idnits 2.17.1 draft-ietf-tsvwg-sctp-prpolicies-04.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 : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (September 28, 2014) is 3470 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references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 4960 (Obsoleted by RFC 9260) == Outdated reference: A later version (-13) exists of draft-ietf-rtcweb-data-channel-11 Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group M. Tuexen 3 Internet-Draft Muenster Univ. of Appl. Sciences 4 Intended status: Standards Track R. Seggelmann 5 Expires: April 1, 2015 T-Systems International GmbH 6 R. Stewart 7 Netflix, Inc. 8 S. Loreto 9 Ericsson 10 September 28, 2014 12 Additional Policies for the Partial Reliability Extension of the Stream 13 Control Transmission Protocol 14 draft-ietf-tsvwg-sctp-prpolicies-04.txt 16 Abstract 18 This document defines two additional policies for the Partial 19 Reliability Extension of the Stream Control Transmission Protocol 20 (PR-SCTP) allowing to limit the number of retransmissions or to 21 prioritize user messages for more efficient send buffer usage. 23 Status of This Memo 25 This Internet-Draft is submitted in full conformance with the 26 provisions of BCP 78 and BCP 79. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF). Note that other groups may also distribute 30 working documents as Internet-Drafts. The list of current Internet- 31 Drafts is at http://datatracker.ietf.org/drafts/current/. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 This Internet-Draft will expire on April 1, 2015. 40 Copyright Notice 42 Copyright (c) 2014 IETF Trust and the persons identified as the 43 document authors. All rights reserved. 45 This document is subject to BCP 78 and the IETF Trust's Legal 46 Provisions Relating to IETF Documents 47 (http://trustee.ietf.org/license-info) in effect on the date of 48 publication of this document. Please review these documents 49 carefully, as they describe your rights and restrictions with respect 50 to this document. Code Components extracted from this document must 51 include Simplified BSD License text as described in Section 4.e of 52 the Trust Legal Provisions and are provided without warranty as 53 described in the Simplified BSD License. 55 Table of Contents 57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 58 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3 59 3. Additional PR-SCTP Policies . . . . . . . . . . . . . . . . . 3 60 3.1. Limited Retransmissions Policy . . . . . . . . . . . . . 3 61 3.2. Priority Policy . . . . . . . . . . . . . . . . . . . . . 3 62 4. Socket API Considerations . . . . . . . . . . . . . . . . . . 4 63 4.1. Data Types . . . . . . . . . . . . . . . . . . . . . . . 4 64 4.2. Support for Added PR-SCTP Policies . . . . . . . . . . . 4 65 4.3. Socket Option for Getting the Stream Specific PR-SCTP 66 Status (SCTP_PR_STREAM_STATUS) . . . . . 5 67 4.4. Socket Option for Getting the Association Specific PR- 68 SCTP Status (SCTP_PR_ASSOC_STATUS) . . . 6 69 4.5. Socket Option for Getting and Setting the PR-SCTP Support 70 (SCTP_PR_SUPPORTED) . . . . . . . . . . . . . . . . . . . 7 71 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 72 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 73 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8 74 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 75 8.1. Normative References . . . . . . . . . . . . . . . . . . 8 76 8.2. Informative References . . . . . . . . . . . . . . . . . 8 77 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 79 1. Introduction 81 The SCTP Partial Reliability Extension (PR-SCTP) defined in [RFC3758] 82 provides a generic method for senders to abandon user messages. The 83 decision to abandon a user message is sender side only and the exact 84 condition is called a PR-SCTP policy. [RFC3758] also defines one 85 particular PR-SCTP policy, called Timed Reliability. This allows the 86 sender to specify a timeout for a user message after which the SCTP 87 stack abandons the user message. 89 This document specifies the following two additional PR-SCTP 90 policies: 92 Limited Retransmission Policy: Allows to limit the number of 93 retransmissions. 95 Priority Policy: Allows to discard lower priority messages if space 96 for higher priority messages is needed in the send buffer. 