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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) ** Obsolete normative reference: RFC 3484 (Obsoleted by RFC 6724) ** Obsolete normative reference: RFC 5245 (Obsoleted by RFC 8445, RFC 8839) ** Obsolete normative reference: RFC 6555 (Obsoleted by RFC 8305) Summary: 3 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 MMUSIC P. Martinsen 3 Internet-Draft T. Reddy 4 Intended status: Standards Track P. Patil 5 Expires: December 24, 2015 Cisco 6 June 22, 2015 8 ICE Multihomed and IPv4/IPv6 Dual Stack Fairness 9 draft-ietf-mmusic-ice-dualstack-fairness-01 11 Abstract 13 This document provides guidelines on how to make Interactive 14 Connectivity Establishment (ICE) conclude faster in multihomed and 15 IPv4/IPv6 dual-stack scenarios where broken paths exist. The 16 provided guidelines are backwards compatible with the original ICE 17 specification. 19 Status of This Memo 21 This Internet-Draft is submitted in full conformance with the 22 provisions of BCP 78 and BCP 79. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF). Note that other groups may also distribute 26 working documents as Internet-Drafts. The list of current Internet- 27 Drafts is at http://datatracker.ietf.org/drafts/current/. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet-Drafts as reference 32 material or to cite them other than as "work in progress." 34 This Internet-Draft will expire on December 24, 2015. 36 Copyright Notice 38 Copyright (c) 2015 IETF Trust and the persons identified as the 39 document authors. All rights reserved. 41 This document is subject to BCP 78 and the IETF Trust's Legal 42 Provisions Relating to IETF Documents 43 (http://trustee.ietf.org/license-info) in effect on the date of 44 publication of this document. Please review these documents 45 carefully, as they describe your rights and restrictions with respect 46 to this document. Code Components extracted from this document must 47 include Simplified BSD License text as described in Section 4.e of 48 the Trust Legal Provisions and are provided without warranty as 49 described in the Simplified BSD License. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 54 2. Notational Conventions . . . . . . . . . . . . . . . . . . . 3 55 3. Improving ICE Multihomed Fairness . . . . . . . . . . . . . . 3 56 4. Improving ICE Dual Stack Fairness . . . . . . . . . . . . . . 4 57 5. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 4 58 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 59 7. Security Considerations . . . . . . . . . . . . . . . . . . . 7 60 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 61 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 62 9.1. Normative References . . . . . . . . . . . . . . . . . . 7 63 9.2. Informative References . . . . . . . . . . . . . . . . . 8 64 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 66 1. Introduction 68 Applications should take special care to deprioritize network 69 interfaces known to provide unreliable connectivity when operating in 70 a multihomed environment. For example certain tunnel services might 71 provide unreliable connectivity. Doing so will ensure a more fair 72 distribution of the connectivity checks across available network 73 interfaces on the device. The simple guidelines presented here 74 describes how to deprioritize interfaces known by the application to 75 provide unreliable connectivity. 77 There is a also a need to introduce more fairness when handling of 78 connectivity checks for different IP address families in dual-stack 79 IPv4/IPv6 ICE scenarios. Section 4.1.2.1 of ICE [RFC5245] points to 80 [RFC3484] for prioritizing among the different IP families. 81 [RFC3484] is obsoleted by [RFC6724] but following the recommendations 82 from the updated RFC will lead to prioritization of IPv6 over IPv4 83 for the same candidate type. Due to this, connectivity checks for 84 candidates of the same type (host, reflexive or relay) are sent such 85 that an IP address family is completely depleted before checks from 86 the other address family are started. This results in user 87 noticeable setup delays if the path for the prioritized address 88 family is broken. 90 To avoid such user noticeable delays when either IPv6 or IPv4 path is 91 broken or excessive slow, this specification encourages intermingling 92 the different address families when connectivity checks are 93 performed. Introducing IP address family fairness into ICE 94 connectivity checks will lead to more sustained dual-stack IPv4/IPv6 95 deployment as users will no longer have an incentive to disable IPv6. 97 The cost is a small penalty to the address type that otherwise would 98 have been prioritized. 100 This document describes how to fairly order the candidates in 101 multihomed and dual-stack environments, thus affecting the sending 102 order of the connectivity checks. Ultimately it is up to the agent 103 to decide what candidate pair is best suited for transporting media. 