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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) Summary: 1 error (**), 0 flaws (~~), 1 warning (==), 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: August 11, 2015 T-Systems International GmbH 6 R. Stewart 7 Netflix, Inc. 8 S. Loreto 9 Ericsson 10 February 7, 2015 12 Additional Policies for the Partial Reliability Extension of the Stream 13 Control Transmission Protocol 14 draft-ietf-tsvwg-sctp-prpolicies-07.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 August 11, 2015. 40 Copyright Notice 42 Copyright (c) 2015 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 . . . . . . . . . . . . . . . . . 9 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] refers to them as 85 'PR-SCTP Services'). [RFC3758] also defines one particular PR-SCTP 86 policy, called Timed Reliability. This allows the sender to specify 87 a timeout for a user message after which the SCTP stack abandons the 88 user message. 90 This document specifies the following two additional PR-SCTP 91 policies: 93 Limited Retransmission Policy: Allows to limit the number of 94 retransmissions. 96 Priority Policy: Allows to discard lower priority messages if space 97 for higher priority messages is needed in the send buffer. 99 2. Conventions 101 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 102 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 103 document are to be interpreted as described in [RFC2119]. 105 3. Additional PR-SCTP Policies 107 This section defines two new PR-SCTP policies, one in each 108 subsection. 110 Please note that it is REQUIRED to implement [RFC3758], if you want 111 to implement these additional policies. However, these additional 112 policies are OPTIONAL when implementing [RFC3758]. 114 3.1. Limited Retransmissions Policy 116 Using the Limited Retransmission Policy allows the sender of a user 117 message to specify an upper limit for the number of retransmissions 118 for each DATA chunk of the given user messages. The sender MUST 119 abandon a user message if the number of retransmissions of any of the 120 DATA chunks of the user message would exceed the provided limit. The 121 sender MUST perform all other actions required for processing the 122 retransmission event, such as adapting the congestion window and the 123 retransmission timeout. Please note that the number of 124 retransmissions includes both fast and timer-based retransmissions. 126 The sender MAY limit the number of retransmissions to 0. This will 127 result in abandoning the message when it would get retransmitted for 128 the first time. The use of this setting provides a service similar 129 to UDP, which also does not perform any retransmissions. 131 Please note that using this policy does not affect the handling of 132 the thresholds 'Association.Max.Retrans' and 'Path.Max.Retrans' as 133 specified in Section 8 of [RFC4960]. 135 The WebRTC protocol stack (see [I-D.ietf-rtcweb-data-channel]), is an 136 example of where the Limited Retransmissions Policy is used. 138 3.2. Priority Policy 140 Using the Priority Policy allows the sender of a user message to 141 specify a priority. When storing a user message in the send buffer 142 while there is not enough available space, the SCTP stack at the 143 sender side MAY abandon other user message(s) of the same SCTP 144 association (with the same or a different stream) with a priority 145 lower than the provided one. User messages sent reliable are 146 considered having a priority higher than all messages sent with the 147 Priority Policy. The algorithm for selecting the message(s) being 148 abandoned is implementation specific. 150 After lower priority messages have been abandoned high priority 151 messages can be transferred without the send call blocking (if used 152 in blocking mode) or the send call failing (if used in non-blocking 153 mode). 