> <postal> <street>675 Creekside Way</street> <city>Campbell</city> <region>CA</region> <code>95008</code> <country>United States of America</country> </postal> <phone>+1 512 420 6968</phone> <email>emcho@jitsi.org</email> </address> </author> <!-- <authorinitials='E.' surname='Ivov' fullname='Emil Ivov'>initials="E." surname="Ivov" fullname="Emil Ivov"> <organizationabbrev='Atlassian'>Atlassian</organization>abbrev="Atlassian">Atlassian</organization> <address> <postal> <street>303 Colorado Street, #1600</street> <city>Austin</city> <region>TX</region> <code>78701</code><country>USA</country> </postal> <phone>+1-512-640-3000</phone> <email>eivov@atlassian.com</email> </address> </author> <author fullname="Eric Rescorla" initials="E.K." surname="Rescorla"> <organization>RTFM, Inc.</organization> <address> <postal> <street>2064 Edgewood Drive</street> <city>Palo Alto</city> <region>CA</region> <code>94303</code> <country>USA</country><country>United States of America</country> </postal> <phone>+1650 678 2350</phone> <email>ekr@rtfm.com</email>512 640 3000</phone> <email>emcho@jitsi.org</email> </address> </author> --> <!-- [rfced] As you may remember, this document was previously in AUTH48 state during 2018. The changes made during that time remain. This includes that Eric Rescorla was removed as an author per his request 2018-09-17. Here is a diff file that shows only the changes since this document was previously in AUTH48: https://www.rfc-editor.org/authors/rfc8838-previousround-diff.html (Some minor formatting changes are a result of the change to v3 XML.) If you would like us to forward all mails related to that previous round of AUTH48, please let us know. --> <author fullname="Justin Uberti" initials="J." surname="Uberti"> <organization>Google</organization> <address> <postal> <street>747 6thStStreet S</street> <city>Kirkland</city> <region>WA</region> <code>98033</code><country>USA</country><country>United States of America</country> </postal> <phone>+1 857 288 8888</phone> <email>justin@uberti.name</email> </address> </author> <author initials="P." surname="Saint-Andre" fullname="Peter Saint-Andre"> <organization>Mozilla</organization> <address> <postal> <street>P.O. Box 787</street> <city>Parker</city> <region>CO</region> <code>80134</code><country>USA</country><country>United States of America</country> </postal> <phone>+1 720 256 6756</phone> <email>stpeter@mozilla.com</email> <uri>https://www.mozilla.com/</uri> </address> </author> <date/>month="May" year="2020"/> <abstract> <t> 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 exchanging candidates over time instead of all at once. This method can considerably accelerate the process of establishing a communication session. </t> </abstract> </front> <middle> <sectiontitle='Introduction'>numbered="true" toc="default"> <name>Introduction</name> <t> The Interactive Connectivity Establishment (ICE) protocol <xreftarget="rfc5245bis"/>target="RFC8445" format="default"/> describes how an ICE agent gathers candidates, exchanges candidates with a peer ICE agent, and creates candidate pairs. Once the pairs have been gathered, the ICE agent will perform connectivitychecks,checks and eventually nominate and select pairs that will be used for sending and receiving data within a communication session. </t> <!--[rfced] RFC 5766 has been obsoleted by RFC 8656. May the reference (and the corresponding citation) be changed to RFC 8656? --> <t> Following the procedures in <xreftarget="rfc5245bis"/>target="RFC8445" format="default"/> can lead to somewhat lengthy establishment times for communication sessions, because candidate gathering often involves queryingSTUNSession Traversal Utilities for NAT (STUN) servers <xreftarget="RFC5389"/>target="RFC5389" format="default"/> and allocating relayed candidatesusing TURNon Traversal Using Relay NAT (TURN) servers <xreftarget="RFC5766"/>.target="RFC8656" format="default"/>. Although many ICE procedures can be completed in parallel, the pacing requirements from <xreftarget="rfc5245bis"/>target="RFC8445" format="default"/> still need to be followed. </t> <t> This document defines "Trickle ICE", a supplementary mode of ICE operation 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. </t> <t> This document also defines how to discover support for Trickle ICE, how the procedures in <xreftarget="rfc5245bis"/>target="RFC8445" format="default"/> are modified or supplemented when using Trickle ICE, and how a Trickle ICE agent can interoperate with an ICE agent compliant to <xreftarget="rfc5245bis"/>.target="RFC8445" format="default"/>. </t> <t> 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 <xreftarget="I-D.ietf-mmusic-trickle-ice-sip"/>target="RFC8840" format="default"/> (which defines usage with the Session Initiation Protocol (SIP) <xreftarget='RFC3261'/>target="RFC3261" format="default"/> and the Session Description Protocol (SDP) <xreftarget='RFC3261'/>)target="RFC4566" format="default"/>) and <xreftarget='XEP-0176'/>target="XEP-0176" format="default"/> (which defines usage withXMPPthe Extensible Messaging and Presence Protocol (XMPP) <xreftarget='RFC6120'/>).target="RFC6120" format="default"/>). However, some of the examples in the document use SDP and theoffer/answerOffer/Answer model <xreftarget='RFC3264'/>target="RFC3264" format="default"/> to explain the underlying concepts. </t> <t> The following diagram illustrates a successful Trickle ICE exchange with a using protocol that follows theoffer/answerOffer/Answer model: </t> <figuretitle="Flow"anchor="fig-flow"><artwork> <![CDATA[<name>Flow</name> <artwork name="" type="" align="left" alt=""><![CDATA[ Alice Bob | Offer | |---------------------------------------------->| | Additional Candidates | |---------------------------------------------->| | Answer | |<----------------------------------------------| | Additional Candidates | |<----------------------------------------------| | Additional Candidates and Connectivity Checks | |<--------------------------------------------->| |<========== CONNECTION ESTABLISHED ===========>|]]> </artwork>]]></artwork> </figure> <t> The main body of this document is structured to describe the behavior of Trickle ICE agents in roughly the order of operations and interactions during an ICE session:<list style='numbers'> <t>Determining</t> <ol spacing="normal" type="1"> <li>Determining support fortrickle ICE</t> <t>GeneratingTrickle ICE</li> <li>Generating the initial ICEdescription</t> <t>Handlingdescription</li> <li>Handling the initial ICE description and generating the initial ICEresponse</t> <t>Handlingresponse</li> <li>Handling the initial ICEresponse</t> <t>Forming check lists,response</li> <li>Forming checklists, pruning candidates, performing connectivity checks,etc.</t> <t>Gatheringetc.</li> <li>Gathering and conveying candidates after the initial ICE description andresponse</t> <t>Handlingresponse</li> <li>Handling inbound trickledcandidates</t> <t>Generatingcandidates</li> <li>Generating and handling the end-of-candidatesindication</t> <t>Handlingindication</li> <li>Handling ICErestarts</t> </list> </t>restarts</li> </ol> <t> 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 <xreftarget='XEP-0176'/>);target="XEP-0176" format="default"/>); this document incorporates feedback from those who have implemented and deployed the technique over the years. </t> </section> <sectiontitle="Terminology">numbered="true" toc="default"> <name>Terminology</name> <t> The key words"MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY","<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>", "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>", "<bcp14>MAY</bcp14>", and"OPTIONAL""<bcp14>OPTIONAL</bcp14>" in this document are to be interpreted as described in BCP 14 <xreftarget="RFC2119"/>.target="RFC2119"/> <xref target="RFC8174"/> when, and only when, they appear in all capitals, as shown here. </t> <t> This specification makes use of all terminology defined for Interactive Connectivity Establishment in <xreftarget="rfc5245bis"/>.target="RFC8445" format="default"/>. In addition, it defines the following terms: </t><t> <list style="hanging"> <t hangText="Full Trickle:"><dl newline="false" spacing="normal"> <dt>Empty Checklist:</dt> <dd> A checklist 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 checklist set.) </dd> <dt>Full Trickle:</dt> <dd> 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.