SACK-IMMEDIATELY Extension for the Stream Control Transmission Protocol
draft-tuexen-tsvwg-sctp-sack-immediately-08

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Network Working Group                                          M. Tuexen
Internet-Draft                                              I. Ruengeler
Intended status: Standards Track        Muenster Univ. of Appl. Sciences
Expires: May 1, 2012                                          R. Stewart
                                                          Adara Networks
                                                        October 29, 2011

SACK-IMMEDIATELY Extension for the Stream Control Transmission Protocol
            draft-tuexen-tsvwg-sctp-sack-immediately-08.txt

Abstract

   This document defines a method for the sender of a DATA chunk to
   indicate that the corresponding SACK chunk should be sent back
   immediately and not be delayed.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on May 1, 2012.

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   described in the Simplified BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  The I-bit in the DATA Chunk Header  . . . . . . . . . . . . . . 4
   4.  Procedures  . . . . . . . . . . . . . . . . . . . . . . . . . . 4
     4.1.  Sender Side Considerations  . . . . . . . . . . . . . . . . 4
     4.2.  Receiver Side Considerations  . . . . . . . . . . . . . . . 5
   5.  Interoperability Considerations . . . . . . . . . . . . . . . . 5
   6.  Socket API Considerations . . . . . . . . . . . . . . . . . . . 5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   8.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     10.1. Normative References  . . . . . . . . . . . . . . . . . . . 6
     10.2. Informative References  . . . . . . . . . . . . . . . . . . 6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 6

Tuexen, et al.             Expires May 1, 2012                  [Page 2]
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1.  Introduction

   According to [RFC4960] the receiver of a DATA chunk should use
   delayed SACKs.  This delaying is completely controlled by the
   receiver of the DATA chunk.

   In specific situations the delaying of SACKs results in reduced
   performance of the protocol.  If such a situation can be detected by
   the receiver, the corresponding SACK can be sent immediately.  For
   example, [RFC4960] recommends the immediate sending if the receiver
   has detected message loss or message duplication.  However, if the
   situation can only be detected by the sender of the DATA chunk,
   [RFC4960] provides no method of avoiding the delaying of the SACK.
   Thus the protocol performance might be reduced.

   This document overcomes this limitation and describes a simple
   extension of the SCTP DATA chunk by defining a new flag, the I-bit.
   The sender of a DATA chunk indicates by setting this bit that the
   corresponding SACK chunk should not be delayed.

   Upper layers of SCTP using the socket API as defined in
   [I-D.ietf-tsvwg-sctpsocket] may subscribe to the
   SCTP_SENDER_DRY_EVENT for getting a notification as soon as no user
   data is outstanding anymore.  To avoid an unnecessary delay while
   waiting for such an event, the application might set the I-Bit on the
   last DATA chunk sent before waiting for the event.  This enabling is
   possible using the extension of the socket API described in