155 The IPFIX protocol stack (see [RFC7011]) is an example of where the 156 Priority Policy can be used. Template records would be sent with 157 full reliability, while billing, security-related, and other 158 monitoring flow records would be sent using the Priority Policy with 159 varying priority. The priority of security related flow-records 160 would be chosen higher than the the priority of monitoring flow 161 records. 163 4. Socket API Considerations 165 This section describes how the socket API defined in [RFC6458] is 166 extended to support the newly defined PR-SCTP policies, to provide 167 some statistical information and to control the negotiation of the 168 PR-SCTP extension during the SCTP association setup. 170 Please note that this section is informational only. 172 4.1. Data Types 174 This section uses data types from [IEEE.1003-1G.1997]: uintN_t means 175 an unsigned integer of exactly N bits (e.g. uint16_t). This is the 176 same as in [RFC6458]. 178 4.2. Support for Added PR-SCTP Policies 180 As defined in [RFC6458], the PR-SCTP policy is specified and 181 configured by using the following sctp_prinfo structure: 183 struct sctp_prinfo { 184 uint16_t pr_policy; 185 uint32_t pr_value; 186 }; 188 When the Limited Retransmission Policy described in Section 3.1 is 189 used, pr_policy has the value SCTP_PR_SCTP_RTX and the number of 190 retransmissions is given in pr_value. 192 When using the Priority Policy described in Section 3.2, pr_policy 193 has the value SCTP_PR_SCTP_PRIO. The priority is given in pr_value. 194 The value of zero is the highest priority and larger numbers in 195 pr_value denote lower priorities. 197 The following table summarizes the possible parameter settings 198 defined in [RFC6458] and this document: 200 +-------------------+---------------------------+---------------+ 201 | pr_policy | pr_value | Specification | 202 +-------------------+---------------------------+---------------+ 203 | SCTP_PR_SCTP_NONE | Ignored | [RFC6458] | 204 | SCTP_PR_SCTP_TTL | Lifetime in ms | [RFC6458] | 205 | SCTP_PR_SCTP_RTX | Number of retransmissions | Section 3.1 | 206 | SCTP_PR_SCTP_PRIO | Priority | Section 3.2 | 207 +-------------------+---------------------------+---------------+ 209 4.3. Socket Option for Getting the Stream Specific PR-SCTP Status 210 (SCTP_PR_STREAM_STATUS) 212 This socket option uses IPPROTO_SCTP as its level and 213 SCTP_PR_STREAM_STATUS as its name. It can only be used with 214 getsockopt(), but not with setsockopt(). The socket option value 215 uses the following structure: 217 struct sctp_prstatus { 218 sctp_assoc_t sprstat_assoc_id; 219 uint16_t sprstat_sid; 220 uint16_t sprstat_policy; 221 uint64_t sprstat_abandoned_unsent; 222 uint64_t sprstat_abandoned_sent; 223 }; 225 sprstat_assoc_id: This parameter is ignored for one-to-one style 226 sockets. For one-to-many style sockets this parameter indicates 227 for which association the user wants the information. It is an 228 error to use SCTP_{CURRENT|ALL|FUTURE}_ASSOC in sprstat_assoc_id. 230 sprstat_sid: This parameter indicates for which outgoing SCTP stream 231 the user wants the information. 233 sprstat_policy: This parameter indicates for which PR-SCTP policy 234 the user wants the information. It is an error to use 235 SCTP_PR_SCTP_NONE in sprstat_policy. If SCTP_PR_SCTP_ALL is used, 236 the counters provided are aggregated over all supported policies. 238 sprstat_abandoned_unsent: The number of user messages which have 239 been abandoned using the policy specified in sprstat_policy on the 240 stream specified in sprstat_sid for the association specified by 241 sprstat_assoc_id, before any part of the user message could be 242 sent. 244 sprstat_abandoned_sent: The number of user messages which have been 245 abandoned using the policy specified in sprstat_policy on the 246 stream specified in sprstat_sid for the association specified by 247 sprstat_assoc_id, after a part of the user message has been sent. 249 There are separate counters for unsent and sent user messages because 250 the SCTP_SEND_FAILED_EVENT supports a similar differentiation. 