</t> <t hangText="Generation:"></dd> <dt>Generation:</dt> <dd> All of the candidates conveyed within an ICEsession. </t> <t hangText="Half Trickle:">session (correlated with a particular Username Fragment and Password combination). </dd> <dt>Half Trickle:</dt> <dd> 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 allowsTrickle ICE capableTrickle-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. Thehalf tricklehalf-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.</t> <t hangText="ICE Description:"></dd> <dt>ICE Description:</dt> <dd> Any attributes related to the ICE session(not(other than candidates) required to configure an ICE agent. These include but are not limited to theusername fragment, password,Username Fragment, the Password, and other attributes.</t> <t hangText="Trickled Candidates:"></dd> <dt>Trickled Candidates:</dt> <dd> Candidates that a Trickle ICE agent conveys after conveyingthe initial ICE descriptionor 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.</t> <t hangText="Trickling:"></dd> <dt>Trickling:</dt> <dd> The act of incrementally conveying trickled candidates.</t> <t hangText="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). </t> </list> </t></dd> </dl> </section> <sectiontitle='Determininganchor="support" numbered="true" toc="default"> <name>Determining Support for TrickleICE' anchor="support">ICE</name> <t> To fully support Trickle ICE, using protocolsSHOULD<bcp14>SHOULD</bcp14> incorporate one of the following mechanisms so that implementations can determine whether Trickle ICE is supported: </t><t> <list style='numbers'> <t><ol spacing="normal" type="1"> <li> Provide a capabilities discovery method so that agents can verify support of Trickle ICE prior to initiating a session (XMPP's <xreftarget="XEP-0030">Servicetarget="XEP-0030" format="default">Service Discovery</xref> is one such mechanism).</t> <t></li> <li> Make support for Trickle ICE mandatory so that user agents can assume support.</t> </list> </t></li> </ol> <t> If a using protocol does not provide a method of determining ahead of time whether Trickle ICE is supported, agents can make use of thehalf tricklehalf-trickle procedure described in <xreftarget="half-trickle"/>.target="half-trickle" format="default"/>. </t> <t> 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, itMUST<bcp14>MUST</bcp14> fall back to using regular ICE or abandon the entire session. </t> <t> 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 tokenMUST<bcp14>MUST</bcp14> be provided either at the session level or, if at the data stream level, for every data stream (an agentMUST NOT<bcp14>MUST NOT</bcp14> 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 forthe Session Description Protocol (SDP)SDP <xreftarget='RFC4566'/>target="RFC4566" format="default"/> is defined in <xreftarget='I-D.ietf-mmusic-trickle-ice-sip'/>.target="RFC8840" format="default"/>. </t> <t> Dedicated discovery semantics and half trickle are needed only prior to initiation of an ICE session. After an ICE session is established and Trickle ICE support is confirmed for both parties, either agent can use full trickle for subsequent exchanges (see also <xreftarget='subsequent'/>).target="subsequent" format="default"/>). </t> </section> <sectiontitle='Generatinganchor="initial" numbered="true" toc="default"> <name>Generating the Initial ICEDescription' anchor="initial">Description</name> <t> An ICE agent can start gathering candidates as soon as it has an indication that communication is imminent (e.g., auser interfaceuser-interface cue or an explicit request to initiate a communication 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 initiating agent generates and transmits its initial ICE description as early as possible (thus enabling the remote party to start gathering and trickling candidates). </t> <t> An initiatorMAY<bcp14>MAY</bcp14> 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), conveying only apublicly-reachablepublicly 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 listsoonersooner, and the responder can begin candidate gathering more quickly). </t> <t> For candidates included in the initial ICE description, the methods for calculating priorities and foundations, determining redundancy of candidates, and the like work just as in regular ICE <xreftarget="rfc5245bis"/>.target="RFC8445" format="default"/>. </t> </section> <sectiontitle='Handlingnumbered="true" toc="default"> <name>Handling the Initial ICE Description and Generating the Initial ICEResponse' >Response</name> <t> 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 <xreftarget="support"/>.target="support" format="default"/>. If not, the responderMUST<bcp14>MUST</bcp14> process the initial ICE description according to regular ICE procedures <xreftarget="rfc5245bis"/>target="RFC8445" format="default"/> (or, if no ICE support is detected at all, according to relevant processing rules for the using protocol, such asoffer/answerOffer/Answer processing rules <xreftarget="RFC3264"/>).target="RFC3264" format="default"/>). However, if support for Trickle ICE is confirmed, a responder will automatically assume support for regular ICE as well. </t> <t> 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 an initial ICE response, so that both the initiator and the responder can formcheck listschecklists and begin connectivity checks. </t> <t> A responder can respond to the initial ICE description at any point while gathering candidates. The initial ICE responseMAY<bcp14>MAY</bcp14> contain any set of candidates, including all candidates or no candidates. (The benefit of including no candidates is to convey the initial ICE response as quickly as possible, so that both parties can consider the ICE session to be under active negotiation as soon as possible.) </t> <t> As noted in <xreftarget="support"/>,target="support" format="default"/>, in using protocols that useSDPSDP, the initial ICE response can indicate support for Trickle ICE by including a token of"trickle"'trickle' in the ice-options attribute. </t> </section> <sectiontitle="Handlingnumbered="true" toc="default"> <name>Handling the Initial ICEResponse">Response</name> <t> When processing the initial ICE response, the initiator follows regular ICE procedures to determine its role, after which it formscheck listschecklists (<xreftarget="checklists"/>)target="checklists" format="default"/>) and performs connectivity checks (<xreftarget='checks'/>).target="checks" format="default"/>). </t> </section> <sectiontitle='Forming Check Lists' anchor='checklists'>anchor="checklists" numbered="true" toc="default"> <name>Forming Checklists</name> <t> According to regular ICE procedures <xreftarget="rfc5245bis"/>,target="RFC8445" format="default"/>, in order for candidate pairing to be possible and for redundant candidates to be pruned, the candidates would need to be provided in the initial ICE description and initial ICE response. By contrast, under TrickleICE check listsICE, checklists can be empty until candidates are conveyed or received.ThereforeTherefore, a Trickle ICE agent handlescheck listchecklist formation and candidate pairing in a slightly different way than a regular ICE agent: the agent still forms thecheck lists,checklists, but it populates a givencheck listchecklist only after it actually has candidate pairs for thatcheck list.checklist. Everycheck listchecklist is initially placed in the Running state, even if thecheck listchecklist is empty (this is consistent withSection 6.1.2.1 of<xreftarget='rfc5245bis'/>).target="RFC8445" sectionFormat="of" section="6.1.2.1"/>). </t> </section> <sectiontitle='Performinganchor="checks" numbered="true" toc="default"> <name>Performing ConnectivityChecks' anchor='checks'>Checks</name> <t> As specified in <xreftarget='rfc5245bis'/>,target="RFC8445" format="default"/>, whenever timer Ta fires, onlycheck listschecklists in the Running state will be picked when scheduling connectivity checks for candidate pairs. Therefore, a Trickle ICE agentMUST<bcp14>MUST</bcp14> keep eachcheck listchecklist in the Running state as long as it expects candidate pairs to be incrementally added to thecheck list.checklist. After that, thecheck listchecklist state is set according to the procedures in <xreftarget='rfc5245bis'/>.target="RFC8445" format="default"/>. </t> <t> Whenever timer Ta fires and an emptycheck listchecklist is picked, no action is performed for the list. Without waiting for timer Ta to expire again, the agent selects the nextcheck listchecklist in the Running state, in accordance withSection 6.1.4.2 of<xreftarget='rfc5245bis'/>.target="RFC8445" format="default" sectionFormat="of" section="6.1.4.2"/>. </t> <t>Section 7.2.5.3.3 of<xreftarget='rfc5245bis'/>target="RFC8445" format="default" sectionFormat="of" section="7.2.5.4"/> requires that agents updatecheck listschecklists and timer states upon completing a connectivity check transaction. During such an update, regular ICE agents would set the state of acheck listchecklist to Failed if both of the following two conditions are satisfied: </t><t> <list style="symbols"> <t><ul spacing="normal"> <li> all of the pairs in thecheck listchecklist areeitherin either the Failed state or the Succeeded state; and</t> <t></li> <li> there is not a pair in the valid list for each component of the data stream.