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Checking references for intended status: Informational ---------------------------------------------------------------------------- ** 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: Informational R. Seggelmann 5 Expires: October 10, 2014 T-Systems International GmbH 6 R. Stewart 7 Adara Networks 8 S. Loreto 9 Ericsson 10 April 8, 2014 12 Additional Policies for the Partial Reliability Extension of the Stream 13 Control Transmission Protocol 14 draft-ietf-tsvwg-sctp-prpolicies-02.txt 16 Abstract 18 This document defines policies for the Partial Reliability Extension 19 of the Stream Control Transmission Protocol (PR-SCTP) allowing to 20 limit the number of retransmissions or to prioritize user messages 21 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 October 10, 2014. 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. Additional PR-SCTP Policies . . . . . . . . . . . . . . . . . 3 59 2.1. Limited Retransmissions Policy . . . . . . . . . . . . . 3 60 2.2. Priority Policy . . . . . . . . . . . . . . . . . . . . . 3 61 3. Socket API Considerations . . . . . . . . . . . . . . . . . . 3 62 3.1. Data Types . . . . . . . . . . . . . . . . . . . . . . . 4 63 3.2. Support for Added PR-SCTP Policies . . . . . . . . . . . 4 64 3.3. Socket Option for Getting the PR-SCTP Status 65 (SCTP_PR_STATUS) . . . . . . . . . . . . . . . . . . . . 4 66 3.4. Socket Option for Getting and Setting the PR-SCTP Support 67 (SCTP_PR_SUPPORTED) . . . . . . . . . . . . . . . . . . . 5 68 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 69 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 70 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6 71 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 72 7.1. Normative References . . . . . . . . . . . . . . . . . . 6 73 7.2. Informative References . . . . . . . . . . . . . . . . . 6 74 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 76 1. Introduction 78 The SCTP Partial Reliability Extension (PR-SCTP) defined in [RFC3758] 79 provides a generic method for senders to abandon user messages. The 80 decision to abandon a user message is sender side only and the exact 81 condition is called a PR-SCTP policy. [RFC3758] also defines one 82 particular PR-SCTP policy, called Timed Reliability. This allows the 83 sender to specify a timeout for a user message after which the SCTP 84 stack abandons the user message. 86 This document specifies two additional PR-SCTP policies: 88 Limited Retransmission Policy: Allows to limit the number of 89 retransmissions. 91 Priority Policy: Allows to discard lower priority messages if space 92 for higher priority messages is needed in the send buffer. 94 2. Additional PR-SCTP Policies 96 This section defined two new PR-SCTP policies, one in each 97 subsection. 99 2.1. Limited Retransmissions Policy 101 Using the Limited Retransmission Policy allows the sender of a user 102 message to specify an upper limit for the number of retransmissions 103 for each DATA chunk of the given user messages. The sender must 104 abandon a user message if the number of retransmissions of any of the 105 DATA chunks of the user message would exceed the provided limit. 106 Please note that the number of retransmissions includes the fast and 107 the timer based retransmissions. 109 Limiting the number of retransmissions to 0 is allowed. This will 110 result in abandoning the message when it would get retransmitted for 111 the first time. The use of this setting provides a service similar 112 to UDP, which also does not send any retransmissions either. 114 The Limited Retransmissions Policy is used for data channels in the 115 WebRTC protocol stack. 117 2.2. Priority Policy 119 Using the Priority Policy allows the sender of a user message to 120 specify a priority. When storing a user message in the send buffer 121 while there is not enough available space, the SCTP stack may abandon 122 other user messages with a priority lower than the provided one. The 123 algorithm for selecting the message being abandoned is implementation 124 specific. 126 After lower priority messages have been abandoned high priority 127 messages can be transferred without blocking the send call (if used 128 in blocking mode) or failing the send call (if used in non-blocking 129 mode). 131 The Priority Policy can be used in the IPFIX protocol stack. See 132 [RFC7011] for more information. 134 3. Socket API Considerations 136 This section describes how the socket API defined in [RFC6458] is 137 extended to support the newly defined PR-SCTP policies and to provide 138 some statistical information. 140 3.1. Data Types 142 This section uses data types from [IEEE.1003-1G.1997]: uintN_t means 143 an unsigned integer of exactly N bits (e.g. uint16_t). This is the 144 same as in [RFC6458] 146 3.2. Support for Added PR-SCTP Policies 148 As defined in [RFC6458], the PR-SCTP policy is specified and 149 configured by using the following sctp_prinfo structure: 151 struct sctp_prinfo { 152 uint16_t pr_policy; 153 uint32_t pr_value; 154 }; 156 When the Limited Retransmission Policy described in Section 2.1 is 157 used, pr_policy has the value SCTP_PR_SCTP_RTX and the number of 158 retransmissions is given in pr_value. 160 For using the Priority Policy described in Section 2.2, pr_policy has 161 the value SCTP_PR_SCTP_PRIO. The priority is given in pr_value. The 162 value of zero is the highest priority and larger numbers in pr_value 163 denote lower priorities. 