idnits 2.17.1 draft-ietf-tsvwg-sctp-prpolicies-06.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 (December 10, 2014) is 3422 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references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 4960 (Obsoleted by RFC 9260) == Outdated reference: A later version (-13) exists of draft-ietf-rtcweb-data-channel-12 Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 1 comment (--).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: June 13, 2015 T-Systems International GmbH 6 R. Stewart 7 Netflix, Inc. 8 S. Loreto 9 Ericsson 10 December 10, 2014 12 Additional Policies for the Partial Reliability Extension of the Stream 13 Control Transmission Protocol 14 draft-ietf-tsvwg-sctp-prpolicies-06.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 June 13, 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] 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 The Limited Retransmissions Policy can be used with data channels in 132 the WebRTC protocol stack. See [I-D.ietf-rtcweb-data-channel] for 133 more information. 135 3.2. Priority Policy 137 Using the Priority Policy allows the sender of a user message to 138 specify a priority. When storing a user message in the send buffer 139 while there is not enough available space, the SCTP stack at the 140 sender side MAY abandon other user messages of the same SCTP 141 association with a priority lower than the provided one. The 142 algorithm for selecting the message being abandoned is implementation 143 specific. 145 After lower priority messages have been abandoned high priority 146 messages can be transferred without the send call blocking (if used 147 in blocking mode) or the send call failing (if used in non-blocking 148 mode). 150 The Priority Policy can be used in the IPFIX protocol stack. See 151 [RFC7011] for more information. 153 4. Socket API Considerations 155 This section describes how the socket API defined in [RFC6458] is 156 extended to support the newly defined PR-SCTP policies, to provide 157 some statistical information and to control the negotiation of the 158 PR-SCTP extension during the SCTP association setup. 160 Please note that this section is informational only. 162 4.1. Data Types 164 This section uses data types from [IEEE.1003-1G.1997]: uintN_t means 165 an unsigned integer of exactly N bits (e.g. uint16_t). This is the 166 same as in [RFC6458]. 168 4.2. Support for Added PR-SCTP Policies 170 As defined in [RFC6458], the PR-SCTP policy is specified and 171 configured by using the following sctp_prinfo structure: 173 struct sctp_prinfo { 174 uint16_t pr_policy; 175 uint32_t pr_value; 176 }; 178 When the Limited Retransmission Policy described in Section 3.1 is 179 used, pr_policy has the value SCTP_PR_SCTP_RTX and the number of 180 retransmissions is given in pr_value. 182 When using the Priority Policy described in Section 3.2, pr_policy 183 has the value SCTP_PR_SCTP_PRIO. The priority is given in pr_value. 184 The value of zero is the highest priority and larger numbers in 185 pr_value denote lower priorities. 187 The following table summarizes the possible parameter settings 188 defined in [RFC6458] and this document: 190 +-------------------+---------------------------+---------------+ 191 | pr_policy | pr_value | Specification | 192 +-------------------+---------------------------+---------------+ 193 | SCTP_PR_SCTP_NONE | Ignored | [RFC6458] | 194 | SCTP_PR_SCTP_TTL | Lifetime in ms | [RFC6458] | 195 | SCTP_PR_SCTP_RTX | Number of retransmissions | Section 3.1 | 196 | SCTP_PR_SCTP_PRIO | Priority | Section 3.2 | 197 +-------------------+---------------------------+---------------+ 199 4.3. Socket Option for Getting the Stream Specific PR-SCTP Status 200 (SCTP_PR_STREAM_STATUS) 202 This socket option uses IPPROTO_SCTP as its level and 203 SCTP_PR_STREAM_STATUS as its name. It can only be used with 204 getsockopt(), but not with setsockopt(). The socket option value 205 uses the following structure: 207 struct sctp_prstatus { 208 sctp_assoc_t sprstat_assoc_id; 209 uint16_t sprstat_sid; 210 uint16_t sprstat_policy; 211 uint64_t sprstat_abandoned_unsent; 212 uint64_t sprstat_abandoned_sent; 213 }; 215 sprstat_assoc_id: This parameter is ignored for one-to-one style 216 sockets. For one-to-many style sockets this parameter indicates 217 for which association the user wants the information. It is an 218 error to use SCTP_{CURRENT|ALL|FUTURE}_ASSOC in sprstat_assoc_id. 220 sprstat_sid: This parameter indicates for which outgoing SCTP stream 221 the user wants the information. 