</t> </list> </t></li> </ul> <t> 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: </t><t> <list style="symbols"> <t><ul spacing="normal"> <li> all candidate gathering hascompletedcompleted, and the agent is not expecting to discover any new local candidates; and</t> <t></li> <li> the remote agent has conveyed an end-of-candidates indication for thatcheck listchecklist as described in <xreftarget="end-of-candidates.send"/>. </t> </list> </t>target="end-of-candidates.send" format="default"/>. </li> </ul> </section> <sectiontitle='Gatheringanchor="trickle-send" numbered="true" toc="default"> <name>Gathering and Conveying Newly Gathered LocalCandidates' anchor="trickle-send">Candidates</name> <t> After Trickle ICE agents have conveyed initial ICE descriptions and initial ICE responses, they will most likely continue gathering new local candidates as STUN, TURN, and other non-host candidate gathering mechanisms begin to yield results. Whenever an agent discovers such a newcandidatecandidate, it will compute its priority, type, foundation, and component ID according to regular ICE procedures. </t> <t> 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 forserver reflexiveserver-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. </t> <t>NextNext, 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 forserver reflexiveserver-reflexive candidates and instead rely on the discovery ofpeer reflexivepeer-reflexive ones). </t> <t> When candidates are trickled, the using protocolMUST<bcp14>MUST</bcp14> deliver each candidate (and any end-of-candidates indication as described in <xreftarget='end-of-candidates.send'/>)target="end-of-candidates.send" format="default"/>) 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. </t> <t> 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:<figure> <artwork> <![CDATA[</t> <sourcecode type="sdp"><![CDATA[ a=candidate:1 1 UDP 2130706431 2001:db8::1 5000 typ host ufrag 8hhY]]> </artwork> </figure>]]></sourcecode> <t> Or, as another example, WebRTC implementations might include a Username Fragment in the JavaScript objects that represent candidates. </t> <t> 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 Passwordcombination)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 <xreftarget='subsequent'/>).target="subsequent" format="default"/>). </t> <t> Note: A using protocol might prefer not to trickleserver reflexiveserver-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. </t> </section> <sectiontitle='Pairinganchor="local-pairing" numbered="true" toc="default"> <name>Pairing Newly Gathered LocalCandidates' anchor="local-pairing">Candidates</name> <t> As a Trickle ICE agent gathers local candidates, it needs to form candidate pairs; this works as described in the ICE specification <xreftarget='rfc5245bis'/>,target="RFC8445" format="default"/>, with the following provisos:<list style='numbers'> <t></t> <ol spacing="normal" type="1"> <li> A Trickle ICE agentMUST NOT<bcp14>MUST NOT</bcp14> pair a local candidate until it has been trickled to the remote party.</t> <t></li> <li> Once the agent has conveyed the local candidate to the remote party, the agent checks if any remote candidates are currently known for this same stream and component. If not, the agent merely adds the new candidate to the list of local candidates (without pairing it).</t> <t></li> <li> Otherwise, if the agent has already learned of one or more remote candidates for this stream and component, it attempts to pair the new local candidate as described in the ICE specification <xreftarget='rfc5245bis'/>. </t> <t>target="RFC8445" format="default"/>. </li> <li> If a newly formed pair has a local candidate whose type is server reflexive, the agentMUST<bcp14>MUST</bcp14> replace the local candidate with its base before completing the relevant redundancy tests.</t> <t></li> <li> The agent prunes redundant pairs by following the rules inSection 6.1.2.4 of<xreftarget='rfc5245bis'/>,target="RFC8445" format="default" sectionFormat="of" section="6.1.2.4"/> but checks existing pairs only if they have a state of Waiting or Frozen; this avoids removal of pairs for which connectivity checks are in flight (a state ofIn-Progress)In&nbhy;Progress) or for which connectivity checks have already yielded a definitive result (a state of Succeeded or Failed).</t> <t> If</li> <li> If, after completing the relevant redundancyteststests, thecheck listchecklist where the pair is to be added already contains the maximum number of candidate pairs (100 by default as per <xreftarget="rfc5245bis"/>),target="RFC8445" format="default"/>), the agentSHOULD<bcp14>SHOULD</bcp14> discard any pairs in the Failed state to make room for the new pair. If there are no such pairs, the agentSHOULD<bcp14>SHOULD</bcp14> discard a pair with a lower priority than the new pair in order to make room for the new pair, until the number of pairs is equal to the maximum number of pairs. This processing is consistent withSection 6.1.2.5 of<xreftarget='rfc5245bis'/>. </t> </list> </t>target="RFC8445" format="default" sectionFormat="of" section="6.1.2.5"/>. </li> </ol> </section> <sectiontitle='Receivinganchor="trickle-recv" numbered="true" toc="default"> <name>Receiving TrickledCandidates' anchor="trickle-recv">Candidates</name> <t> At any time during an ICE session, a Trickle ICE agent might receive new candidates from the remote agent, from which it will attempt to form a candidate pair; this works as described in the ICE specification <xreftarget='rfc5245bis'/>,target="RFC8445" format="default"/>, with the following provisos:<list style='numbers'> <t></t> <ol spacing="normal" type="1"> <li> The agent checks if any local candidates are currently known for this same stream and component. If not, the agent merely adds the new candidate to the list of remote candidates (without pairing it).</t> <t></li> <li> Otherwise, if the agent has already gathered one or more local candidates for this stream and component, it attempts to pair the new remote candidate as described in the ICE specification <xreftarget='rfc5245bis'/>. </t> <t>target="RFC8445" format="default"/>. </li> <li> If a newly formed pair has a local candidate whose type is server reflexive, the agentMUST<bcp14>MUST</bcp14> replace the local candidate with its base before completing the redundancy check in the next step.</t></li> <li> <t> The agent prunes redundant pairs as describedbelow,below but checks existing pairs only if they have a state of Waiting or Frozen; this avoids removal of pairs for which connectivity checks are in flight (a state of In-Progress) or for which connectivity checks have already yielded a definitive result (a state of Succeeded or Failed).<list style='letters'> <t></t> <ol spacing="normal" type="A"> <li> If the agent finds a redundancy between two pairs and one of those pairs contains a newly received remote candidate whose type is peer reflexive, the agentSHOULD<bcp14>SHOULD</bcp14> discard the pair containing that candidate, set the priority of the existing pair to the priority of the discarded pair, and re-sort thecheck list.checklist. (This policy helps to eliminate problems with remotepeer reflexivepeer-reflexive candidates for which a STUNbindingBinding request is received before signaling of the candidate is trickled to the receiving agent, such as a different view of pair priorities between the local agent and the remote agent,sincebecause the same candidate could be perceived as peer reflexive by one agent and as server reflexive by the other agent.)