The timing of this is coincidental. I've been helping to troubleshoot a similar problem at work for days. Let's say we have three servers, A, B and C. We transfer files between them and here is what we see:
A to B: Fast (around 18 MB/s) B to A: Slow (around 1 MB/s) A to C: Slow (around 1MB/s) C to A: Fast (around 18MB/s) In our case, Server A is fast when sending to B but not when sending to C. C can send at a high speed when sending back to A, though. We've checked everything we can think of. The paths aren't the same. One path goes through a firewall, another path goes through GRE tunnels. There are no TCP retransmits and we've verified that MTU isn't the problem. The firewall can't be the problem because it's only in the path of one set of transfers. All the TCP settings we've checked on the servers seem to be the same, although I'm not a server guy. Someone else has been checking those. The endpoints are on 1-gig links but it's 10-gig the whole way between them. There is about 50ms round-trip latency in all cases. I have no idea what could account for this behavior. On Sun, Apr 29, 2012 at 5:41 AM, <[email protected]> wrote: > I have seen this before, it's called bandwidth delay product and is linked to > window size, let us know the tcp results after you have adjusted. > > > Sent from my iPad > > On 29 Apr 2012, at 10:22, CiscoNSP_list CiscoNSP_list > <[email protected]> wrote: > >> >> >> >>> >>> Did you run your iperf tests also with UDP? (The numbers don't look >>> like it.) >>> >>> With TCP you won't see many drops on your switches, it will adjust - and >>> you will see less throughput. >>> >>> With iperf available at all three sites I would run tests with UDP streams. >>> This won't find the maximum bandwith automatically, you have to set a >>> bandwidth for testing and see if you have any packet loss. >>> >>> Keep in mind that your carrier might police on ethernet bandwidth, >>> iperf measures IP throuput. >> >> Thanks Klaus - No, did not test with udp...here it is: >> (With 100M had too many drops - 80M was the best:)[ 3] local xxx.xxx.73.54 >> port 45790 connected with xxx.xxx.65.2 port 5001[ ID] Interval >> Transfer Bandwidth[ 3] 0.0-10.0 sec 95.4 MBytes 80.0 Mbits/sec[ 3] >> Sent 68029 datagrams[ 3] Server Report:[ 3] 0.0-10.0 sec 95.4 MBytes >> 80.0 Mbits/sec 0.044 ms 1/68028 (0.0015%)[ 3] 0.0-10.0 sec 1 >> datagrams received out-of-order >> So to be able to see similar performance with tcp, I will need to adjust tcp >> window correct? >> >> >> _______________________________________________ >> cisco-nsp mailing list [email protected] >> https://puck.nether.net/mailman/listinfo/cisco-nsp >> archive at http://puck.nether.net/pipermail/cisco-nsp/ > > _______________________________________________ > cisco-nsp mailing list [email protected] > https://puck.nether.net/mailman/listinfo/cisco-nsp > archive at http://puck.nether.net/pipermail/cisco-nsp/ _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
