idnits 2.17.1 draft-ietf-ice-pac-00.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- -- The draft header indicates that this document updates RFC8445, but the abstract doesn't seem to mention this, which it should. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'MUST not' in this paragraph: While the timer is running, if a checklist has no pairs left to check, i.e., there are no pairs that are not in the failed state, the ICE agent MUST not conclude that ICE processing has failed, and MUST wait for the timer to elapse before doing so. -- The document date (March 26, 2019) is 1856 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) No issues found here. Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 ICE Working Group C. Holmberg 3 Internet-Draft Ericsson 4 Updates: 8445 (if approved) J. Uberti 5 Intended status: Standards Track Google 6 Expires: September 27, 2019 March 26, 2019 8 Interactive Connectivity Establishment Patiently Awaiting Connectivity 9 (ICE PAC) 10 draft-ietf-ice-pac-00 12 Abstract 14 During the process of creating a peer-to-peer connection, ICE 15 implementations can encounter situations where they have no candidate 16 pairs to check, and, as a result, conclude that ICE processing has 17 failed. However, because additional candidate pairs can be 18 discovered during ICE processing, declaring failure at this point may 19 be premature. This document discusses when these situations can 20 occur and proposes a way to avoid premature failure. 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on September 27, 2019. 39 Copyright Notice 41 Copyright (c) 2019 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3 58 3. Relevant Scenarios . . . . . . . . . . . . . . . . . . . . . 3 59 3.1. No Candidates From Peer . . . . . . . . . . . . . . . . . 3 60 3.2. All Candidates Discarded . . . . . . . . . . . . . . . . 3 61 3.3. Immediate Candidate Pair Failure . . . . . . . . . . . . 4 62 4. Update to RFC 8445 . . . . . . . . . . . . . . . . . . . . . 4 63 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 64 6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 5 65 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 66 8. Normative References . . . . . . . . . . . . . . . . . . . . 5 67 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 69 1. Introduction 71 [RFC8445] describes a protocol, Interactive Connectivity 72 Establishment (ICE), for Network Address Translator (NAT) traversal 73 for UDP-based communication. 75 Typically, when using ICE, endpoints will exchange candidate 76 addresses, form a list of candidate pairs, and then test each 77 candidate pair to see if connectivity can be established. If the 78 test for a given pair fails, it is marked accordingly, and if all 79 pairs have failed, the overall ICE process is considered to have 80 failed. 82 During the process of connectivity checks, additional candidates may 83 be created as a result of successful inbound checks from the remote 84 peer. Such candidates are referred to as peer-reflexive candidates, 85 and once discovered, will be used to form new candidate pairs which 86 will be tested like any other. However, there is an inherent race 87 condition here; if, before learning about any peer-reflexive 88 candidates, an endpoint runs out of candidate pairs to check, either 89 because it has none, or it considers them all to have failed, it will 90 prematurely declare failure and terminate ICE processing. This race 91 condition can occur in many common situations. 93 This specification updates [RFC8445], by simply requiring that an 94 endpoint wait a minimum amount of time before declaring ICE failure, 95 even if there are no candidate pairs to check, or if all candidate 96 pairs have failed. This delay provides enough time for the discovery 97 of peer-reflexive candidates, which may eventually lead to ICE 98 processing completing successfully. 100 2. Conventions 102 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 103 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 104 "OPTIONAL" in this document are to be interpreted as described in BCP 105 14 [RFC2119] [RFC8174] when, and only when, they appear in all 106 capitals, as shown here. 108 3. Relevant Scenarios 110 As noted above, the core problem this specification attempts to 111 address is the situation where even after local gathering and remote 112 candidate signaling has completed, the ICE agent immediately ends up 113 with no valid pairs and no candidate pairs left to check, resulting 114 in a premature ICE failure. This failure is premature because not 115 enough time has elapsed to allow for discovery of peer-reflexive 116 candidates from inbound connectivity checks; if discovered, these 117 candidates are very likely to result in a valid pair. 119 In most ICE scenarios, the lengthy timeouts for connectivity checks, 120 typically tens of seconds, will prevent this problem for occuring. 