</t> <t></li> <li> The agent then applies the rules defined inSection 6.1.2.4 of<xreftarget='rfc5245bis'/>. </t> </list> </t> <t> Iftarget="RFC8445" format="default" sectionFormat="of" section="6.1.2.4"/>. </li> </ol> </li> <li> If, after completing the relevant redundancyteststests, thecheck listchecklist where the pair is to be added already contains the maximum number of candidate pairs (100 by default as per <xreftarget="rfc5245bis"/>),target="RFC8445" format="default"/>), the agentSHOULD<bcp14>SHOULD</bcp14> discard any pairs in the Failed state to make room for the new pair. If there are no such pairs, the agentSHOULD<bcp14>SHOULD</bcp14> discard a pair with a lower priority than the new pair in order to make room for the new pair, until the number of pairs is equal to the maximum number of pairs. This processing is consistent withSection 6.1.2.5 of<xreftarget='rfc5245bis'/>. </t> </list> </t>target="RFC8445" format="default" sectionFormat="of" section="6.1.2.5"/>. </li> </ol> </section> <sectiontitle='Insertinganchor="trickle-insert" numbered="true" toc="default"> <name>Inserting Trickled Candidate Pairs into aCheck List' anchor="trickle-insert">Checklist</name> <t> After a local agent has trickled a candidate and formed a candidate pair from that local candidate (<xreftarget='trickle-send'/>),target="trickle-send" format="default"/>), or after a remote agent has received a trickled candidate and formed a candidate pair from that remote candidate (<xreftarget='trickle-recv'/>),target="trickle-recv" format="default"/>), a Trickle ICE agent adds the new candidate pair to acheck listchecklist as defined in this section. </t> <t> As an aid to understanding the procedures defined in this section, consider the following tabular representation of allcheck listschecklists in an agent (note that initially for one of the foundations, i.e., f5, there are no candidate pairs): </t><t> <figure title="Example of Check List State" anchor="fig-checklist-0"> <artwork> <![CDATA[ +-----------------+------+------+------+------+------+ | | 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 | | | | | +-----------------+------+------+------+------+------+ ]]> </artwork> </figure> </t><table anchor="checklist_table"> <name>Example of Checklist State</name> <thead> <tr> <th></th> <th>f1</th> <th>f2</th> <th>f3</th> <th>f4</th> <th>f5</th> </tr> </thead> <tbody> <tr> <td>s1 (Audio.RTP)</td> <td>F</td> <td>F</td><td>F</td><td></td> <td/> </tr> <tr> <td>s2 (Audio.RTCP)</td> <td>F</td> <td>F</td><td>F</td><td>F</td><td/> </tr> <tr> <td>s3 (Video.RTP)</td> <td>F</td> <td></td><td> </td><td></td> <td/> </tr> <tr> <td>s4 (Video.RTCP)</td> <td>F</td> <td></td><td> </td><td> </td><td/> </tr> </tbody> </table> <t> Each row in the table represents a component for a given data stream (e.g., s1 and s2 might be the RTP andRTCPRTP Control Protocol (RTCP) components for audio) and thus a singlecheck listchecklist in thecheck listchecklist 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 notatenewly-addednewly added candidate pairs. </t> <t> When an agent commences ICE processing, in accordance withSection 6.1.2.6 of<xreftarget="rfc5245bis"/>,target="RFC8445" format="default" sectionFormat="of" section="6.1.2.6"/>, 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. </t><t> <figure title="Initial Check List State"<table anchor="fig-checklist-initial"><artwork> <![CDATA[ +-----------------+------+------+------+------+------+ | | 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 | | | | | +-----------------+------+------+------+------+------+ ]]> </artwork> </figure> </t><name>Initial Checklist State</name> <thead> <tr> <th></th> <th>f1</th> <th>f2</th> <th>f3</th> <th>f4</th> <th>f5</th> </tr> </thead> <tbody> <tr> <td>s1 (Audio.RTP)</td> <td>W</td> <td>W</td><td>W</td><td></td> <td/> </tr> <tr> <td>s2 (Audio.RTCP)</td> <td>F</td> <td>F</td><td>F</td><td>W</td><td/> </tr> <tr> <td>s3 (Video.RTP)</td> <td>F</td> <td></td><td> </td><td></td> <td/> </tr> <tr> <td>s4 (Video.RTCP)</td> <td>F</td> <td></td><td> </td><td> </td><td/> </tr> </tbody> </table> <t> Then, as the checks proceed (seeSection 7.2.5.4 of<xreftarget="rfc5245bis"/>),target="RFC8445" format="default" sectionFormat="of" section="7.2.5.4"/>), for each pair that enters the Succeeded state (denoted here by "S"), 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 thepairpairs in column 1, rows 2, 3, and 4). </t><t> <figure title="Check List<table anchor="fig-checklist-succeeded"> <name>Checklist State with Succeeded CandidatePair" anchor="fig-checklist-succeeded"> <artwork> <![CDATA[ +-----------------+------+------+------+------+------+ | | 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 | | | | | +-----------------+------+------+------+------+------+ ]]> </artwork> </figure> </t>Pair</name> <thead> <tr> <th></th> <th>f1</th> <th>f2</th> <th>f3</th> <th>f4</th> <th>f5</th> </tr> </thead> <tbody> <tr> <td>s1 (Audio.RTP)</td> <td>S</td> <td>W</td><td>W</td><td></td> <td/> </tr> <tr> <td>s2 (Audio.RTCP)</td> <td>W</td> <td>F</td><td>F</td><td>W</td><td/> </tr> <tr> <td>s3 (Video.RTP)</td> <td>W</td> <td></td><td> </td><td></td> <td/> </tr> <tr> <td>s4 (Video.RTCP)</td> <td>W</td> <td></td><td> </td><td> </td><td/> </tr> </tbody> </table> <t> Trickle ICE preserves all of these rules as they apply to "static"check listchecklist 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. </t> <t> Of course, the major difference with Trickle ICE is thatcheck listchecklist 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. </t> <t> 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 withSection 6.1.2.6 of<xreftarget="rfc5245bis"/>.target="RFC8445" format="default" sectionFormat="of" section="6.1.2.6"/>. </t><t> <figure title="Check List<table anchor="fig-checklist-rule1"> <name>Checklist State with Newly Formed Pair, Rule1" anchor="fig-checklist-rule1"> <artwork> <![CDATA[ +-----------------+------+------+------+------+------+ | | 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 | | | | | +-----------------+------+------+------+------+------+ ]]> </artwork> </figure> </t>1</name> <thead> <tr> <th></th> <th>f1</th> <th>f2</th> <th>f3</th> <th>f4</th> <th>f5</th> </tr> </thead> <tbody> <tr> <td>s1 (Audio.RTP)</td> <td>S</td> <td>W</td> <td>W</td> <td></td> <td>^W^</td> </tr> <tr> <td>s2 (Audio.RTCP)</td> <td>W</td> <td>F</td><td>F</td><td>W</td><td/> </tr> <tr> <td>s3 (Video.RTP)</td> <td>W</td> <td></td><td> </td><td></td> <td/> </tr> <tr> <td>s4 (Video.RTCP)</td> <td>W</td> <td></td><td> </td><td> </td><td/> </tr> </tbody> </table> <t> 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 withSection 7.2.5.3.3 of<xreftarget="rfc5245bis"/>.target="RFC8445" format="default" sectionFormat="of" section="7.2.5.3.3"/>. </t><t> <figure title="Check List<table anchor="fig-checklist-rule2"> <name>Checklist State with Newly Formed Pair, Rule2" anchor="fig-checklist-rule2"> <artwork> <![CDATA[ +-----------------+------+------+------+------+------+ | | 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 | | | | | +-----------------+------+------+------+------+------+ ]]> </artwork> </figure> </t>2</name> <thead> <tr> <th></th> <th>f1</th> <th>f2</th> <th>f3</th> <th>f4</th> <th>f5</th> </tr> </thead> <tbody> <tr> <td>s1 (Audio.RTP)</td> <td>S</td> <td>W</td> <td>W</td> <td></td> <td>S</td> </tr> <tr> <td>s2 (Audio.RTCP)</td> <td>W</td> <td>F</td><td>F</td><td>W</td> <td>^W^</td> </tr> <tr> <td>s3 (Video.RTP)</td> <td>W</td> <td></td><td> </td><td></td> <td/> </tr> <tr> <td>s4 (Video.RTCP)</td> <td>W</td> <td></td><td> </td><td> </td><td/> </tr> </tbody> </table> <t> 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. </t><t> <figure title="Check List<table anchor="fig-checklist-rule3"> <name>Checklist State with Newly Formed Pair, Rule3" anchor="fig-checklist-rule3"> <artwork> <![CDATA[ +-----------------+------+------+------+------+------+ | | 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 | | | | | +-----------------+------+------+------+------+------+ ]]> </artwork> </figure> </t> </section> <section title='Generating3</name> <thead> <tr> <th></th> <th>f1</th> <th>f2</th> <th>f3</th> <th>f4</th> <th>f5</th> </tr> </thead> <tbody> <tr> <td>s1 (Audio.RTP)</td> <td>S</td> <td>W</td> <td>W</td> <td></td> <td>S</td> </tr> <tr> <td>s2 (Audio.RTCP)</td> <td>W</td> <td>F</td><td>F</td><td>W</td> <td>W</td> </tr> <tr> <td>s3 (Video.RTP)</td> <td>W</td> <td></td><td>^F^</td><td></td> <td/> </tr> <tr> <td>s4 (Video.RTCP)</td> <td>W</td> <td></td><td> </td><td> </td><td/> </tr> </tbody> </table> </section> <section anchor="end-of-candidates.send" numbered="true" toc="default"> <name>Generating an End-of-CandidatesIndication' anchor="end-of-candidates.send">Indication</name> <t> 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 indicationMUST<bcp14>MUST</bcp14> specify the generation (Username Fragment and Passwordcombination)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:<list style='symbols'> <t>As</t> <ul spacing="normal"> <li>As part of an initiation request (which would typically be the case with the initial ICE description for halftrickle)</t> <t>Alongtrickle)</li> <li>Along with the last candidate an agent can send for astream</t> <t>Asstream</li> <li>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 gatheringcandidates)</t> </list> </t>candidates)</li> </ul> <t> 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:<list style='symbols'> <t></t> <ul spacing="normal"> <li> A controlled Trickle ICE agentSHOULD<bcp14>SHOULD</bcp14> 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.