On 6/28/10, Joe Loiacono <jloia...@csc.com> wrote: > OK I'm jumping in on this thread late as I just got back from some > vacation, don't know if this particluar observation has been discussed, > but ... > > We've seen this problem a lot when moving up to new local connection > speeds. The problem for us has been that unless the entire path can > support the new speed (e.g., 1G) switches down the path that connect to > slower speeds (e.g. 100M) will overflow and put your data transfer into > TCP slow-start recovery. As soon as the sending NIC is 'downgraded' (e.g., > back to 100 M) the overflows disappear, slow-start is avoided, and > performance improves. Bitterly ironic.
Have you checked to see if selective acks are enabled on both sides of the connection[s]? Lee > > Joe > > > > From: > Paul <p...@gtcomm.net> > To: > cisco-nsp@puck.nether.net > Date: > 06/27/2010 03:08 AM > Subject: > [c-nsp] Centos upload speed slower on 1000m than 100m over WAN links > > > > I'm not even sure this is the right forum but since we use mainly Cisco > equipment I'll give this a shot. :) > I have tried several centos based servers and compiled various kernels > and the results have been extremely weird. > 90% of the cases the remote hosts can download from a server at > 1-5megabytes per second, and most of these are over > the internet ranging from 30-200ms away. Local (1ms or less) is super > fast 100MB/s for example. > Ok that sounds normal since it's going over the internet, etc. But > here's the )(!...@*! part.. > If I set the port speed to 100 megabits full duplex on the switch and > server , the clients that get 1-5MB/s now get 11MB/s which is > approximately the limit of the 100mbit port. > Totally stumped here, tried different nics, servers, even 4 different > switches. Is a very interesting problem and I'm probing to see > if anyone else has encountered it. > So far the only OS i have tried is centos, but different versions and > kernels and hardware. > All the switches/routers are Cisco based, but I seriously doubt that has > anything to do with this. :P > > -- > GloboTech Communications > Phone: 1-514-907-0050 x 215 > Toll Free: 1-(888)-GTCOMM1 > Fax: 1-(514)-907-0750 > p...@gtcomm.net > http://www.gtcomm.net > > _______________________________________________ > cisco-nsp mailing list cisco-nsp@puck.nether.net > https://puck.nether.net/mailman/listinfo/cisco-nsp > archive at http://puck.nether.net/pipermail/cisco-nsp/ > > > _______________________________________________ > cisco-nsp mailing list cisco-nsp@puck.nether.net > https://puck.nether.net/mailman/listinfo/cisco-nsp > archive at http://puck.nether.net/pipermail/cisco-nsp/ > _______________________________________________ cisco-nsp mailing list cisco-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/