223 sprstat_policy: This parameter indicates for which PR-SCTP policy 224 the user wants the information. It is an error to use 225 SCTP_PR_SCTP_NONE in sprstat_policy. If SCTP_PR_SCTP_ALL is used, 226 the counters provided are aggregated over all supported policies. 228 sprstat_abandoned_unsent: The number of user messages which have 229 been abandoned using the policy specified in sprstat_policy on the 230 stream specified in sprstat_sid for the association specified by 231 sprstat_assoc_id, before any part of the user message could be 232 sent. 234 sprstat_abandoned_sent: The number of user messages which have been 235 abandoned using the policy specified in sprstat_policy on the 236 stream specified in sprstat_sid for the association specified by 237 sprstat_assoc_id, after a part of the user message has been sent. 239 There are separate counters for unsent and sent user messages because 240 the SCTP_SEND_FAILED_EVENT supports a similar differentiation. 241 Please note that an abandoned large user message requiring an SCTP 242 level fragmentation is reported in the sprstat_abandoned_sent counter 243 as soon as at least one fragment of it has been sent. Therefore each 244 abandoned user message is either counted in sprstat_abandoned_unsent 245 or sprstat_abandoned_sent. 247 If more detailed information about abandoned user messages is 248 required, the subscription to the SCTP_SEND_FAILED_EVENT is 249 recommended. Please note that some implementations might choose not 250 to support this option, since it increases the resources needed for 251 an outgoing SCTP stream. For the same reasons, some implementations 252 might only support using SCTP_PR_SCTP_ALL in sprstat_policy. 254 sctp_opt_info() needs to be extended to support 255 SCTP_PR_STREAM_STATUS. 257 4.4. Socket Option for Getting the Association Specific PR-SCTP Status 258 (SCTP_PR_ASSOC_STATUS) 260 This socket option uses IPPROTO_SCTP as its level and 261 SCTP_PR_ASSOC_STATUS as its name. It can only be used with 262 getsockopt(), but not with setsockopt(). The socket option value 263 uses the same structure as described in Section 4.3: 265 struct sctp_prstatus { 266 sctp_assoc_t sprstat_assoc_id; 267 uint16_t sprstat_sid; 268 uint16_t sprstat_policy; 269 uint64_t sprstat_abandoned_unsent; 270 uint64_t sprstat_abandoned_sent; 271 }; 273 sprstat_assoc_id: This parameter is ignored for one-to-one style 274 sockets. For one-to-many style sockets this parameter indicates 275 for which association the user wants the information. It is an 276 error to use SCTP_{CURRENT|ALL|FUTURE}_ASSOC in sprstat_assoc_id. 278 sprstat_sid: This parameter is ignored. 280 sprstat_policy: This parameter indicates for which PR-SCTP policy 281 the user wants the information. It is an error to use 282 SCTP_PR_SCTP_NONE in sprstat_policy. If SCTP_PR_SCTP_ALL is used, 283 the counters provided are aggregated over all supported policies. 285 sprstat_abandoned_unsent: The number of user messages which have 286 been abandoned using the policy specified in sprstat_policy for 287 the association specified by sprstat_assoc_id, before any part of 288 the user message could be sent. 290 sprstat_abandoned_sent: The number of user messages which have been 291 abandoned using the policy specified in sprstat_policy for the 292 association specified by sprstat_assoc_id, after a part of the 293 user message has been sent. 295 There are separate counters for unsent and sent user messages because 296 the SCTP_SEND_FAILED_EVENT supports a similar differentiation. 297 Please note that an abandoned large user message requiring an SCTP 298 level fragmentation is reported in the sprstat_abandoned_sent counter 299 as soon as at least one fragment of it has been sent. Therefore each 300 abandoned user message is either counted in sprstat_abandoned_unsent 301 or sprstat_abandoned_sent. 303 If more detailed information about abandoned user messages is 304 required, the usage of the option described in Section 4.3 or the 305 subscription to the SCTP_SEND_FAILED_EVENT is recommended. 307 sctp_opt_info() needs to be extended to support SCTP_PR_ASSOC_STATUS. 