</t> <t></li> <li> A controlling agentMAY<bcp14>MAY</bcp14> conclude ICE processing prior to conveying end-of-candidates indications for all streams. However, it isRECOMMENDED<bcp14>RECOMMENDED</bcp14> for a controlling agent to convey end-of-candidates indications whenever possible for the sake of consistency and to keep middleboxes and controlled agents up-to-date on the state of ICE processing.</t> </list> </t></li> </ul> <t> 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. </t> <t> An agentMAY<bcp14>MAY</bcp14> 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 agentMUST NOT<bcp14>MUST NOT</bcp14> convey any more candidates after it has conveyed an end-of-candidates indication. </t> <t> When performing half trickle, an agentSHOULD<bcp14>SHOULD</bcp14> 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). </t> <t> After an agent conveys the end-of-candidates indication, it will update the state of the correspondingcheck listchecklist as explained in <xreftarget="checks"/>.target="checks" format="default"/>. Past that point, an agentMUST NOT<bcp14>MUST NOT</bcp14> trickle any new candidates within this ICE session. Therefore, adding new candidates to the negotiation is possible only through an ICE restart (see <xreftarget='subsequent'/>).target="subsequent" format="default"/>). </t> <t> 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 processingMAY<bcp14>MAY</bcp14> still conclude even if end-of-candidates indications have not been received for all streams. In all cases, an agentMUST NOT<bcp14>MUST NOT</bcp14> trickle any new candidates within an ICE session after nomination of a candidate pair as described inSection 8.1.1 of<xreftarget='rfc5245bis'/>.target="RFC8445" format="default" sectionFormat="of" section="8.1.1"/>. </t> </section> <sectiontitle='Receivinganchor="end-of-candidates.recv" numbered="true" toc="default"> <name>Receiving an End-of-CandidatesIndication' anchor="end-of-candidates.recv">Indication</name> <t> Receiving an end-of-candidates indication enables an agent to updatecheck listchecklist 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 butit involves the use ofuses a lower-preferencetransportstransport such as TURN. In such situations, an implementationMAY<bcp14>MAY</bcp14> choose to wait and see if higher-priority candidates are received; in thiscasecase, the end-of-candidates indication provides a notification that such candidates are not forthcoming. </t> <t> When an agent receives an end-of-candidates indication for a specific data stream, it will update the state of the relevantcheck listchecklist as per <xreftarget="checks"/>target="checks" format="default"/> (which might lead to somecheck listschecklists being marked as Failed). If thecheck listchecklist is still in the Running state after the update, the agent willpersist the factnote that an end-of-candidates indication has been received and take it into account in future updates to thecheck list.checklist. </t> <t> After an agent has received an end-of-candidates indication, itMUST<bcp14>MUST</bcp14> ignore any newly received candidates for that data stream or data session. </t> </section> <sectiontitle='Subsequentanchor="subsequent" numbered="true" toc="default"> <name>Subsequent Exchanges and ICERestarts' anchor="subsequent">Restarts</name> <t> Before conveying an end-of-candidates indication, either agentMAY<bcp14>MAY</bcp14> convey subsequent candidate information at any time allowed by the using protocol. When this happens, agents will use<xref target="rfc5245bis"/>semantics from <xref target="RFC8445" format="default"/> (e.g., checking of the Username Fragment and Password combination) to determine whether or not the new candidate information requires an ICE restart. </t> <t> If an ICE restart occurs, the agents can assume that Trickle ICE is still supported if support was determinedpreviously, and thuspreviously; thus, they 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. </t> </section> <sectiontitle='Half Trickle' anchor="half-trickle">anchor="half-trickle" numbered="true" toc="default"> <name>Half Trickle</name> <t> 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 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 isconfirmedconfirmed, then the initiator can choose to trickle additional candidates before it conveys an end-of-candidates indication. </t> <t> Thehalf tricklehalf-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 descriptioncontaincontains 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. </t> <t> 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 (see <xreftarget='subsequent'/>).target="subsequent" format="default"/>). </t> <t> 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 uponuser interfaceuser-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. </t> <t> 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. </t> </section> <sectiontitle='Preservingnumbered="true" toc="default"> <name>Preserving Candidate Orderwhile Trickling'>While Trickling</name> <t> 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 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. </t> <t> To achieve this, when trickling candidates, agentsSHOULD<bcp14>SHOULD</bcp14> respect the order of components as reflected by their component IDs; that is, candidates for a given componentSHOULD NOT<bcp14>SHOULD NOT</bcp14> be conveyed prior to candidates for a component with a lower ID number within the same foundation. In addition, candidatesSHOULD<bcp14>SHOULD</bcp14> be paired, following the procedures in <xreftarget='trickle-insert'/>,target="trickle-insert" format="default"/>, in the same order they are conveyed. </t> <t> For example, the following SDP description contains two components (RTP and RTCP) and two foundations (host and server reflexive):<figure> <artwork> <![CDATA[</t> <sourcecode type="sdp"><![CDATA[ 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]]> </artwork> </figure>]]></sourcecode> <t> For this candidateinformationinformation, the RTCP host candidate would not be conveyed prior to the RTP host candidate.SimilarlySimilarly, the RTPserver reflexiveserver-reflexive candidate would be conveyed together with or prior to the RTCPserver reflexiveserver-reflexive candidate. </t> </section> <sectiontitle='Requirementsanchor="reqs" numbered="true" toc="default"> <name>Requirements for UsingProtocols' anchor="reqs">Protocols</name> <t> In order to fully enable the use of Trickle ICE, this specification defines the following requirements for using protocols.