98 2. Conventions 100 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 101 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 102 document are to be interpreted as described in [RFC2119]. 104 3. Additional PR-SCTP Policies 106 This section defines two new PR-SCTP policies, one in each 107 subsection. 109 Please note that it is REQUIRED to implement [RFC3758], if you want 110 to implement these additional policies. However, these additional 111 policies are OPTIONAL when implementing [RFC3758]. 113 3.1. Limited Retransmissions Policy 115 Using the Limited Retransmission Policy allows the sender of a user 116 message to specify an upper limit for the number of retransmissions 117 for each DATA chunk of the given user messages. The sender MUST 118 abandon a user message if the number of retransmissions of any of the 119 DATA chunks of the user message would exceed the provided limit. The 120 sender MUST perform all other actions required for processing the 121 retransmission event, like possibly adopting the congestion window 122 and the retransmission timeout. Please note that the number of 123 retransmissions includes both fast and timer based retransmissions. 125 The sender MAY limit the number of retransmissions to 0. This will 126 result in abandoning the message when it would get retransmitted for 127 the first time. The use of this setting provides a service similar 128 to UDP, which also does not perform any retransmissions. 130 The Limited Retransmissions Policy is used for data channels in the 131 WebRTC protocol stack. See [I-D.ietf-rtcweb-data-channel] for more 132 information. 134 3.2. Priority Policy 136 Using the Priority Policy allows the sender of a user message to 137 specify a priority. When storing a user message in the send buffer 138 while there is not enough available space, the SCTP stack at the 139 sender side MAY abandon other user messages of the same SCTP 140 association with a priority lower than the provided one. The 141 algorithm for selecting the message being abandoned is implementation 142 specific. 144 After lower priority messages have been abandoned high priority 145 messages can be transferred without blocking the send call (if used 146 in blocking mode) or the send call fails (if used in non-blocking 147 mode). 149 The Priority Policy can be used in the IPFIX protocol stack. See 150 [RFC7011] for more information. 152 4. Socket API Considerations 154 This section describes how the socket API defined in [RFC6458] is 155 extended to support the newly defined PR-SCTP policies, to provide 156 some statistical information and to control the negotiation of the 157 PR-SCTP extension during the SCTP association setup. 159 Please note that this section is informational only. 161 4.1. Data Types 163 This section uses data types from [IEEE.1003-1G.1997]: uintN_t means 164 an unsigned integer of exactly N bits (e.g. uint16_t). This is the 165 same as in [RFC6458]. 167 4.2. Support for Added PR-SCTP Policies 169 As defined in [RFC6458], the PR-SCTP policy is specified and 170 configured by using the following sctp_prinfo structure: 172 struct sctp_prinfo { 173 uint16_t pr_policy; 174 uint32_t pr_value; 175 }; 177 When the Limited Retransmission Policy described in Section 3.1 is 178 used, pr_policy has the value SCTP_PR_SCTP_RTX and the number of 179 retransmissions is given in pr_value. 181 For using the Priority Policy described in Section 3.2, pr_policy has 182 the value SCTP_PR_SCTP_PRIO. The priority is given in pr_value. The 183 value of zero is the highest priority and larger numbers in pr_value 184 denote lower priorities. 186 The following table summarizes the possible parameter settings 187 defined in [RFC6458] and this document: 189 +-------------------+---------------------------+---------------+ 190 | pr_policy | pr_value | Specification | 191 +-------------------+---------------------------+---------------+ 192 | SCTP_PR_SCTP_NONE | Ignored | [RFC6458] | 193 | SCTP_PR_SCTP_TTL | Lifetime in ms | [RFC6458] | 194 | SCTP_PR_SCTP_RTX | Number of retransmissions | Section 3.1 | 195 | SCTP_PR_SCTP_PRIO | Priority | Section 3.2 | 196 +-------------------+---------------------------+---------------+ 198 4.3. Socket Option for Getting the Stream Specific PR-SCTP Status 199 (SCTP_PR_STREAM_STATUS) 201 This socket option uses IPPROTO_SCTP as its level and 202 SCTP_PR_STREAM_STATUS as its name. It can only be used with 203 getsockopt(), but not with setsockopt(). The socket option value 204 uses the following structure: 206 struct sctp_prstatus { 207 sctp_assoc_t sprstat_assoc_id; 208 uint16_t sprstat_sid; 209 uint16_t sprstat_policy; 210 uint64_t sprstat_abandoned_unsent; 211 uint64_t sprstat_abandoned_sent; 212 }; 214 sprstat_assoc_id: This parameter is ignored for one-to-one style 215 sockets. For one-to-many style sockets this parameter indicates 216 for which association the user wants the information. It is an 217 error to use SCTP_{CURRENT|ALL|FUTURE}_ASSOC in sprstat_assoc_id. 219 sprstat_sid: This parameter indicates for which outgoing SCTP stream 220 the user wants the information. 