[c-nsp] Centos upload speed slower on 1000m than 100m over WAN links

[Arie Vayner (avayner)]

Paul,

I am not really aware of the fine details on the CentOS thingie, but can
you describe how the upstream network connection of that server looks
like? What lies beyond the NIC in the next few network hops.

Thanks
Arie

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Paul
Sent: Sunday, June 27, 2010 09:04
To: cisco-nsp at puck.nether.net
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
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paul at gtcomm.net
http://www.gtcomm.net 

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