<list style='symbols'> <t></t> <ul spacing="normal"> <li> A using protocolSHOULD<bcp14>SHOULD</bcp14> provide a way for parties to advertise and discover support for Trickle ICE before an ICE session begins (see <xreftarget='support'/>). </t> <t>target="support" format="default"/>). </li> <li> A using protocolMUST<bcp14>MUST</bcp14> provide methods for incrementally conveying (i.e., "trickling") additional candidates after conveying the initial ICE description (see <xreftarget='trickle-send'/>). </t> <t>target="trickle-send" format="default"/>). </li> <li> A using protocolMUST<bcp14>MUST</bcp14> deliver each trickled candidate or end-of-candidates indication exactly once and in the same order it was conveyed (see <xreftarget='trickle-send'/>). </t> <t>target="trickle-send" format="default"/>). </li> <li> A using protocolMUST<bcp14>MUST</bcp14> provide a mechanism for both parties to indicate and agree on the ICE session in force (see <xreftarget='trickle-send'/>). </t> <t>target="trickle-send" format="default"/>). </li> <li> A using protocolMUST<bcp14>MUST</bcp14> provide a way for parties to communicate the end-of-candidates indication, whichMUST<bcp14>MUST</bcp14> specify the particular ICE session to which the indication applies (see <xreftarget='end-of-candidates.send'/>). </t> </list> </t>target="end-of-candidates.send" format="default"/>). </li> </ul> </section> <sectiontitle='IANA Considerations'>numbered="true" toc="default"> <name>IANA Considerations</name> <t> IANAis requested to registerhas registered the following ICE option in the "ICE Options"sub-registrysubregistry of the "Interactive Connectivity Establishment (ICE) registry", following the procedures defined in <xreftarget='RFC6336'/>.target="RFC6336" format="default"/>. </t><t> <list style='hanging'> <t hangText="ICE Option:">trickle</t> <t hangText="Contact:">IESG, iesg@ietf.org</t> <t hangText="Change control:">IESG</t> <t hangText="Description:"><dl newline="false" spacing="normal"> <dt>ICE Option:</dt> <dd>trickle</dd> <dt>Contact:</dt> <dd>IESG <iesg@ietf.org></dd> <dt>Change controller:</dt> <dd>IESG</dd> <dt>Description:</dt> <dd> An ICE option of"trickle"'trickle' indicates support for incremental communication of ICE candidates.</t> <t hangText="Reference:">RFC XXXX</t> </list> </t></dd> <dt>Reference:</dt> <dd>RFC 8838</dd> </dl> </section> <sectiontitle='Security Considerations'>numbered="true" toc="default"> <name>Security Considerations</name> <t> This specification inherits most of its semantics from <xreftarget="rfc5245bis"/>target="RFC8445" format="default"/>, and as aresultresult, all security considerations described there apply to Trickle ICE. </t> <t> If the privacy implications of revealing host addresses on an endpoint device are a concern(see(see, forexampleexample, the discussion in <xreftarget='I-D.ietf-rtcweb-ip-handling'/>target="RFC8828" format="default"/> and inSection 19 of<xreftarget="rfc5245bis"/>),target="RFC8445" section="19" sectionFormat="of"/>), agents can generate ICE descriptions that contain no candidates and then only trickle candidates that do not reveal host addresses (e.g., relayed candidates). </t> </section><section title='Acknowledgements'> <t> 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, Brandon Williams, and Dale Worley</middle> <back> <references> <name>References</name> <references> <name>Normative References</name> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/> <!--note: rfc5245bis is now RFC 8445--> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8445.xml"/> </references> <references> <name>Informative References</name> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.1918.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.3261.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.3264.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.4566.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.4787.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.5389.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.6120.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.6336.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8656.xml"/> <!--draft-ietf-mmusic-trickle-ice-sip-18 in C238 --> <reference anchor="RFC8840" target="https://www.rfc-editor.org/info/rfc8840"> <front> <title>A Session Initiation Protocol (SIP) Usage fortheir reviews and suggestions on improving this document. Sarah Banks, Roni Even, and David Mandelberg completed opsdir, genart, and security reviews, respectively. Thanks also to Ari Keranen and Peter Thatcher in their role as chairs, and Ben Campbell in his role as responsible Area Director. </t> </section> </middle> <back> <references title='Normative References'> <?rfc include="reference.RFC.2119"?> <reference anchor='rfc5245bis'> <front> <title>Interactive Connectivity Establishment (ICE): A Protocol for Network Address Translator (NAT) Traversal</title> <author initials='A' surname='Keranen' fullname='Ari Keranen'> <organization /> </author> <author initials='C' surname='Holmberg' fullname='Christer Holmberg'> <organization /> </author> <author initials='J' surname='Rosenberg' fullname='Jonathan Rosenberg'> <organization /> </author> <date month='March' day='8' year='2018' /> <abstract><t>This document describes a protocol for Network Address Translator (NAT) traversalIncremental Provisioning of Candidates forUDP-based multimedia. This protocol is calledthe Interactive Connectivity Establishment(ICE). ICE makes use of the Session Traversal Utilities for NAT (STUN) protocol and its extension, Traversal Using Relay NAT (TURN). This document obsoletes RFC 5245.</t></abstract> </front> <seriesInfo name='Internet-Draft' value='draft-ietf-ice-rfc5245bis-20' /> <format type='TXT' target='http://www.ietf.org/internet-drafts/draft-ietf-ice-rfc5245bis-20.txt' /> </reference> </references> <references title='Informative References'> <?rfc include="reference.RFC.1918"?> <?rfc include="reference.RFC.3261"?> <?rfc include="reference.RFC.3264"?> <?rfc include="reference.RFC.4566"?> <?rfc include="reference.RFC.4787"?> <?rfc include="reference.RFC.5389"?> <?rfc include="reference.RFC.5766"?> <?rfc include="reference.RFC.6120"?> <?rfc include="reference.RFC.6336"?> <reference anchor='I-D.ietf-mmusic-trickle-ice-sip'> <front> <title>A Session Initiation Protocol (SIP) usage for Trickle ICE</title>(Trickle ICE)</title> <authorinitials='E' surname='Ivov' fullname='Emil Ivov'> <organization />initials="E" surname="Ivov" fullname="Emil Ivov"> <organization/> </author> <authorinitials='T' surname='Stach' fullname='Thomas Stach'> <organization />initials="T" surname="Stach" fullname="Thomas Stach"> <organization/> </author> <authorinitials='E' surname='Marocco' fullname='Enrico Marocco'> <organization />initials="E" surname="Marocco" fullname="Enrico Marocco"> <organization/> </author> <authorinitials='C' surname='Holmberg' fullname='Christer Holmberg'> <organization />initials="C" surname="Holmberg" fullname="Christer Holmberg"> <organization/> </author> <datemonth='February' day='24' year='2018' /> <abstract><t>The Interactive Connectivity Establishment (ICE) protocol describes a Network Address Translator (NAT) traversal mechanism for UDP-based multimedia sessions established with the Offer/Answer model. The ICE extension for Incremental Provisioning of Candidates (Trickle ICE) defines a mechanism that allows ICE agents to shorten session establishment delays by making the candidate gathering and connectivity checking phases of ICE non-blocking and by executing them in parallel. This document defines usage semantics for Trickle ICE with the Session Initiation Protocol (SIP).</t></abstract>month="June" year="2018"/> </front> <seriesInfoname='Internet-Draft' value='draft-ietf-mmusic-trickle-ice-sip-14' /> <format type='TXT' target='http://www.ietf.org/internet-drafts/draft-ietf-mmusic-trickle-ice-sip-14.txt' />name="DOI" value="10.17487/RFC8840"/> <seriesInfo name="RFC" value="8840"/> </reference> <!--draft-ietf-rtcweb-ip-handling-09 in C238 --> <referenceanchor='I-D.ietf-rtcweb-ip-handling'>anchor="RFC8828" target="https://www.rfc-editor.org/info/rfc8828"> <front> <title>WebRTC IP Address Handling Requirements</title> <authorinitials='J' surname='Uberti' fullname='Justin Uberti'> <organization />initials="J" surname="Uberti" fullname="Justin Uberti"> <organization/> </author> <authorinitials='G' surname='Shieh' fullname='Guo-wei Shieh'> <organization />initials="G" surname="Shieh" fullname="Guo-wei Shieh"> <organization/> </author> <datemonth='March' day='1' year='2018' /> <abstract><t>This document provides information and requirements for how IP addresses should be handled by WebRTC implementations.