Subject: I-D Action:draft-natarajan-tsvwg-sctp-nrsack-06.txt

From: [email-masked]
Date: Wed, 18 Aug 2010 12:00:01 -0700 (PDT)

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

	Title           : Non-Renegable Selective Acknowledgements (NR-SACKs) for SCTP
	Author(s)       : N. Ekiz, et al.
	Filename        : draft-natarajan-tsvwg-sctp-nrsack-06.txt
	Pages           : 20
	Date            : 2010-08-18

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'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'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'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.

A URL for this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-natarajan-tsvwg-sctp-nrsack-06.txt

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