Network Working Group M. Tuexen Internet-Draft I. Ruengeler Intended status: Standards Track Muenster Univ. of Applied Sciences Expires: January 6, 2009 R. Stewart The Resource Group July 5, 2008 SACK-IMMEDIATELY extension for the Stream Control Transmission Protocol draft-tuexen-tsvwg-sctp-sack-immediately-00.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on January 6, 2009. Abstract This document defines a method for a sender of a DATA chunk to indicate that the corresponding SACK chunk should be sent back immediately. Tuexen, et al. Expires January 6, 2009 [Page 1] Internet-Draft SACK-IMMEDIATELY July 2008 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. The I-bit in the DATA Chunk Header . . . . . . . . . . . . . . 3 4. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.1. Sender Side Considerations . . . . . . . . . . . . . . . . 4 4.2. Receiver Side Considerations . . . . . . . . . . . . . . . 4 5. Interoperability Considerations . . . . . . . . . . . . . . . . 4 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 8. Normative References . . . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 5 Intellectual Property and Copyright Statements . . . . . . . . . . 6 Tuexen, et al. Expires January 6, 2009 [Page 2] Internet-Draft SACK-IMMEDIATELY July 2008 1. Introduction [RFC4960] states that an SCTP implementation should use delayed SACKs. In combination with the Nagle algorithm, reduced congestion windows after timeouts, the handling of the SHUTDOWN-SENDING state, or other situations this might result in reduced performance of the protocol. This document describes a simple extension of the SCTP DATA chunk by defining a new flag, the I-bit. The sender indicates by setting this bit that the corresponding SACK chunk should be sent back without delaying it. 2. Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 3. The I-bit in the DATA Chunk Header The following Figure 1 shows the extended DATA chunk. 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 0 | Res |I|U|B|E| Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TSN | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Stream Identifier | Stream Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Payload Protocol Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ \ / User Data / \ \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1 The only difference between the DATA chunk in Figure 1 and the DATA chunk defined in [RFC4960] is the addition of the I-bit in the flags field of the chunk header. Tuexen, et al. Expires January 6, 2009 [Page 3] Internet-Draft SACK-IMMEDIATELY July 2008 4. Procedures 4.1. Sender Side Considerations Whenever the sender of a DATA chunk can benefit from the corresponding SACK chunk being sent back without delay, the sender MAY set the I-bit in the DATA chunk header. Reasons for setting the I-bit include o The sender has not enough queued user data to send the remaining DATA chunks due to the Nagle algorithm. o The sending of a DATA chunk fills the congestion or receiver window. o The sender is in the SHUTDOWN-PENDING state. o The sender has reduced its RTO.Min such that a retransmission timeout will occur if the receiver would delay its SACK. 4.2. Receiver Side Considerations On reception of an SCTP packet containing a DATA chunk with the I-bit set, the receiver SHOULD NOT delay the sending of the corresponding SACK chunk and SHOULD send it back immediately. 5. Interoperability Considerations According to [RFC4960] a receiver of a DATA chunk with the I-bit set should ignore this bit when it does not support the extension described in this document. Since the sender of the DATA chunk is able to handle this case, there is no requirement for negotiating the feature described in this document. 6. IANA Considerations There are no actions required from IANA. 7. Security Considerations This document does not add any additional security considerations in addition to the ones given in [RFC4960]. Tuexen, et al. Expires January 6, 2009 [Page 4] Internet-Draft SACK-IMMEDIATELY July 2008 8. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC 4960, September 2007. Authors' Addresses Michael Tuexen Muenster Univ. of Applied Sciences Stegerwaldstr. 39 48565 Steinfurt Germany Email: tuexen@fh-muenster.de Irene Ruengeler Muenster Univ. of Applied Sciences Stegerwaldstr. 39 48565 Steinfurt Germany Email: i.ruengeler@fh-muenster.de Randall R. Stewart The Resource Group 1700 Pennsylvania Ave NW Suite 56 Washington, DC 20006 USA Phone: Email: randall.stewart@trgworld.com Tuexen, et al. Expires January 6, 2009 [Page 5] Internet-Draft SACK-IMMEDIATELY July 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 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The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Tuexen, et al. Expires January 6, 2009 [Page 6]