</t></abstract>month="May" year="2020"/> </front> <seriesInfoname='Internet-Draft' value='draft-ietf-rtcweb-ip-handling-06' /> <format type='TXT' target='http://www.ietf.org/internet-drafts/draft-ietf-rtcweb-ip-handling-06.txt' />name="DOI" value="10.17487/RFC8828"/> <seriesInfo name="RFC" value="8828"/> </reference> <reference anchor="XEP-0176"> <front> <title>XEP-0176: Jingle ICE-UDP Transport Method</title> <seriesInfo name="XMPP Standards Foundation," value="XEP-0176"/> <authorinitials='J.' surname='Beda' fullname='Joe Beda'>initials="J." surname="Beda" fullname="Joe Beda"> <organizationabbrev='Google'>Google</organization>abbrev="Google">Google</organization> </author> <authorinitials='S.' surname='Ludwig' fullname='Scott Ludwig'>initials="S." surname="Ludwig" fullname="Scott Ludwig"> <organizationabbrev='Google'>Google</organization>abbrev="Google">Google</organization> </author> <authorinitials='P.' surname='Saint-Andre' fullname='Peter Saint-Andre'>initials="P." surname="Saint-Andre" fullname="Peter Saint-Andre"> </author> <authorinitials='J.' surname='Hildebrand' fullname='Joe Hildebrand'>initials="J." surname="Hildebrand" fullname="Joe Hildebrand"> <organizationabbrev='Cisco'>Cisco</organization>abbrev="Cisco">Cisco</organization> </author> <authorinitials='S.' surname='Egan' fullname='Sean Egan'>initials="S." surname="Egan" fullname="Sean Egan"> <organizationabbrev='Google'>Googleabbrev="Google">Google </organization> </author> <authorinitials='R.' surname='McQueen' fullname='Robert McQueen'>initials="R." surname="McQueen" fullname="Robert McQueen"> <organizationabbrev='Collabora'>Collabora</organization>abbrev="Collabora">Collabora</organization> </author> <date month="June"year="2009" />year="2009"/> </front><seriesInfo name="XEP" value="XEP-0176" /></reference> <reference anchor="XEP-0030"> <front> <title>XEP-0030: Service Discovery</title> <seriesInfo name="XMPP Standards Foundation," value="XEP-0030"/> <authorinitials='J.' surname='Hildebrand' fullname='Joe Hildebrand'>initials="J." surname="Hildebrand" fullname="Joe Hildebrand"> <organizationabbrev='Cisco'>Cisco</organization>abbrev="Cisco">Cisco</organization> </author> <authorinitials='P.' surname='Millard' fullname='Peter Millard'>initials="P." surname="Millard" fullname="Peter Millard"> </author> <authorinitials='R.' surname='Eatmon' fullname='Ryan Eatmon'>initials="R." surname="Eatmon" fullname="Ryan Eatmon"> </author> <authorinitials='P.' surname='Saint-Andre' fullname='Peter Saint-Andre'>initials="P." surname="Saint-Andre" fullname="Peter Saint-Andre"> </author> <date month="June"year="2008" />year="2008"/> </front><seriesInfo name="XEP" value="XEP-0030" /></reference> </references> </references> <sectiontitle='Interactionanchor="interaction" numbered="true" toc="default"> <name>Interaction with RegularICE' anchor='interaction'>ICE</name> <t> 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 <xreftarget="rfc5245bis"/>target="RFC8445" format="default"/> does not by itself supporttrickleTrickle ICE. This section describes how trickling of candidates interacts with ICE. </t> <t> <xreftarget="rfc5245bis"/>target="RFC8445" format="default"/> describes the conditions required to updatecheck listschecklists and timer states while an ICE agent is in the Running state. These conditions are verified upon transactioncompletioncompletion, and one of them stipulates that: </t><t> <list style='empty'> <t><ul empty="true" spacing="normal"> <li> If there is not a pair in the valid list for each component of the data stream, the state of thecheck listchecklist is set to Failed.</t> </list> </t></li> </ul> <t> This could be a problem and cause ICE processing to fail prematurely in a number of scenarios. Consider the following case: </t><t> <list style='numbers'> <t><ol spacing="normal" type="1"> <li> Alice and Bob are both located in different networks with Network Address Translation (NAT). Alice and Bob themselves have differentaddressaddresses, but both networks use the same private internet block (e.g., the "20-bit block" 172.16/12 specified in <xreftarget="RFC1918"/>). </t> <t>target="RFC1918" format="default"/>). </li> <li> Alice conveys to Bob the candidate172.16.0.1172.16.0.1, which also happens to correspond to an existing host on Bob's network.</t> <t></li> <li> Bob creates acheck list consisting solely of 172.16.0.1candidate pair from his host candidate and 172.16.0.1, puts this one pair into a checklist, and starts checks.</t> <t></li> <li> These checks reach the host at 172.16.0.1 in Bob's network, which responds with an ICMP "port unreachable" error; per <xreftarget="rfc5245bis"/>target="RFC8445" format="default"/>, Bob marks the transaction as Failed.</t> </list></li> </ol> <t> At thispointpoint, thecheck listchecklist only contains a Failedcandidatespair, and the valid list is empty. This causes the data stream and potentially all ICE processing to fail, even thoughifTrickle ICE agentscouldcan subsequently convey candidates thatwould cause previously empty check lists to become non-empty.could succeed. </t> <t> A similar race condition would occur if the initial ICE description from Alicecontaincontains 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). </t> <t> Another potential problem could arise when anon-tricklenon-Trickle ICE implementation initiates an interaction with a Trickle ICE implementation. Consider the following case:<list style='numbers'> <t></t> <ol spacing="normal" type="1"> <li> Alice's client has a non-Trickle ICE implementation.</t> <t></li> <li> Bob's client has support for Trickle ICE.</t> <t></li> <li> Alice and Bob are behind NATs with address-dependent filtering <xreftarget="RFC4787"/>. </t> <t>target="RFC4787" format="default"/>. </li> <li> Bob has two STUNserversservers, but one of them is currently unreachable.</t> </list> </t></li> </ol> <t> After Bob's agent receives Alice's initial ICEdescriptiondescription, 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. </t> </section> <sectiontitle='Interactionnumbered="true" toc="default"> <name>Interaction withICE Lite'>ICE-Lite</name> <t> The behavior ofICE liteICE-lite agents that are capable of Trickle ICE does not require any particular rules other than those already defined in this specification and <xreftarget="rfc5245bis"/>.target="RFC8445" format="default"/>. This section is hence provided only for informational purposes. </t> <t> AnICE liteICE-lite agent would generate candidate information as per <xreftarget="rfc5245bis"/>target="RFC8445" format="default"/> 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. </t> <t> 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 anICE liteICE-lite implementation, the initiator can choose to not trickle any additional candidates. The same is also true in the case when theICE liteICE-lite agent initiates the interaction and the full ICE agent is the responder. In thesecasescases, the connectivity checks would be enough for theICE liteICE-lite implementation to discover all potentially useful candidates as peer reflexive. The following example illustrates one such ICE session using SDP syntax: </t> <figuretitle="Example "anchor="fig-ice-lite"><artwork> <![CDATA[ ICE Lite<name>Example</name> <artwork name="" type="" align="left" alt=""><![CDATA[ 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 ===========>|]]> </artwork>]]></artwork> </figure> <t> In addition to reducing signalingtraffictraffic, this approach also removes the need to discover STUNbindingsBindings or make TURN allocations, which can considerably lighten ICE processing. </t> </section> <sectiontitle='Changes from Earlier Versions'> <t> Note to the RFC Editor: please remove this section prior to publication as an RFC. </t> <section title='Changes from draft-ietf-ice-trickle-20'> <t> <list style='symbols'>numbered="false" toc="default"> <name>Acknowledgements</name> <t>Slight correctionsThe authors would like tohanlding of peer reflexive candidates. </t> <t> Wordsmithing in a few sections. </t> </list> </t> </section> <section title='Changes from draft-ietf-ice-trickle-19'> <t> <list style='symbols'> <t> Further clarified handling of remote peer reflexive candidates. </t> <t> To improve readibility, renamed and restructured some sections and subsections, and modified some wording. </t> </list> </t> </section> <section title='Changes from draft-ietf-ice-trickle-18'> <t> <list style='symbols'> <t> Cleaned up pairing and redundancy checking rulesthank <contact fullname="Bernard Aboba"/>, <contact fullname="Flemming Andreasen"/>, <contact fullname="Rajmohan Banavi"/>, <contact fullname="Taylor Brandstetter"/>, <contact fullname="Philipp Hancke"/>, <contact fullname="Christer Holmberg"/>, <contact fullname="Ari Keränen"/>, <contact fullname="Paul Kyzivat"/>, <contact fullname="Jonathan Lennox"/>, <contact fullname="Enrico Marocco"/>, <contact fullname="Pal Martinsen"/>, <contact fullname="Nils Ohlmeier"/>, <contact fullname="Thomas Stach"/>, <contact fullname="Peter Thatcher"/>, <contact