HEADS UP: SACK committed to HEAD
tjr at freebsd.org
Thu Jun 24 17:12:21 PDT 2004
On Fri, Jun 25, 2004 at 09:16:38AM +0930, Wilkinson, Alex wrote:
> erm .... what is SACK ? I'm assuming ACK is 'acknowledgment ?
> Quick summary anyone ?
>From RFC 2018:
TCP may experience poor performance when multiple packets are lost
from one window of data. With the limited information available
from cumulative acknowledgments, a TCP sender can only learn about a
single lost packet per round trip time. An aggressive sender could
choose to retransmit packets early, but such retransmitted segments
may have already been successfully received.
A Selective Acknowledgment (SACK) mechanism, combined with a
selective repeat retransmission policy, can help to overcome these
limitations. The receiving TCP sends back SACK packets to the sender
informing the sender of data that has been received. The sender can
then retransmit only the missing data segments.
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