On Thu, Jun 19, 2008 at 03:07:27PM -0700, Christopher Hunt wrote:
> I am familiar with TCP's concept of Slow Start, but my understanding
> is that it is the RWIN that is slow to start. The packet does show the
> first packet as 24 Byte payload, but even then the client RWIN is 5888
> (scaled x7) (CentOS running 2.6.18 kernel). The "server" is XP Pro
> running an RWIN 65535 with scaling disabled. As far as I can tell, TCP
> slow start is not happenning. What other signs of Slow Start should i
> be looking for?
every second (+/- .1s) the drops occur and SACK kicks in:
23:05:46.809550 IP 192.168.10.2.33538 > 10.180.55.211.commplex-link: .
115865:117313(1448) ack 1 win 46 <nop,nop,timestamp 754051101 746671>
23:05:46.810977 IP 10.180.55.211.commplex-link > 192.168.10.2.33538: . ack
117313 win 65535 <nop,nop,timestamp 746671 754051101>
23:05:46.810997 IP 192.168.10.2.33538 > 10.180.55.211.commplex-link: .
117313:121657(4344) ack 1 win 46 <nop,nop,timestamp 754051103 746671>
ack 120209 begins, backlog to 126001 occurs:
23:05:46.812489 IP 10.180.55.211.commplex-link > 192.168.10.2.33538: . ack
120209 win 65535 <nop,nop,timestamp 746671 754051103>
23:05:46.812508 IP 192.168.10.2.33538 > 10.180.55.211.commplex-link: .
121657:124553(2896) ack 1 win 46 <nop,nop,timestamp 754051104 746671>
SACK kicks in:
23:05:46.813864 IP 10.180.55.211.commplex-link > 192.168.10.2.33538: . ack
120209 win 65535 <nop,nop,timestamp 746671 754051103,nop,nop,sack 1
{121657:123105}>
23:05:46.813883 IP 192.168.10.2.33538 > 10.180.55.211.commplex-link: .
124553:126001(1448) ack 1 win 46 <nop,nop,timestamp 754051105 746671>
23:05:46.814051 IP 10.180.55.211.commplex-link > 192.168.10.2.33538: . ack
120209 win 65535 <nop,nop,timestamp 746671 754051103,nop,nop,sack 1
{121657:124553}>
23:05:46.814070 IP 192.168.10.2.33538 > 10.180.55.211.commplex-link: .
126001:127449(1448) ack 1 win 46 <nop,nop,timestamp 754051106 746671>
23:05:46.815196 IP 10.180.55.211.commplex-link > 192.168.10.2.33538: . ack
120209 win 65535 <nop,nop,timestamp 746671 754051103,nop,nop,sack 1
{121657:126001}>
ack of last sack packet:
23:05:46.815214 IP 192.168.10.2.33538 > 10.180.55.211.commplex-link: .
120209:121657(1448) ack 1 win 46 <nop,nop,timestamp 754051107 746671>
.4 second delay, retransmit of ack of last sack packet:
23:05:47.237107 IP 192.168.10.2.33538 > 10.180.55.211.commplex-link: .
120209:121657(1448) ack 1 win 46 <nop,nop,timestamp 754051529 746671>
acks 120209-126001 finally occur, 10.180.55.211 moves on, .45 seconds later
23:05:47.238740 IP 10.180.55.211.commplex-link > 192.168.10.2.33538: . ack
126001 win 65535 <nop,nop,timestamp 746675 754051529>
23:05:47.238771 IP 192.168.10.2.33538 > 10.180.55.211.commplex-link: .
126001:127449(1448) ack 1 win 46 <nop,nop,timestamp 754051530 746675>
this pattern repeats frequently. sometimes with a retransmit, sometimes
without, always taking .3-.5 seconds or so. hence, the crap performance.
-- bill
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