251 Please note that an abandoned large user message requiring an SCTP 252 level fragmentation is reported in the sprstat_abandoned_sent counter 253 as soon as at least one fragment of it has been sent. Therefore each 254 abandoned user message is either counted in sprstat_abandoned_unsent 255 or sprstat_abandoned_sent. 257 If more detailed information about abandoned user messages is 258 required, the subscription to the SCTP_SEND_FAILED_EVENT is 259 recommended. Please note that some implementations might choose not 260 to support this option, since it increases the resources needed for 261 an outgoing SCTP stream. For the same reasons, some implementations 262 might only support using SCTP_PR_SCTP_ALL in sprstat_policy. 264 sctp_opt_info() needs to be extended to support 265 SCTP_PR_STREAM_STATUS. 267 4.4. Socket Option for Getting the Association Specific PR-SCTP Status 268 (SCTP_PR_ASSOC_STATUS) 270 This socket option uses IPPROTO_SCTP as its level and 271 SCTP_PR_ASSOC_STATUS as its name. It can only be used with 272 getsockopt(), but not with setsockopt(). The socket option value 273 uses the same structure as described in Section 4.3: 275 struct sctp_prstatus { 276 sctp_assoc_t sprstat_assoc_id; 277 uint16_t sprstat_sid; 278 uint16_t sprstat_policy; 279 uint64_t sprstat_abandoned_unsent; 280 uint64_t sprstat_abandoned_sent; 281 }; 283 sprstat_assoc_id: This parameter is ignored for one-to-one style 284 sockets. For one-to-many style sockets this parameter indicates 285 for which association the user wants the information. It is an 286 error to use SCTP_{CURRENT|ALL|FUTURE}_ASSOC in sprstat_assoc_id. 288 sprstat_sid: This parameter is ignored. 290 sprstat_policy: This parameter indicates for which PR-SCTP policy 291 the user wants the information. It is an error to use 292 SCTP_PR_SCTP_NONE in sprstat_policy. If SCTP_PR_SCTP_ALL is used, 293 the counters provided are aggregated over all supported policies. 295 sprstat_abandoned_unsent: The number of user messages which have 296 been abandoned using the policy specified in sprstat_policy for 297 the association specified by sprstat_assoc_id, before any part of 298 the user message could be sent. 300 sprstat_abandoned_sent: The number of user messages which have been 301 abandoned using the policy specified in sprstat_policy for the 302 association specified by sprstat_assoc_id, after a part of the 303 user message has been sent. 305 There are separate counters for unsent and sent user messages because 306 the SCTP_SEND_FAILED_EVENT supports a similar differentiation. 307 Please note that an abandoned large user message requiring an SCTP 308 level fragmentation is reported in the sprstat_abandoned_sent counter 309 as soon as at least one fragment of it has been sent. Therefore each 310 abandoned user message is either counted in sprstat_abandoned_unsent 311 or sprstat_abandoned_sent. 313 If more detailed information about abandoned user messages is 314 required, the usage of the option described in Section 4.3 or the 315 subscription to the SCTP_SEND_FAILED_EVENT is recommended. 317 sctp_opt_info() needs to be extended to support SCTP_PR_ASSOC_STATUS. 319 4.5. Socket Option for Getting and Setting the PR-SCTP Support 320 (SCTP_PR_SUPPORTED) 322 This socket option allows the enabling or disabling of the 323 negotiation of PR-SCTP support for future associations. For existing 324 associations it allows to query whether PR-SCTP support was 325 negotiated or not on a particular association. 327 Whether PR-SCTP is enabled or not per default is implementation 328 specific. 