222 sprstat_policy: This parameter indicates for which PR-SCTP policy 223 the user wants the information. It is an error to use 224 SCTP_PR_SCTP_NONE in sprstat_policy. If SCTP_PR_SCTP_ALL is used, 225 the counters provided are aggregated over all supported policies. 227 sprstat_abandoned_unsent: The number of user messages which have 228 been abandoned using the policy specified in sprstat_policy on the 229 stream specified in sprstat_sid for the association specified by 230 sprstat_assoc_id, before any part of the user message could be 231 sent. 233 sprstat_abandoned_sent: The number of user messages which have been 234 abandoned using the policy specified in sprstat_policy on the 235 stream specified in sprstat_sid for the association specified by 236 sprstat_assoc_id, after a part of the user message has been sent. 238 There are separate counters for unsent and sent user messages because 239 the SCTP_SEND_FAILED_EVENT supports a similar differentiation. 240 Please note that an abandoned large user message requiring an SCTP 241 level fragmentation is reported in the sprstat_abandoned_sent counter 242 as soon as at least one fragment of it has been sent. Therefore each 243 abandoned user message is either counted in sprstat_abandoned_unsent 244 or sprstat_abandoned_sent. 246 If more detailed information about abandoned user messages is 247 required, the subscription to the SCTP_SEND_FAILED_EVENT is 248 recommended. Please note that some implementations might not support 249 this option on purpose, since it increases the resources needed for 250 an outgoing SCTP stream. For the same reasons, some implementations 251 might only support using SCTP_PR_SCTP_ALL in sprstat_policy. 253 sctp_opt_info() needs to be extended to support 254 SCTP_PR_STREAM_STATUS. 256 4.4. Socket Option for Getting the Association Specific PR-SCTP Status 257 (SCTP_PR_ASSOC_STATUS) 259 This socket option uses IPPROTO_SCTP as its level and 260 SCTP_PR_ASSOC_STATUS as its name. It can only be used with 261 getsockopt(), but not with setsockopt(). The socket option value 262 uses the same structure as described in Section 4.3: 264 struct sctp_prstatus { 265 sctp_assoc_t sprstat_assoc_id; 266 uint16_t sprstat_sid; 267 uint16_t sprstat_policy; 268 uint64_t sprstat_abandoned_unsent; 269 uint64_t sprstat_abandoned_sent; 270 }; 272 sprstat_assoc_id: This parameter is ignored for one-to-one style 273 sockets. For one-to-many style sockets this parameter indicates 274 for which association the user wants the information. It is an 275 error to use SCTP_{CURRENT|ALL|FUTURE}_ASSOC in sprstat_assoc_id. 277 sprstat_sid: This parameter is ignored. 279 sprstat_policy: This parameter indicates for which PR-SCTP policy 280 the user wants the information. It is an error to use 281 SCTP_PR_SCTP_NONE in sprstat_policy. If SCTP_PR_SCTP_ALL is used, 282 the counters provided are aggregated over all supported policies. 284 sprstat_abandoned_unsent: The number of user messages which have 285 been abandoned using the policy specified in sprstat_policy for 286 the association specified by sprstat_assoc_id, before any part of 287 the user message could be sent. 289 sprstat_abandoned_sent: The number of user messages which have been 290 abandoned using the policy specified in sprstat_policy for the 291 association specified by sprstat_assoc_id, after a part of the 292 user message has been sent. 294 There are separate counters for unsent and sent user messages because 295 the SCTP_SEND_FAILED_EVENT supports a similar differentiation. 296 Please note that an abandoned large user message requiring an SCTP 297 level fragmentation is reported in the sprstat_abandoned_sent counter 298 as soon as at least one fragment of it has been sent. Therefore each 299 abandoned user message is either counted in sprstat_abandoned_unsent 300 or sprstat_abandoned_sent. 302 If more detailed information about abandoned user messages is 303 required, the usage of the option described in Section 4.3 or the 304 subscription to the SCTP_SEND_FAILED_EVENT is recommended. 