draft-ietf-tcpm-3517bis-00.txt   draft-ietf-tcpm-3517bis-01.txt 
Internet Engineering Task Force E. Blanton Internet Engineering Task Force E. Blanton
INTERNET-DRAFT Purdue University INTERNET-DRAFT Purdue University
draft-ietf-tcpm-3517bis-00.txt M. Allman draft-ietf-tcpm-3517bis-01.txt M. Allman
ICSI ICSI
L. Wang L. Wang
Juniper Networks Juniper Networks
I. Jarvinen I. Jarvinen
M. Kojo M. Kojo
University of Helsinki University of Helsinki
Y. Nishida Y. Nishida
WIDE Project WIDE Project
January 12, 2012 January 26, 2012
A Conservative Selective Acknowledgment (SACK)-based A Conservative Selective Acknowledgment (SACK)-based
Loss Recovery Algorithm for TCP Loss Recovery Algorithm for TCP
Status of this Memo Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with This Internet-Draft is submitted to IETF in full conformance with
the provisions of BCP 78 and BCP 79. the provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
skipping to change at page 5, line 53 skipping to change at page 5, line 53
window allows, the sequence range of one segment of up to SMSS window allows, the sequence range of one segment of up to SMSS
octets of previously unsent data starting with sequence number octets of previously unsent data starting with sequence number
HighData+1 MUST be returned. HighData+1 MUST be returned.
(3) If the conditions for rules (1) and (2) fail, but there exists (3) If the conditions for rules (1) and (2) fail, but there exists
an unSACKed sequence number 'S3' that meets the criteria for an unSACKed sequence number 'S3' that meets the criteria for
detecting loss given in steps (1.a) and (1.b) above detecting loss given in steps (1.a) and (1.b) above
(specifically excluding step (1.c)) then one segment of up to (specifically excluding step (1.c)) then one segment of up to
SMSS octets starting with S3 SHOULD be returned. SMSS octets starting with S3 SHOULD be returned.
We believe that the triggering of rule (3) will be rare and
that the implications are likely limited to corner cases
relative to the entire recovery algorithm. Therefore we leave
the decision of whether or not to use rule (3) to
implementors.
(4) If the conditions for (1), (2), and (3) fail, but there (4) If the conditions for (1), (2), and (3) fail, but there
exists outstanding unSACKed data, we provide the exists outstanding unSACKed data, we provide the
opportunity for a single "rescue" retransmission per entry opportunity for a single "rescue" retransmission per entry
into loss recovery. If HighACK is greater than RescueRxt into loss recovery. If HighACK is greater than RescueRxt
(or RescueRxt is undefined), then one segment of up to (or RescueRxt is undefined), then one segment of up to
SMSS octets which MUST include the highest outstanding SMSS octets which MUST include the highest outstanding
unSACKed sequence number SHOULD be returned, and RescueRxt unSACKed sequence number SHOULD be returned, and RescueRxt
set to RecoveryPoint. HighRxt MUST NOT be updated. set to RecoveryPoint. HighRxt MUST NOT be updated.
Note that rules (3) and (4) are a sort of retransmission "last Note that rules (3) and (4) are a sort of retransmission "last
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