cisconsp_list at hotmail
Apr 29, 2012, 12:34 AM
Network performance question - TCP Window issue?
(Apologies if this is too off-topic for the cisco list)
Have 3 POPs A,B+C (A connected to B via 200Mb Eth, B connected to C via 250Mb Eth), all POPs are 7200's with 2960's and 3560's
A -> B, 2 - 3 m/sec (No packet loss, minimal jitter)
B -> C, 12 - 13 m/sec (No packet loss, minimal jitter)
Performing wget or iperf I see the following (Have linux servers at each POP)
Pulling file from B->A (A's linux server is on 10/100 port) I get 9.59M/s (So basically 100Mbit)
Pulling file from C->B I get 8.30M/s, but it does fluctuate up+down considerably
Pulling file from C->A I get a flatline at 2.16M/s (Multiple sessions and all attain this speed, but no faster and doesnt fluctuate)
Im not seeing any excessive errors/drops nor any duplex issues on any of the switches - Is TCP Window size the cause of the huge speed difference I see from C->B vs C->A, even though the latency difference between the 2 is minimal?(i.e. 3m/sec?) or does the extra hop cause the issue?
thanks in advance for any advice.
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