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(See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (July 10, 2009) is 5397 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references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 4960 (Obsoleted by RFC 9260) == Outdated reference: A later version (-32) exists of draft-ietf-tsvwg-sctpsocket-19 Summary: 2 errors (**), 0 flaws (~~), 2 warnings (==), 3 comments (--).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 Updates: 4960 (if approved) Muenster Univ. of Applied Sciences 5 Intended status: Standards Track R. Stewart 6 Expires: January 11, 2010 Researcher 7 July 10, 2009 9 SACK-IMMEDIATELY extension for the Stream Control Transmission Protocol 10 draft-tuexen-tsvwg-sctp-sack-immediately-02.txt 12 Status of this Memo 14 This Internet-Draft is submitted to IETF in full conformance with the 15 provisions of BCP 78 and BCP 79. 17 Internet-Drafts are working documents of the Internet Engineering 18 Task Force (IETF), its areas, and its working groups. Note that 19 other groups may also distribute working documents as Internet- 20 Drafts. 22 Internet-Drafts are draft documents valid for a maximum of six months 23 and may be updated, replaced, or obsoleted by other documents at any 24 time. It is inappropriate to use Internet-Drafts as reference 25 material or to cite them other than as "work in progress." 27 The list of current Internet-Drafts can be accessed at 28 http://www.ietf.org/ietf/1id-abstracts.txt. 30 The list of Internet-Draft Shadow Directories can be accessed at 31 http://www.ietf.org/shadow.html. 33 This Internet-Draft will expire on January 11, 2010. 35 Copyright Notice 37 Copyright (c) 2009 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents in effect on the date of 42 publication of this document (http://trustee.ietf.org/license-info). 43 Please review these documents carefully, as they describe your rights 44 and restrictions with respect to this document. 46 Abstract 48 This document defines a method for a sender of a DATA chunk to 49 indicate that the corresponding SACK chunk should be sent back 50 immediately. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 55 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 3 56 3. The I-bit in the DATA Chunk Header . . . . . . . . . . . . . . 3 57 4. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . 4 58 4.1. Sender Side Considerations . . . . . . . . . . . . . . . . 4 59 4.2. Receiver Side Considerations . . . . . . . . . . . . . . . 4 60 5. Interoperability Considerations . . . . . . . . . . . . . . . . 4 61 6. Socket API Considerations . . . . . . . . . . . . . . . . . . . 4 62 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 63 8. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 64 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 65 9.1. Normative References . . . . . . . . . . . . . . . . . . . 5 66 9.2. Informative References . . . . . . . . . . . . . . . . . . 5 67 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 69 1. Introduction 71 [RFC4960] states that an SCTP implementation should use delayed 72 SACKs. In combination with the Nagle algorithm, reduced congestion 73 windows after timeouts, the handling of the SHUTDOWN-PENDING state, 74 or other situations this might result in reduced performance of the 75 protocol. 77 This document describes a simple extension of the SCTP DATA chunk by 78 defining a new flag, the I-bit. The sender indicates by setting this 79 bit that the corresponding SACK chunk should be sent back without 80 delaying it. 82 2. Conventions 84 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 85 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 86 document are to be interpreted as described in [RFC2119]. 88 3. The I-bit in the DATA Chunk Header 90 The following Figure 1 shows the extended DATA chunk. 92 0 1 2 3 93 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 94 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 95 | Type = 0 | Res |I|U|B|E| Length | 96 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 97 | TSN | 98 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 99 | Stream Identifier | Stream Sequence Number | 100 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 101 | Payload Protocol Identifier | 102 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 103 \ \ 104 / User Data / 105 \ \ 106 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 108 Figure 1 110 The only difference between the DATA chunk in Figure 1 and the DATA 111 chunk defined in [RFC4960] is the addition of the I-bit in the flags 112 field of the chunk header. 114 4. Procedures 116 4.1. Sender Side Considerations 118 Whenever the sender of a DATA chunk can benefit from the 119 corresponding SACK chunk being sent back without delay, the sender 120 MAY set the I-bit in the DATA chunk header. 122 Reasons for setting the I-bit include 124 o The sender has not enough queued user data to send the remaining 125 DATA chunks due to the Nagle algorithm. 127 o The sending of a DATA chunk fills the congestion or receiver 128 window. 130 o The sender is in the SHUTDOWN-PENDING state. 132 o The sender has reduced its RTO.Min such that a retransmission 133 timeout will occur if the receiver delays its SACK. 135 o The application requests to set the I-bit of the last DATA chunk 136 of a user message when providing the user message to the SCTP 137 implementation. 139 4.2. Receiver Side Considerations 141 On reception of an SCTP packet containing a DATA chunk with the I-bit 142 set, the receiver SHOULD NOT delay the sending of the corresponding 143 SACK chunk and SHOULD send it back immediately. 145 5. Interoperability Considerations 147 According to [RFC4960] a receiver of a DATA chunk with the I-bit set 148 should ignore this bit when it does not support the extension 149 described in this document. Since the sender of the DATA chunk is 150 able to handle this case, there is no requirement for negotiating the 151 feature described in this document. 153 6. Socket API Considerations 155 A socket API implementation based on [I-D.ietf-tsvwg-sctpsocket] 156 SHOULD be extended by supporting a flag called SCTP_SACK_IMMEDIATELY, 157 which can be set in the sinfo_flags field of the struct 158 sctp_sndrcvinfo structure. 160 If the SCTP_SACK_IMMEDIATELY flag is set when sending a user message, 161 the I-bit of the last DATA chunk of the corresponding user message 162 MUST be set. 164 7. IANA Considerations 166 [NOTE to RFC-Editor: 168 "RFCXXXX" is to be replaced by the RFC number you assign this 169 document. 171 ] 173 IANA should change the Reference in the CHUNK TYPES Registry 174 available at sctp-parameters [1] for the ID value '0' and Chunk Type 175 'Payload Data (DATA)' from RFC4960 to RFCXXXX. 177 8. Security Considerations 179 This document does not add any additional security considerations in 180 addition to the ones given in [RFC4960]. 182 9. References 184 9.1. Normative References 186 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 187 Requirement Levels", BCP 14, RFC 2119, March 1997. 189 [RFC4960] Stewart, R., "Stream Control Transmission Protocol", 190 RFC 4960, September 2007. 192 9.2. Informative References 194 [I-D.ietf-tsvwg-sctpsocket] 195 Stewart, R., Poon, K., Tuexen, M., Yasevich, V., and P. 196 Lei, "Sockets API Extensions for Stream Control 197 Transmission Protocol (SCTP)", 198 draft-ietf-tsvwg-sctpsocket-19 (work in progress), 199 February 2009. 201 URIs 203 [1] 205 Authors' Addresses 207 Michael Tuexen 208 Muenster Univ. of Applied Sciences 209 Stegerwaldstr. 39 210 48565 Steinfurt 211 Germany 213 Email: tuexen@fh-muenster.de 215 Irene Ruengeler 216 Muenster Univ. of Applied Sciences 217 Stegerwaldstr. 39 218 48565 Steinfurt 219 Germany 221 Email: i.ruengeler@fh-muenster.de 223 Randall R. Stewart 224 Researcher 225 Chapin, SC 29036 226 USA 228 Phone: 229 Email: randall@lakerest.net