309 4.5. Socket Option for Getting and Setting the PR-SCTP Support 310 (SCTP_PR_SUPPORTED) 312 This socket option allows the enabling or disabling of the 313 negotiation of PR-SCTP support for future associations. For existing 314 associations it allows to query whether PR-SCTP support was 315 negotiated or not on a particular association. 317 Whether PR-SCTP is enabled or not per default is implementation 318 specific. 320 This socket option uses IPPROTO_SCTP as its level and 321 SCTP_PR_SUPPORTED as its name. It can be used with getsockopt() and 322 setsockopt(). The socket option value uses the following structure 323 defined in [RFC6458]: 325 struct sctp_assoc_value { 326 sctp_assoc_t assoc_id; 327 uint32_t assoc_value; 328 }; 330 assoc_id: This parameter is ignored for one-to-one style sockets. 331 For one-to-many style sockets, this parameter indicates upon which 332 association the user is performing an action. The special 333 sctp_assoc_t SCTP_FUTURE_ASSOC can also be used, it is an error to 334 use SCTP_{CURRENT|ALL}_ASSOC in assoc_id. 336 assoc_value: A non-zero value encodes the enabling of PR-SCTP 337 whereas a value of 0 encodes the disabling of PR-SCTP. 339 sctp_opt_info() needs to be extended to support SCTP_PR_SUPPORTED. 341 5. IANA Considerations 343 This document requires no actions from IANA. 345 6. Security Considerations 347 This document does not add any additional security considerations in 348 addition to the ones given in [RFC4960], [RFC3758], and [RFC6458]. 349 As indicated in the Security Section of [RFC3758], transport layer 350 security in the form of TLS over SCTP (see [RFC3436]) can't be used 351 for PR-SCTP. However, DTLS over SCTP (see [RFC6083]) could be used 352 instead. If DTLS over SCTP as specified in [RFC6083] is used, the 353 security considerations of [RFC6083] do apply. It should also be 354 noted that using PR-SCTP for an SCTP association doesn't allow that 355 association to behave more aggressively than an SCTP association not 356 using PR-SCTP. 358 7. Acknowledgments 360 The authors wish to thank Spencer Dawkins, Gorry Fairhurst, Karen 361 Egede Nielsen, Ka-Cheong Poon, Dan Romascanu, Irene Ruengeler, Jamal 362 Hadi Salim, Joseph Salowey, and Vlad Yasevich for their invaluable 363 comments. 365 8. References 367 8.1. Normative References 369 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 370 Requirement Levels", BCP 14, RFC 2119, March 1997. 372 [RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P. 373 Conrad, "Stream Control Transmission Protocol (SCTP) 374 Partial Reliability Extension", RFC 3758, May 2004. 376 [RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC 377 4960, September 2007. 379 8.2. Informative References 381 [RFC3436] Jungmaier, A., Rescorla, E., and M. Tuexen, "Transport 382 Layer Security over Stream Control Transmission Protocol", 383 RFC 3436, December 2002. 385 [RFC6083] Tuexen, M., Seggelmann, R., and E. Rescorla, "Datagram 386 Transport Layer Security (DTLS) for Stream Control 387 Transmission Protocol (SCTP)", RFC 6083, January 2011. 389 [RFC6458] Stewart, R., Tuexen, M., Poon, K., Lei, P., and V. 390 Yasevich, "Sockets API Extensions for the Stream Control 391 Transmission Protocol (SCTP)", RFC 6458, December 2011. 393 [RFC7011] Claise, B., Trammell, B., and P. Aitken, "Specification of 394 the IP Flow Information Export (IPFIX) Protocol for the 395 Exchange of Flow Information", STD 77, RFC 7011, September 396 2013. 398 [I-D.ietf-rtcweb-data-channel] 399 Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data 400 Channels", draft-ietf-rtcweb-data-channel-12 (work in 401 progress), September 2014. 403 [IEEE.1003-1G.1997] 404 Institute of Electrical and Electronics Engineers, 405 "Protocol Independent Interfaces", IEEE Standard 1003.1G, 406 March 1997. 408 Authors' Addresses 410 Michael Tuexen 411 Muenster University of Applied Sciences 412 Stegerwaldstrasse 39 413 48565 Steinfurt 414 DE 416 Email: tuexen@fh-muenster.de 418 Robin Seggelmann 419 T-Systems International GmbH 420 Fasanenweg 5 421 70771 Leinfelden-Echterdingen 422 DE 424 Email: rfc@robin-seggelmann.com 425 Randall R. Stewart 426 Netflix, Inc. 427 Chapin, SC 29036 428 US 430 Email: randall@lakerest.net 432 Salvatore Loreto 433 Ericsson 434 Hirsalantie 11 435 Jorvas 02420 436 FI 438 Email: Salvatore.Loreto@ericsson.com