105 The guidelines outlined in this specification are backward compatible 106 with a standard ICE implementation. This specification only alters 107 the values used to create the resulting checklists in such a way that 108 the core mechanisms from ICE [RFC5245] are still in effect. The 109 introduced fairness might be better, but not worse than what exists 110 today. 112 2. Notational Conventions 114 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 115 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 116 document are to be interpreted as described in [RFC2119]. 118 This document uses terminology defined in [RFC5245]. 120 3. Improving ICE Multihomed Fairness 122 A multihomed ICE agent can potentially send and receive connectivity 123 checks on all available interfaces and IP addresses. It is possible 124 for an interface to have several IP addresses associated with it. To 125 avoid unnecessary delay when performing connectivity checks it would 126 be beneficial to prioritize interfaces and IP addresses known by the 127 agent to provide stable connectivity. If the agent have access to 128 information about the physical network it is connected to (Like SSID 129 in a WiFi Network) this can be used as information regarding how that 130 network interface should be prioritized at this point in time. 132 The application knowledge regarding the reliability of an interface 133 can also be based on simple metrics like previous connection success/ 134 failure rates or a more static model based on interface types like 135 wired, wireless, cellular, virtual, tunneled and so on. 137 Candidates from a interface known to the application to provide 138 unreliable connectivity SHOULD get a low candidate priority. This 139 ensures they appear near the end of the candidate list, and would be 140 the last to be tested during the connectivity check phase. This 141 allows candidate pairs more likely to succeed to be tested first. 143 If the application is unable to get any interface information 144 regarding type or unable to store any relevant metrics, it SHOULD 145 treat all interfaces as if they have reliable connectivity. This 146 ensures all interfaces gets their fair chance to perform their 147 connectivity checks. 149 4. Improving ICE Dual Stack Fairness 151 Candidates SHOULD be prioritized such that a long sequence of 152 candidates belonging to the same address family will be intermingled 153 with candidates from an alternate IP family. For example, promoting 154 IPv4 candidates in the presence of many IPv6 candidates such that an 155 IPv4 address candidate is always present after a small sequence of 156 IPv6 candidates, i.e., reordering candidates such that both IPv6 and 157 IPv4 candidates get a fair chance during the connectivity check 158 phase. This makes ICE connectivity checks more responsive to broken 159 path failures of an address family. 161 An ICE agent can choose an algorithm or a technique of its choice to 162 ensure that the resulting check lists have a fair intermingled mix of 163 IPv4 and IPv6 address families. However, modifying the check list 164 directly can lead to uncoordinated local and remote check lists that 165 result in ICE taking longer to complete or in the worst case scenario 166 fail. The best approach is to modify the formula for calculating the 167 candidate priority value described in ICE [RFC5245] section 4.1.2.1. 169 Implementations SHOULD prioritize IPv6 candidates by putting some of 170 them first in the the intermingled checklist. This increases the 171 chance of a IPv6 connectivity checks to complete first and be ready 172 for nomination or usage. This enables implementations to follow the 173 intent of [RFC6555] "Happy Eyeballs: Success with Dual-Stack Hosts". 174 It is worth noting that the timing recommendations in [RFC6555] are 175 to excessive for ICE usage. 177 5. Compatibility 179 ICE [RFC5245] section 4.1.2 states that the formula in section 180 4.1.2.1 SHOULD be used to calculate the candidate priority. The 181 formula is as follows: 183 priority = (2^24)*(type preference) + 184 (2^8)*(local preference) + 185 (2^0)*(256 - component ID) 187 ICE [RFC5245] section 4.1.2.2 has guidelines for how the type 188 preference and local preference value should be chosen. Instead of 189 having a static local preference value for IPv4 and IPv6 addresses, 190 it is possible to choose this value dynamically in such a way that 191 IPv4 and IPv6 address candidate priorities ends up intermingled 192 within the same candidate type. It is also possible to assign lower 193 priorities to IP addresses derived from unreliable interfaces using 194 the local preference value. 196 It is worth mentioning that [RFC5245] section 4.1.2 say that; "if 197 there are multiple candidates for a particular component for a 198 particular media stream that have the same type, the local preference 199 MUST be unique for each one". 201 The local type preference can be dynamically changed in such a way 202 that IPv4 and IPv6 address candidates end up intermingled regardless 203 of candidate type. This is useful if there are a lot of IPv6 host 204 candidates effectively blocking connectivity checks for IPv4 server 205 reflexive candidates. 207 Candidates with IP addresses from a unreliable interface SHOULD be 208 ordered at the end of the checklist. Not intermingled as the dual- 209 stack candidates. 