306 sctp_opt_info() needs to be extended to support SCTP_PR_ASSOC_STATUS. 308 4.5. Socket Option for Getting and Setting the PR-SCTP Support 309 (SCTP_PR_SUPPORTED) 311 This socket option allows the enabling or disabling of the 312 negotiation of PR-SCTP support for future associations. For existing 313 associations it allows to query whether PR-SCTP support was 314 negotiated or not on a particular association. 316 Whether PR-SCTP is enabled or not per default is implementation 317 specific. 319 This socket option uses IPPROTO_SCTP as its level and 320 SCTP_PR_SUPPORTED as its name. It can be used with getsockopt() and 321 setsockopt(). The socket option value uses the following structure 322 defined in [RFC6458]: 324 struct sctp_assoc_value { 325 sctp_assoc_t assoc_id; 326 uint32_t assoc_value; 327 }; 329 assoc_id: This parameter is ignored for one-to-one style sockets. 330 For one-to-many style sockets, this parameter indicates upon which 331 association the user is performing an action. The special 332 sctp_assoc_t SCTP_FUTURE_ASSOC can also be used, it is an error to 333 use SCTP_{CURRENT|ALL}_ASSOC in assoc_id. 335 assoc_value: A non-zero value encodes the enabling of PR-SCTP 336 whereas a value of 0 encodes the disabling of PR-SCTP. 338 sctp_opt_info() needs to be extended to support SCTP_PR_SUPPORTED. 340 5. IANA Considerations 342 This document requires no actions from IANA. 344 6. Security Considerations 346 This document does not add any additional security considerations in 347 addition to the ones given in [RFC4960], [RFC3758], and [RFC6458]. 348 As indicated in the Security Section of [RFC3758], transport layer 349 security in the form of TLS over SCTP (see [RFC3436]) can't be used 350 for PR-SCTP. However, DTLS over SCTP (see [RFC6083]) could be used 351 instead. It should also be noted that using PR-SCTP for an SCTP 352 association doesn't allow that association to behave more 353 aggressively congestion-control wise than an SCTP association not 354 using PR-SCTP. 356 7. Acknowledgments 358 The authors wish to thank Gorry Fairhurst, Karen Egede Nielsen, Ka- 359 Cheong Poon, Irene Ruengeler, Jamal Hadi Salim, and Vlad Yasevich for 360 their invaluable comments. 362 8. References 364 8.1. Normative References 366 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 367 Requirement Levels", BCP 14, RFC 2119, March 1997. 369 [RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P. 370 Conrad, "Stream Control Transmission Protocol (SCTP) 371 Partial Reliability Extension", RFC 3758, May 2004. 373 [RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC 374 4960, September 2007. 376 8.2. Informative References 378 [RFC3436] Jungmaier, A., Rescorla, E., and M. Tuexen, "Transport 379 Layer Security over Stream Control Transmission Protocol", 380 RFC 3436, December 2002. 382 [RFC6083] Tuexen, M., Seggelmann, R., and E. Rescorla, "Datagram 383 Transport Layer Security (DTLS) for Stream Control 384 Transmission Protocol (SCTP)", RFC 6083, January 2011. 386 [RFC6458] Stewart, R., Tuexen, M., Poon, K., Lei, P., and V. 387 Yasevich, "Sockets API Extensions for the Stream Control 388 Transmission Protocol (SCTP)", RFC 6458, December 2011. 390 [RFC7011] Claise, B., Trammell, B., and P. Aitken, "Specification of 391 the IP Flow Information Export (IPFIX) Protocol for the 392 Exchange of Flow Information", STD 77, RFC 7011, September 393 2013. 395 [I-D.ietf-rtcweb-data-channel] 396 Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data 397 Channels", draft-ietf-rtcweb-data-channel-11 (work in 398 progress), July 2014. 400 [IEEE.1003-1G.1997] 401 Institute of Electrical and Electronics Engineers, 402 "Protocol Independent Interfaces", IEEE Standard 1003.1G, 403 March 1997. 405 Authors' Addresses 407 Michael Tuexen 408 Muenster University of Applied Sciences 409 Stegerwaldstrasse 39 410 48565 Steinfurt 411 DE 413 Email: tuexen@fh-muenster.de 415 Robin Seggelmann 416 T-Systems International GmbH 417 Fasanenweg 5 418 70771 Leinfelden-Echterdingen 419 DE 421 Email: robin.seggelmann@t-systems.com 422 Randall R. Stewart 423 Netflix, Inc. 424 Chapin, SC 29036 425 US 427 Email: randall@lakerest.net 429 Salvatore Loreto 430 Ericsson 431 Hirsalantie 11 432 Jorvas 02420 433 FI 435 Email: Salvatore.Loreto@ericsson.com