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New Member

TCP transfer issues over WAN link

I have a strange issue thats been a thorn in my side for the over a month now.

I can do a single stream tcp transfer over a 100mb link and I can get 50mbps in one direction but only 4mbps in the other direction.

The setup is as follows

dell with 1gig nic ->  cisco 3560 ->  100mbps layer 2 circuit 60ms latency -> cisco 3560x -> dell with 1 gig nic                                                                                                                        

i do an iperf -c -d  from and my results are

[  4]  0.0-10.0 sec  93.2 MBytes  77.9 Mbits/sec

[  5]  0.0-10.3 sec  3.02 MBytes  2.47 Mbits/sec

However if I knock down both dells to 100mbps (speed 100, duplex full) and I hard code the interfaces to 100meg full on each server

The very same test yields

[  5]  0.0-10.0 sec  50.4 MBytes  42.2 Mbits/sec

[  4]  0.0-10.0 sec  59.4 MBytes  49.6 Mbits/sec

which is perfect.  So what the heck is going on?  Why would going from gig to 100mb and back to gig result in such poor performance?  Is there any config changes I can do to make this work?  I need my servers at 1gig.

Everyone's tags (6)
New Member

TCP transfer issues over WAN link

problem is actually now resolved.  I just had to restrict the bandwidth on the uplink interfaces with srr-queue bandwidth limit 10