121 However, there are certain specific cases where this problem will 122 frequently occur. 124 3.1. No Candidates From Peer 126 It is entirely legal for an ICE gent to provide zero candidates of 127 its own. If the agent somehow knows that the remote endpoint is 128 directly reachable, gathering local candidates is unnecessary and 129 will only cause delays; the remote endpoint can discover the 130 appropriate local candidate via connectivity checks. 132 However, following the procedures from [RFC8445] strictly will result 133 in immediate ICE failure, since the checklist at the remote endpoint 134 will be empty. 136 3.2. All Candidates Discarded 138 Even if the ICE agent provides candidates, they may be discarded by 139 the remote endpoint if it does not know what to do with them. For 140 example, candidates may use an address family that the remote 141 endpoint does not support, (e.g., a host candidate with an IPv6 142 address in a NAT64 scenario), or may not be usable for some other 143 reason (e.g., a candidate that contains a FQDN that fails to 144 resolve). 146 In these scenarios, when the candidates are discarded, the checklist 147 at the remote endpoint will once again be empty, leading to immediate 148 ICE failure. 150 3.3. Immediate Candidate Pair Failure 152 Section 7.2.5.2 of [RFC8445] describes several situations in which a 153 candidate pair will be considered to have failed, well before the 154 connectivity check timeout. 156 As a result, even if the ICE agent provides usable candidates, the 157 pairs created by the remote endpoint may fail immediately when 158 checked, e.g., a check to a nonroutable address that receives an 159 immediate ICMP error. 161 In this situation, the checklist at the remote endpoint may contain 162 only failed pairs, resulting in immediate ICE failure. 164 4. Update to RFC 8445 166 In order to avoid the problem raised by this document, the ICE agent 167 needs to wait enough time to allow peer-reflexive candidates to be 168 discovered. Accordingly, when full ICE implementations begin their 169 ICE processing, as described in [RFC8445], Section 6.1, the ICE agent 170 MUST set a timer, and its duration SHOULD be equal to the ICE agent's 171 connectivity check timeout. 173 This timeout value is chosen to roughly coincide with the maximum 174 possible duration of ICE connectivity checks from the remote peer, 175 which, if successful, could create peer-reflexive candidates. 176 Because the ICE agent doesn't know the exact number of candidate 177 pairs and pacing interval in use by the remote side, this timeout 178 value is simply a guess, albeit an educated one. Regardless, for 179 this particular problem, the desired benefits will be realized as 180 long as the ICE agent waits some reasonable amount of time. 182 While the timer is running, if a checklist has no pairs left to 183 check, i.e., there are no pairs that are not in the failed state, the 184 ICE agent MUST not conclude that ICE processing has failed, and MUST 185 wait for the timer to elapse before doing so. 187 One consequence of this behavior is that in cases where ICE should 188 fail, e.g., where both sides provide candidates with unresolvable 189 FQDNs ICE will no longer fail immediately, and only fail when the 190 aforementioned timer expires. However, because most ICE scenarios 191 require an extended period of time to determine failure, the fact 192 that some specific scenarios no longer fail fast should have minimal 193 application impact, if any. 195 5. Security Considerations 197 The security considerations for ICE are defined in [RFC8445]. This 198 specification only recommends ICE endpoints to wait for a certain 199 time of period before they declare ICE failure, and does not 200 introduce new security considerations. 202 6. IANA considerations 204 This specification makes no requests to IANA. 206 7. Acknowledgements 208 8. Normative References 210 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 211 Requirement Levels", BCP 14, RFC 2119, 212 DOI 10.17487/RFC2119, March 1997, . 215 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 216 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 217 May 2017, . 219 [RFC8445] Keranen, A., Holmberg, C., and J. Rosenberg, "Interactive 220 Connectivity Establishment (ICE): A Protocol for Network 221 Address Translator (NAT) Traversal", RFC 8445, 222 DOI 10.17487/RFC8445, July 2018, . 225 Authors' Addresses 227 Christer Holmberg 228 Ericsson 229 Hirsalantie 11 230 Jorvas 02420 231 Finland 233 Email: christer.holmberg@ericsson.com 235 Justin Uberti 236 Google 237 747 6th St W 238 Kirkland 98033 239 USA 241 Email: justin@uberti.name