211 The list below shows a sorted local candidate list where the priority 212 is calculated in such a way that the IPv4 and IPv6 candidates are 213 intermingled (No multihomed candidates). To allow for earlier 214 connectivity checks for the IPv4 server reflexive candidates, some of 215 the IPv6 host candidates are demoted. This is just an example of how 216 a candidate priorities can be calculated to provide better fairness 217 between IPv4 and IPv6 candidates without breaking any of the ICE 218 connectivity checks. 220 Candidate Address Component 221 Type Type ID Priority 222 ------------------------------------------- 223 (1) HOST IPv6 (1) 2129289471 224 (2) HOST IPv6 (2) 2129289470 225 (3) HOST IPv4 (1) 2129033471 226 (4) HOST IPv4 (2) 2129033470 227 (5) HOST IPv6 (1) 2128777471 228 (6) HOST IPv6 (2) 2128777470 229 (7) HOST IPv4 (1) 2128521471 230 (8) HOST IPv4 (2) 2128521470 231 (9) HOST IPv6 (1) 2127753471 232 (10) HOST IPv6 (2) 2127753470 233 (11) SRFLX IPv6 (1) 1693081855 234 (12) SRFLX IPv6 (2) 1693081854 235 (13) SRFLX IPv4 (1) 1692825855 236 (14) SRFLX IPv4 (2) 1692825854 237 (15) HOST IPv6 (1) 1692057855 238 (16) HOST IPv6 (2) 1692057854 239 (17) RELAY IPv6 (1) 15360255 240 (18) RELAY IPv6 (2) 15360254 241 (19) RELAY IPv4 (1) 15104255 242 (20) RELAY IPv4 (2) 15104254 244 SRFLX = server reflexive 246 Note that the list does not alter the component ID part of the 247 formula. This keeps the different components (RTP and RTCP) close in 248 the list. What matters is the ordering of the candidates with 249 component ID 1. Once the checklist is formed for a media stream the 250 candidate pair with component ID 1 will be tested first. If ICE 251 connectivity check is successful then other candidate pairs with the 252 same foundation will be unfrozen ([RFC5245] section 5.7.4. Computing 253 States). 255 The local and remote agent can have different algorithms for choosing 256 the local preference and type preference values without impacting the 257 synchronization between the local and remote check lists. 259 The check list is made up by candidate pairs. A candidate pair is 260 two candidates paired up and given a candidate pair priority as 261 described in [RFC5245] section 5.7.2. Using the pair priority 262 formula: 264 pair priority = 2^32*MIN(G,D) + 2*MAX(G,D) + (G>D?1:0) 266 Where G is the candidate priority provided by the controlling agent 267 and D the candidate priority provided by the controlled agent. This 268 ensures that the local and remote check lists are coordinated. 270 Even if the two agents have different algorithms for choosing the 271 candidate priority value to get an intermingled set of IPv4 and IPv6 272 candidates, the resulting checklist, that is a list sorted by the 273 pair priority value, will be identical on the two agents. 275 The agent that has promoted IPv4 cautiously i.e. lower IPv4 candidate 276 priority values compared to the other agent, will influence the check 277 list the most due to (2^32*MIN(G,D)) in the formula. 279 These recommendations are backward compatible with a standard ICE 280 implementation. The resulting local and remote checklist will still 281 be synchronized. The introduced fairness might be better, but not 282 worse than what exists today 284 A test implementation with an example algorithm is available 285 [ICE_dualstack_imp]. 287 6. IANA Considerations 289 None. 291 7. Security Considerations 293 STUN connectivity check using MAC computed during key exchanged in 294 the signaling channel provides message integrity and data origin 295 authentication as described in section 2.5 of [RFC5245] apply to this 296 use. 298 8. Acknowledgements 300 Authors would like to thank Dan Wing, Ari Keranen, Bernard Aboba, 301 Martin Thomson, Jonathan Lennox, Balint Menyhart, Ole Troan and Simon 302 Perreault for their comments and review. 304 9. References 306 9.1. Normative References 308 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 309 Requirement Levels", BCP 14, RFC 2119, March 1997. 311 [RFC3484] Draves, R., "Default Address Selection for Internet 312 Protocol version 6 (IPv6)", RFC 3484, February 2003. 314 [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment 315 (ICE): A Protocol for Network Address Translator (NAT) 316 Traversal for Offer/Answer Protocols", RFC 5245, April 317 2010. 319 [RFC6555] Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with 320 Dual-Stack Hosts", RFC 6555, April 2012. 322 [RFC6724] Thaler, D., Draves, R., Matsumoto, A., and T. Chown, 323 "Default Address Selection for Internet Protocol Version 6 324 (IPv6)", RFC 6724, September 2012. 326 9.2. Informative References 328 [ICE_dualstack_imp] 329 Martinsen, P., "ICE DualStack Test Implementation github 330 repo", . 333 Authors' Addresses 335 Paal-Erik Martinsen 336 Cisco Systems, Inc. 337 Philip Pedersens Vei 22 338 Lysaker, Akershus 1325 339 Norway 341 Email: palmarti@cisco.com 343 Tirumaleswar Reddy 344 Cisco Systems, Inc. 345 Cessna Business Park, Varthur Hobli 346 Sarjapur Marathalli Outer Ring Road 347 Bangalore, Karnataka 560103 348 India 350 Email: tireddy@cisco.com 352 Prashanth Patil 353 Cisco Systems, Inc. 354 Bangalore 355 India 357 Email: praspati@cisco.com