165 The following table summarizes the possible parameter settings 166 defined in [RFC6458] and this document: 168 +-------------------+---------------------------+---------------+ 169 | pr_policy | pr_value | Specification | 170 +-------------------+---------------------------+---------------+ 171 | SCTP_PR_SCTP_NONE | Ignored | [RFC6458] | 172 | SCTP_PR_SCTP_TTL | Lifetime in ms | [RFC6458] | 173 | SCTP_PR_SCTP_RTX | Number of retransmissions | Section 2.1 | 174 | SCTP_PR_SCTP_PRIO | Priority | Section 2.2 | 175 +-------------------+---------------------------+---------------+ 177 3.3. Socket Option for Getting the PR-SCTP Status (SCTP_PR_STATUS) 179 This socket option uses IPPROTO_SCTP as its level and SCTP_PR_STATUS 180 as its name. It can only be used with getsockopt(), but not with 181 setsockopt(). The socket option value uses the following structure: 183 struct sctp_prstatus { 184 sctp_assoc_t sprstat_assoc_id; 185 uint64_t sprstat_abandoned_unsent; 186 uint64_t sprstat_abandoned_sent; 187 }; 188 sprstat_assoc_id: This parameter is ignored for one-to-one style 189 sockets. For one-to-many style sockets this parameter indicates 190 for which association the user wants the information. It is an 191 error to use SCTP_{CURRENT|ALL|FUTURE}_ASSOC in sprstat_assoc_id. 193 sprstat_abandoned_unsent: The number of user messages which have 194 been abandoned, before any part of the user message could be sent. 196 sprstat_abandoned_sent: The number of user messages which have been 197 abandoned, after a part of the user message has been sent. 199 There are separate counters for unsent and sent user messages because 200 the SCTP_SEND_FAILED_EVENT supports a similar differentiation. 201 Please note that an abandoned large user message requiring an SCTP 202 level fragmentation is reported in the sprstat_abandoned_sent counter 203 as soon as at least one fragment of it has been sent. Therefore each 204 abandoned user message is either counted in sprstat_abandoned_unsent 205 or sprstat_abandoned_sent. 207 If more detailed information about abandoned user messages is 208 required, the subscription to the SCTP_SEND_FAILED_EVENT is 209 recommended. 211 sctp_opt_info() needs to be extended to support SCTP_PR_STATUS. 213 3.4. Socket Option for Getting and Setting the PR-SCTP Support 214 (SCTP_PR_SUPPORTED) 216 This socket option allows the enabling or disabling of the 217 negotiation of PR-SCTP support for future associations. For existing 218 associations it allows to query whether PR-SCTP support was 219 negotiated or not on particular associations. 221 Whether PR-SCTP is enabled or not per default is implementation 222 specific. 224 This socket option uses IPPROTO_SCTP as its level and 225 SCTP_PR_SUPPORTED as its name. It can be used with getsockopt() and 226 setsockopt(). The socket option value uses the following structure 227 defined in [RFC6458]: 229 struct sctp_assoc_value { 230 sctp_assoc_t assoc_id; 231 uint32_t assoc_value; 232 }; 234 assoc_id: This parameter is ignored for one-to-one style sockets. 235 For one-to-many style sockets, this parameter indicates upon which 236 association the user is performing an action. The special 237 sctp_assoc_t SCTP_FUTURE_ASSOC can also be used, it is an error to 238 use SCTP_{CURRENT|ALL}_ASSOC in assoc_id. 240 assoc_value: A non-zero value encodes the enabling of PR-SCTP 241 whereas a value of 0 encodes the disabling of PR-SCTP. 243 sctp_opt_info() needs to be extended to support SCTP_PR_SUPPORTED. 245 4. IANA Considerations 247 This document requires no actions from IANA. 249 5. Security Considerations 251 This document does not add any additional security considerations in 252 addition to the ones given in [RFC4960], [RFC3758], and [RFC6458]. 254 6. Acknowledgments 256 The authors wish to thank Karen Egede Nielsen, Ka-Cheong Poon, Irene 257 Ruengeler, Jamal Hadi Salim, and Vlad Yasevich for their invaluable 258 comments. 260 7. References 262 7.1. Normative References 264 [RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P. 265 Conrad, "Stream Control Transmission Protocol (SCTP) 266 Partial Reliability Extension", RFC 3758, May 2004. 268 [RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC 269 4960, September 2007. 271 7.2. Informative References 273 [RFC6458] Stewart, R., Tuexen, M., Poon, K., Lei, P., and V. 274 Yasevich, "Sockets API Extensions for the Stream Control 275 Transmission Protocol (SCTP)", RFC 6458, December 2011. 277 [RFC7011] Claise, B., Trammell, B., and P. Aitken, "Specification of 278 the IP Flow Information Export (IPFIX) Protocol for the 279 Exchange of Flow Information", STD 77, RFC 7011, September 280 2013. 282 [IEEE.1003-1G.1997] 283 Institute of Electrical and Electronics Engineers, 284 "Protocol Independent Interfaces", IEEE Standard 1003.1G, 285 March 1997. 287 Authors' Addresses 289 Michael Tuexen 290 Muenster University of Applied Sciences 291 Stegerwaldstrasse 39 292 48565 Steinfurt 293 DE 295 Email: tuexen@fh-muenster.de 297 Robin Seggelmann 298 T-Systems International GmbH 299 Fasanenweg 5 300 70771 Leinfelden-Echterdingen 301 DE 303 Email: robin.seggelmann@t-systems.com 305 Randall R. Stewart 306 Adara Networks 307 Chapin, SC 29036 308 US 310 Email: randall@lakerest.net 312 Salvatore Loreto 313 Ericsson 314 Hirsalantie 11 315 Jorvas 02420 316 FI 318 Email: Salvatore.Loreto@ericsson.com