Subject: I-D Action: draft-natarajan-tsvwg-sctp-nrsack-08.txt

From: [email-masked]
Date: Mon, 15 Aug 2011 10:05:18 -0700

A New Internet-Draft is available from the on-line Internet-Drafts directories.

	Title           : Non-Renegable Selective Acknowledgements (NR-SACKs) for SCTP
	Author(s)       : Nasif Ekiz
                          Paul D. Amer
                          Preethi Natarajan
                          Randall R. Stewart
                          Janardhan Iyengar
	Filename        : draft-natarajan-tsvwg-sctp-nrsack-08.txt
	Pages           : 20
	Date            : 2011-08-15

   Stream Control Transmission Protocol (SCTP) [RFC4960] specifies
   Selective Acknowledgements (SACKs) to allow an SCTP data receiver to
   acknowledge DATA chunks which arrive out-of-order.  In SCTP, SACK
   information is advisory -- though SACKs notify a data sender about
   the reception of specific out-of-order data, the SCTP data receiver
   is permitted to later discard the data, a.k.a reneging.  Since
   delivery of a SACKed out-of-order DATA chunk is not guaranteed, a
   copy of this DATA chunk MUST be kept in the data sender&#39;s
   retransmission queue until this DATA chunk is cumulatively acked.

   By definition, data that has been delivered to the application is
   non-renegable by the SCTP data receiver.  (Recall that, in SCTP, out-
   of-order data can sometimes be delivered.)  Also, SCTP
   implementations can be configured such that the SCTP data receiver is
   not allowed to, and therefore, never reneges on out-of-order data.
   With SCTP&#39;s current SACK mechanism, non-renegable out-of-order data
   is selectively acked, and is (wrongly) deemed renegable by the SCTP
   data sender.

   This document specifies an extension to SCTP&#39;s acknowledgment
   mechanism called Non-Renegable Selective Acknowledgements (NR-SACKs.)
   NR-SACKs enable a data receiver to explicitly inform the data sender
   of non-renegable out-of-order data.  As opposed to renegable data, a
   data sender can consider non-renegable data as never requiring
   retransmission, and therefore can remove non-renegable data from the
   retransmission queue.

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