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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references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 4960 (Obsoleted by RFC 9260) == Outdated reference: A later version (-32) exists of draft-ietf-tsvwg-sctpsocket-21 Summary: 2 errors (**), 0 flaws (~~), 2 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group M. Tuexen 3 Internet-Draft I. Ruengeler 4 Intended status: Standards Track Muenster Univ. of Applied Sciences 5 Expires: September 3, 2010 R. Stewart 6 Researcher 7 March 2, 2010 9 SACK-IMMEDIATELY extension for the Stream Control Transmission Protocol 10 draft-tuexen-tsvwg-sctp-sack-immediately-03.txt 12 Abstract 14 This document defines a method for a sender of a DATA chunk to 15 indicate that the corresponding SACK chunk should be sent back 16 immediately. 18 Status of this Memo 20 This Internet-Draft is submitted to IETF in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF), its areas, and its working groups. Note that 25 other groups may also distribute working documents as Internet- 26 Drafts. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 The list of current Internet-Drafts can be accessed at 34 http://www.ietf.org/ietf/1id-abstracts.txt. 36 The list of Internet-Draft Shadow Directories can be accessed at 37 http://www.ietf.org/shadow.html. 39 This Internet-Draft will expire on September 3, 2010. 41 Copyright Notice 43 Copyright (c) 2010 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (http://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 59 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 3 60 3. The I-bit in the DATA Chunk Header . . . . . . . . . . . . . . 3 61 4. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . 4 62 4.1. Sender Side Considerations . . . . . . . . . . . . . . . . 4 63 4.2. Receiver Side Considerations . . . . . . . . . . . . . . . 4 64 5. Interoperability Considerations . . . . . . . . . . . . . . . . 4 65 6. Socket API Considerations . . . . . . . . . . . . . . . . . . . 4 66 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 67 8. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 68 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 69 9.1. Normative References . . . . . . . . . . . . . . . . . . . 5 70 9.2. Informative References . . . . . . . . . . . . . . . . . . 5 71 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 73 1. Introduction 75 [RFC4960] states that an SCTP implementation should use delayed 76 SACKs. In combination with the Nagle algorithm, reduced congestion 77 windows after timeouts, the handling of the SHUTDOWN-PENDING state, 78 or other situations this might result in reduced performance of the 79 protocol. 81 This document describes a simple extension of the SCTP DATA chunk by 82 defining a new flag, the I-bit. The sender indicates by setting this 83 bit that the corresponding SACK chunk should be sent back without 84 delaying it. 86 2. Conventions 88 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 89 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 90 document are to be interpreted as described in [RFC2119]. 92 3. The I-bit in the DATA Chunk Header 94 The following Figure 1 shows the extended DATA chunk. 96 0 1 2 3 97 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 98 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 99 | Type = 0 | Res |I|U|B|E| Length | 100 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 101 | TSN | 102 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 103 | Stream Identifier | Stream Sequence Number | 104 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 105 | Payload Protocol Identifier | 106 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 107 \ \ 108 / User Data / 109 \ \ 110 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 112 Figure 1 114 The only difference between the DATA chunk in Figure 1 and the DATA 115 chunk defined in [RFC4960] is the addition of the I-bit in the flags 116 field of the chunk header. 118 4. Procedures 120 4.1. Sender Side Considerations 122 Whenever the sender of a DATA chunk can benefit from the 123 corresponding SACK chunk being sent back without delay, the sender 124 MAY set the I-bit in the DATA chunk header. 126 Reasons for setting the I-bit include 128 o The sender has not enough queued user data to send the remaining 129 DATA chunks due to the Nagle algorithm. 131 o The sending of a DATA chunk fills the congestion or receiver 132 window. 134 o The sender is in the SHUTDOWN-PENDING state. 136 o The sender has reduced its RTO.Min such that a retransmission 137 timeout will occur if the receiver delays its SACK. 139 o The application requests to set the I-bit of the last DATA chunk 140 of a user message when providing the user message to the SCTP 141 implementation. 143 4.2. Receiver Side Considerations 145 On reception of an SCTP packet containing a DATA chunk with the I-bit 146 set, the receiver SHOULD NOT delay the sending of the corresponding 147 SACK chunk and SHOULD send it back immediately. 149 5. Interoperability Considerations 151 According to [RFC4960] a receiver of a DATA chunk with the I-bit set 152 should ignore this bit when it does not support the extension 153 described in this document. Since the sender of the DATA chunk is 154 able to handle this case, there is no requirement for negotiating the 155 feature described in this document. 157 6. Socket API Considerations 159 A socket API implementation based on [I-D.ietf-tsvwg-sctpsocket] 160 SHOULD be extended by supporting a flag called SCTP_SACK_IMMEDIATELY, 161 which can be set in the sinfo_flags field of the struct 162 sctp_sndrcvinfo structure. 164 If the SCTP_SACK_IMMEDIATELY flag is set when sending a user message, 165 the I-bit of the last DATA chunk of the corresponding user message 166 MUST be set. 168 7. IANA Considerations 170 [NOTE to RFC-Editor: 172 "RFCXXXX" is to be replaced by the RFC number you assign this 173 document. 175 ] 177 Following the chunk flag registeration procedure defined in 178 [I-D.tuexen-tsvwg-sctp-chunk-flags] IANA should register a new bit, 179 the I-bit, for the DATA chunk. The suggested value is 0x08. The 180 reference for the new chunk flag in the chunk flags table for the 181 DATA chunk available at sctp-parameters [1] should be RFCXXXX. 183 8. Security Considerations 185 This document does not add any additional security considerations in 186 addition to the ones given in [RFC4960]. 188 9. References 190 9.1. Normative References 192 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 193 Requirement Levels", BCP 14, RFC 2119, March 1997. 195 [RFC4960] Stewart, R., "Stream Control Transmission Protocol", 196 RFC 4960, September 2007. 198 [I-D.tuexen-tsvwg-sctp-chunk-flags] 199 Tuexen, M. and R. Stewart, "Stream Control Transmission 200 Protocol Chunk Flags Registration", 201 draft-tuexen-tsvwg-sctp-chunk-flags-00 (work in progress), 202 March 2010. 204 9.2. Informative References 206 [I-D.ietf-tsvwg-sctpsocket] 207 Stewart, R., Poon, K., Tuexen, M., Yasevich, V., and P. 208 Lei, "Sockets API Extensions for Stream Control 209 Transmission Protocol (SCTP)", 210 draft-ietf-tsvwg-sctpsocket-21 (work in progress), 211 February 2010. 213 URIs 215 [1] 217 Authors' Addresses 219 Michael Tuexen 220 Muenster Univ. of Applied Sciences 221 Stegerwaldstr. 39 222 48565 Steinfurt 223 Germany 225 Email: tuexen@fh-muenster.de 227 Irene Ruengeler 228 Muenster Univ. of Applied Sciences 229 Stegerwaldstr. 39 230 48565 Steinfurt 231 Germany 233 Email: i.ruengeler@fh-muenster.de 235 Randall R. Stewart 236 Researcher 237 Chapin, SC 29036 238 USA 240 Phone: 241 Email: randall@lakerest.net