Joe, this is exactly the phenomena I was referring to. It can be controlled with applying shaping on platforms that can support this kind of QOS policy (requires large buffers). Usually available on WAN routers, specific switches or requires specific modules on some other switches.
Arie -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Joe Loiacono Sent: Monday, June 28, 2010 17:11 To: Paul Cc: [email protected]; [email protected] Subject: Re: [c-nsp] Centos upload speed slower on 1000m than 100m over WANlinks 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. Joe From: Paul <[email protected]> To: [email protected] 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 [email protected] http://www.gtcomm.net _______________________________________________ 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/
