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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: June 17, 2014 T-Systems International GmbH 6 R. Stewart 7 Adara Networks 8 S. Loreto 9 Ericsson 10 December 14, 2013 12 Additional Policies for the Partial Reliability Extension of the Stream 13 Control Transmission Protocol 14 draft-ietf-tsvwg-sctp-prpolicies-00.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 June 17, 2014. 40 Copyright Notice 42 Copyright (c) 2013 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 1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 2 59 1.2. Data Types . . . . . . . . . . . . . . . . . . . . . . . 2 60 2. Additional PR-SCTP Policies . . . . . . . . . . . . . . . . . 3 61 2.1. Limited Retransmissions Policy . . . . . . . . . . . . . 3 62 2.2. Priority Policy . . . . . . . . . . . . . . . . . . . . . 3 63 3. Socket API Considerations . . . . . . . . . . . . . . . . . . 3 64 3.1. Support for Added PR-SCTP Policies . . . . . . . . . . . 3 65 3.2. Socket Option for Getting the PR-SCTP Status 66 (SCTP_PR_STATUS) . . . . . . . . . . . . . . . . . . . . 4 67 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 68 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 69 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5 70 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 71 7.1. Normative References . . . . . . . . . . . . . . . . . . 5 72 7.2. Informative References . . . . . . . . . . . . . . . . . 5 73 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 75 1. Introduction 77 1.1. Overview 79 The SCTP Partial Reliability Extension (PR-SCTP) defined in [RFC3758] 80 provides a generic method for senders to abandon user messages. The 81 decision to abandon a user message is sender side only and the exact 82 condition is called a PR-SCTP policy. [RFC3758] also defines one 83 particular PR-SCTP policy, called Timed Reliability. This allows the 84 sender to specify a timeout for a user message after which the SCTP 85 stack abandons the user message. 87 This document specifies two additional PR-SCTP policies: 89 Limited Retransmission Policy: Allows to limit the number of 90 retransmissions. 92 Priority Policy: Allows to discard lower priority messages if space 93 for higher priority messages is needed in the send buffer. 95 1.2. Data Types 96 This documents uses data types from Draft 6.6 (March 1997) of POSIX 97 1003.1g: uintN_t means an unsigned integer of exactly N bits (e.g. 98 uint16_t). This is the same as in [RFC6458] 100 2. Additional PR-SCTP Policies 102 2.1. Limited Retransmissions Policy 104 Using the Limited Retransmission Policy allows the sender of a user 105 message to specify an upper limit for the number of retransmissions 106 for each DATA chunk of the given user messages. The sender must 107 abandon a user message if the number of retransmissions of any of the 108 DATA chunks of the user message would exceed the provided limit. 109 Please note that the number of retransmissions includes the fast and 110 the timer based retransmissions. 112 Limiting the number of retransmissions to 0 is allowed. This 113 provides a service similar to UDP, which also does not send any 114 retransmissions either. 116 The Limited Retransmissions Policy is used for data channels in the 117 RTCWeb protocol stack. 119 2.2. Priority Policy 121 Using the Priority Policy allows the sender of a user message to 122 specify a priority. When storing a user message in the send buffer 123 while there is not enough available space, the SCTP stack may abandon 124 other user messages with a priority lower than the provided one. 126 After lower priority messages have been abandoned high priority 127 messages can be transferred without blocking the send() call. 129 The Priority Policy can be used in the IPFIX protocol stack. See 130 [RFC7011] for more information. 132 3. Socket API Considerations 134 This section describes how the socket API defined in [RFC6458] is 135 extended to support the newly defined PR-SCTP policies and to provide 136 some statistical information. 138 Please note that this section is informational only. 140 3.1. Support for Added PR-SCTP Policies 142 As defined in [RFC6458], the PR-SCTP policy is specified and 143 configured by using the following sctp_prinfo structure: 145 struct sctp_prinfo { 146 uint16_t pr_policy; 147 uint32_t pr_value; 148 }; 150 When the Limited Retransmission Policy described in Section 2.1 is 151 used, pr_policy has the value SCTP_PR_SCTP_RTX and the number of 152 retransmissions is given in pr_value. 