330 This socket option uses IPPROTO_SCTP as its level and 331 SCTP_PR_SUPPORTED as its name. It can be used with getsockopt() and 332 setsockopt(). The socket option value uses the following structure 333 defined in [RFC6458]: 335 struct sctp_assoc_value { 336 sctp_assoc_t assoc_id; 337 uint32_t assoc_value; 338 }; 340 assoc_id: This parameter is ignored for one-to-one style sockets. 341 For one-to-many style sockets, this parameter indicates upon which 342 association the user is performing an action. The special 343 sctp_assoc_t SCTP_FUTURE_ASSOC can also be used, it is an error to 344 use SCTP_{CURRENT|ALL}_ASSOC in assoc_id. 346 assoc_value: A non-zero value encodes the enabling of PR-SCTP 347 whereas a value of 0 encodes the disabling of PR-SCTP. 349 sctp_opt_info() needs to be extended to support SCTP_PR_SUPPORTED. 351 5. IANA Considerations 353 This document requires no actions from IANA. 355 6. Security Considerations 357 This document does not add any additional security considerations in 358 addition to the ones given in [RFC4960], [RFC3758], and [RFC6458]. 359 As indicated in the Security Section of [RFC3758], transport layer 360 security in the form of TLS over SCTP (see [RFC3436]) can't be used 361 for PR-SCTP. However, DTLS over SCTP (see [RFC6083]) could be used 362 instead. If DTLS over SCTP as specified in [RFC6083] is used, the 363 security considerations of [RFC6083] do apply. It should also be 364 noted that using PR-SCTP for an SCTP association doesn't allow that 365 association to behave more aggressively than an SCTP association not 366 using PR-SCTP. 368 7. Acknowledgments 370 The authors wish to thank Benoit Claise, Spencer Dawkins, Stephen 371 Farrell, Gorry Fairhurst, Barry Leiba, Karen Egede Nielsen, Ka-Cheong 372 Poon, Dan Romascanu, Irene Ruengeler, Jamal Hadi Salim, Joseph 373 Salowey, Brian Trammell, and Vlad Yasevich for their invaluable 374 comments. 376 8. References 378 8.1. Normative References 380 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 381 Requirement Levels", BCP 14, RFC 2119, March 1997. 383 [RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P. 384 Conrad, "Stream Control Transmission Protocol (SCTP) 385 Partial Reliability Extension", RFC 3758, May 2004. 387 [RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC 388 4960, September 2007. 390 8.2. Informative References 392 [RFC3436] Jungmaier, A., Rescorla, E., and M. Tuexen, "Transport 393 Layer Security over Stream Control Transmission Protocol", 394 RFC 3436, December 2002. 396 [RFC6083] Tuexen, M., Seggelmann, R., and E. Rescorla, "Datagram 397 Transport Layer Security (DTLS) for Stream Control 398 Transmission Protocol (SCTP)", RFC 6083, January 2011. 400 [RFC6458] Stewart, R., Tuexen, M., Poon, K., Lei, P., and V. 401 Yasevich, "Sockets API Extensions for the Stream Control 402 Transmission Protocol (SCTP)", RFC 6458, December 2011. 404 [RFC7011] Claise, B., Trammell, B., and P. Aitken, "Specification of 405 the IP Flow Information Export (IPFIX) Protocol for the 406 Exchange of Flow Information", STD 77, RFC 7011, September 407 2013. 409 [I-D.ietf-rtcweb-data-channel] 410 Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data 411 Channels", draft-ietf-rtcweb-data-channel-13 (work in 412 progress), January 2015. 414 [IEEE.1003-1G.1997] 415 Institute of Electrical and Electronics Engineers, 416 "Protocol Independent Interfaces", IEEE Standard 1003.1G, 417 March 1997. 419 Authors' Addresses 421 Michael Tuexen 422 Muenster University of Applied Sciences 423 Stegerwaldstrasse 39 424 48565 Steinfurt 425 DE 427 Email: tuexen@fh-muenster.de 428 Robin Seggelmann 429 T-Systems International GmbH 430 Fasanenweg 5 431 70771 Leinfelden-Echterdingen 432 DE 434 Email: rfc@robin-seggelmann.com 436 Randall R. Stewart 437 Netflix, Inc. 438 Chapin, SC 29036 439 US 441 Email: randall@lakerest.net 443 Salvatore Loreto 444 Ericsson 445 Hirsalantie 11 446 Jorvas 02420 447 FI 449 Email: Salvatore.Loreto@ericsson.com