fullname="Martin Thomson"/>, <contact fullname="Brandon Williams"/>, and <contact fullname="Dale Worley"/> fornewly discovered candidates per IESG feedbacktheir reviews andWG discussion. </t> <t> Improved wording in half trickle section. </t> <t> Changed "not more than once" to "exactly once". </t> <t> Changed NAT examples backsuggestions on improving this document. <contact fullname="Sarah Banks"/>, <contact fullname="Roni Even"/>, and <contact fullname="David Mandelberg"/> completed OPSDIR, GenART, and security reviews, respectively. Thanks also toIPv4. </t> </list> </t> </section> <section title='Changes from draft-ietf-ice-trickle-17'> <t> <list style='symbols'> <t> Simplified the rules for inserting a new pairAri Keranen and Peter Thatcher ina check list. </t> <t> Clarified it is not allowed to nominate a candidate pair after a pair has already been nominated (a.k.a. renomination or continuous nomination). </t> <t> Removed some text that referenced older versions of rfc5245bis. </t> <t> Removed some text that duplicated conceptstheir role as chairs andprocedures specifiedBen Campbell inrfc5245bis. </t> <t> Removed the ill-defined concept of stream order. </t> <t> Shortened the introduction. </t> </list> </t> </section> <section title='Changes from draft-ietf-ice-trickle-16'> <t> <list style='symbols'> <t> Made "ufrag" terminology consistent with 5245bis. </t> <t> Applied in-order delivery rule to end-of-candidates indication. </t> </list> </t> </section> <section title='Changes from draft-ietf-ice-trickle-15'> <t> <list style='symbols'> <t> Adjustments to address AD review feedback. </t> </list> </t> </section> <section title='Changes from draft-ietf-ice-trickle-14'> <t> <list style='symbols'> <t> Minor modifications to track changes to ICE core. </t> </list>his role as responsible Area Director. </t></section> <section title='Changes from draft-ietf-ice-trickle-13'> <t> <list style='symbols'> <t> 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. </t> </list> </t> </section> <section title='Changes from draft-ietf-ice-trickle-12'> <t> <list style='symbols'> <t> Specified that the end-of-candidates indication must include the generation (ufrag/pwd) to enable association with a particular ICE session. </t> <t> Further editorial fixes to address WGLC feedback. </t> </list> </t> </section> <section title='Changes from draft-ietf-ice-trickle-11'> <t> <list style='symbols'> <t> Editorial and terminological fixes to address WGLC feedback. </t> </list> </t> </section> <section title='Changes from draft-ietf-ice-trickle-10'> <t> <list style='symbols'> <t> Minor editorial fixes. </t> </list> </t> </section> <section title='Changes from draft-ietf-ice-trickle-09'> <t> <list style='symbols'> <t> Removed immediate unfreeze upon Fail. </t> <t> Specified MUST NOT regarding ice-options. </t> <t> Changed terminology regarding initial ICE parameters to avoid implementer confusion. </t> </list> </t> </section> <section title='Changes from draft-ietf-ice-trickle-08'> <t> <list style='symbols'> <t> Reinstated text about in-order processing of messages as a requirement for signaling protocols. </t> <t> Added IANA registration template for ICE option. </t> <t> Corrected Case 3 rule in Section 8.1.1 to ensure consistency with regular ICE rules. </t> <t> Added tabular representations to Section 8.1.1 in order to illustrate the new pair rules. </t> </list> </t> </section> <section title='Changes from draft-ietf-ice-trickle-07'> <t> <list style='symbols'> <t> Changed "ICE description" to "candidate information" for consistency with 5245bis. </t> </list> </t> </section> <section title='Changes from draft-ietf-ice-trickle-06'> <t> <list style='symbols'> <t> Addressed editorial feedback from chairs' review. </t> <t> Clarified terminology regarding generations. </t> </list> </t> </section> <section title='Changes from draft-ietf-ice-trickle-05'> <t> <list style='symbols'> <t> Rewrote the text on inserting a new pair into a check list. </t> </list> </t> </section> <section title='Changes from draft-ietf-ice-trickle-04'> <t> <list style='symbols'> <t> Removed dependency on SDP and offer/answer model. </t> <t> Removed mentions of aggressive nomination, since it is deprecated in 5245bis. </t> <t> Added section on requirements for signaling protocols. </t> <t> Clarified terminology. </t> <t> Addressed various WG feedback. </t> </list> </t> </section> <section title='Changes from draft-ietf-ice-trickle-03'> <t> <list style='symbols'> <t> Provided more detailed description of unfreezing behavior, specifically how to replace pre-existing peer-reflexive candidates with higher-priority ones received via trickling. </t> </list> </t> </section> <section title='Changes from draft-ietf-ice-trickle-02'> <t> <list style='symbols'> <t> Adjusted unfreezing behavior when there are disparate foundations. </t> </list> </t> </section> <section title='Changes from draft-ietf-ice-trickle-01'> <t> <list style='symbols'> <t> Changed examples to use IPv6. </t> </list> </t> </section> <section title='Changes from draft-ietf-ice-trickle-00'> <t> <list style='symbols'> <t> Removed dependency on SDP (which is to be provided in a separate specification). </t> <t> Clarified text about the fact that a check list can be empty if no candidates have been sent or received yet. </t> <t> 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. </t> <t> Removed open issues list because it was out of date. </t> <t> Completed a thorough copy edit. </t> </list> </t> </section> <section title='Changes from draft-mmusic-trickle-ice-02'> <t> <list style='symbols'> <t> Addressed feedback from Rajmohan Banavi and Brandon Williams. </t> <t> Clarified text about determining support and about how to proceed if it can be determined that the answering agent does not support Trickle ICE. </t> <t> Clarified text about check list and timer updates. </t> <t> Clarified when it is appropriate to use half trickle or to send no candidates in an offer or answer. </t> <t> Updated the list of open issues. </t> </list> </t> </section> <section title='Changes from draft-ivov-01 and draft-mmusic-00'> <t> <list style='symbols'> <t> Added a requirement to trickle candidates by order of components to avoid deadlocks in the unfreezing algorithm. </t> <t> 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. </t> <t> Limit the number of pairs to 100 to comply with 5245. </t> <t> 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. </t> <t> Added transport expectations for trickled candidates as per Dale Worley's recommendation. </t> </list> </t> </section> <section title='Changes from draft-ivov-00'> <t> <list style='symbols'> <t> 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. </t> <t> 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. </t> <t> 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. </t> <t> 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). </t> <t> It is now mandatory to use MID when trickling candidates and using m-line indexes is no longer allowed. </t> <t> 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). </t> <t> 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. </t> <t> Added more terminology, including trickling, trickled candidates, half trickle, full trickle, </t> <t> Added a reference to the SIP usage for Trickle ICE as requested at the Boston interim. </t> </list> </t> </section> <section title='Changes from draft-rescorla-01'> <t> <list style='symbols'> <t> 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. </t> <t> Added SDP specification for trickled candidates, the trickle option and 0.0.0.0 addresses in m-lines, and end-of-candidates. </t> <t> 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. </t> <t> 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. </t> <t> Added a short section about subsequent offer/answer exchanges. </t> <t> Added a short section about interactions with ICE Lite implementations. </t> <t> Added two new entries to the open issues section. </t> </list> </t> </section> <section title='Changes from draft-rescorla-00'> <t> <list style='symbols'> <t> Relaxed requirements about verifying support following a discussion on MMUSIC. </t> <t> Introduced ICE descriptions in order to remove ambiguous use of 3264 language and inappropriate references to offers and answers. </t> <t> Removed inappropriate assumption of adoption by RTCWEB pointed out by Martin Thomson. </t> </list> </t> </section></section> </back> </rfc>