154 For using the Priority Policy described in Section 2.2, pr_policy has 155 the value SCTP_PR_SCTP_PRIO. The priority is given in pr_value. The 156 value of zero is the highest priority and larger numbers in pr_value 157 denote lower priorities. 159 The following table summarizes the possible parameter settings 160 defined in [RFC6458] and this document: 162 +-------------------+---------------------------+---------------+ 163 | pr_policy | pr_value | Specification | 164 +-------------------+---------------------------+---------------+ 165 | SCTP_PR_SCTP_NONE | Ignored | [RFC6458] | 166 | SCTP_PR_SCTP_TTL | Lifetime in ms | [RFC6458] | 167 | SCTP_PR_SCTP_RTX | Number of retransmissions | Section 2.1 | 168 | SCTP_PR_SCTP_PRIO | Priority | Section 2.2 | 169 +-------------------+---------------------------+---------------+ 171 3.2. Socket Option for Getting the PR-SCTP Status (SCTP_PR_STATUS) 173 This socket option uses IPPROTO_SCTP as its level and SCTP_PR_STATUS 174 as its name. It can only be used with getsockopt(), but not with 175 setsockopt(). The socket option value uses the following structure: 177 struct sctp_prstatus { 178 sctp_assoc_t sprstat_assoc_id; 179 uint32_t sprstat_abandoned_unsent; 180 uint32_t sprstat_abandoned_sent; 181 }; 183 sprstat_assoc_id: This parameter is ignored for one-to-one style 184 sockets. For one-to-many style sockets this parameter indicates 185 for which association the user wants the information. It is an 186 error to use SCTP_{CURRENT|ALL|FUTURE}_ASSOC in sprstat_assoc_id 188 sprstat_abandoned_unsent: The number of user messages which have 189 been abandoned, before any part of the user message could be sent. 191 sprstat_abandoned_sent: The number of user messages which have been 192 abandoned, after a part of the user message has been sent. 194 There are separate counters for unsent and sent user messages because 195 the SCTP_SEND_FAILED_EVENT supports a similar differentiation. 196 Please note that an abandoned large user messages requiring an SCTP 197 level fragmentation is reported in the sprstat_abandoned_sent counter 198 as soon as at least one fragment of it has been sent. Therefore each 199 abandoned user messages is either counted in sprstat_abandoned_unsent 200 or sprstat_abandoned_sent. 202 If more detailed information about abandoned user messages is 203 required, the subscription to the SCTP_SEND_FAILED_EVENT is 204 recommended. 206 sctp_opt_info() needs to be extended to support SCTP_PR_STATUS. 208 4. IANA Considerations 210 This document requires no actions from IANA. 212 5. Security Considerations 214 This document does not add any additional security considerations in 215 addition to the ones given in [RFC4960], [RFC3758], and [RFC6458]. 217 6. Acknowledgments 219 The authors wish to thank Irene Ruengeler, Jamal Hadi Salim, and Vlad 220 Yasevich for there invaluable comments. 222 7. References 224 7.1. Normative References 226 [RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P. 227 Conrad, "Stream Control Transmission Protocol (SCTP) 228 Partial Reliability Extension", RFC 3758, May 2004. 230 [RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC 231 4960, September 2007. 233 7.2. Informative References 235 [RFC6458] Stewart, R., Tuexen, M., Poon, K., Lei, P., and V. 236 Yasevich, "Sockets API Extensions for the Stream Control 237 Transmission Protocol (SCTP)", RFC 6458, December 2011. 239 [RFC7011] Claise, B., Trammell, B., and P. Aitken, "Specification of 240 the IP Flow Information Export (IPFIX) Protocol for the 241 Exchange of Flow Information", STD 77, RFC 7011, September 242 2013. 244 Authors' Addresses 246 Michael Tuexen 247 Muenster University of Applied Sciences 248 Stegerwaldstrasse 39 249 48565 Steinfurt 250 DE 252 Email: tuexen@fh-muenster.de 254 Robin Seggelmann 255 T-Systems International GmbH 256 Fasanenweg 5 257 70771 Leinfelden-Echterdingen 258 DE 260 Email: robin.seggelmann@t-systems.com 262 Randall R. Stewart 263 Adara Networks 264 Chapin, SC 29036 265 US 267 Email: randall@lakerest.net 269 Salvatore Loreto 270 Ericsson 271 Hirsalantie 11 272 Jorvas 02420 273 FI 275 Email: Salvatore.Loreto@ericsson.com