Re: Why is my gigabit ethernet so slow?

[Steven Bellovin <smb%cs.columbia.edu@localhost>]

On Jan 27, 2010, at 7:44 AM, Martti Kuparinen wrote:

> Martti Kuparinen wrote:
> 
>> As a reminder, the setup is like this:
>> S (Ubuntu 9.10) <--> X (NetBSD 5.99.24) <--> R (NetBSD 5.99.24)
> 
> I found http://proj.sunet.se/E2E/tcptune.html and played a little with the 
> receiver (NetBSD 5.99.24), below 3 runs with both settings. The conclusion is 
> that I'm happy now as I'm able to route 850+ Mbps through my router...
> 
> Step 1
> ------
> (Rebuilt kernel with "options NMBCLUSTERS=16384")
> sysctl -w kern.sbmax=8388608
> sysctl -w net.inet.tcp.sendspace=3217968
> sysctl -w net.inet.tcp.recvspace=3217968
> sysctl -w net.inet.tcp.init_win=8
> 
> TCP
> ttcp-t: 10737418240 bytes in 96.02 real seconds = 853.20 Mbit/sec +++
> ttcp-t: 10737418240 bytes in 96.55 real seconds = 848.45 Mbit/sec +++
> ttcp-t: 10737418240 bytes in 97.14 real seconds = 843.29 Mbit/sec +++
> 
> UDP
> ttcp-t: 10737418240 bytes in 93.84 real seconds = 872.95 Mbit/sec +++
> ttcp-t: 10737418240 bytes in 93.84 real seconds = 872.94 Mbit/sec +++
> ttcp-t: 10737418240 bytes in 93.84 real seconds = 872.96 Mbit/sec +++
> 
> Step 2
> ------
> 
> (Reboot and activate all the settings from step 1 and the following two)
> sysctl -w net.inet.tcp.sendbuf_max=16777216
> sysctl -w net.inet.tcp.recvbuf_max=16777216
> 
> TCP
> ttcp-t: 10737418240 bytes in 95.92 real seconds = 854.04 Mbit/sec +++
> ttcp-t: 10737418240 bytes in 96.80 real seconds = 846.26 Mbit/sec +++
> ttcp-t: 10737418240 bytes in 96.54 real seconds = 848.52 Mbit/sec +++
> 
> UDP
> ttcp-t: 10737418240 bytes in 93.85 real seconds = 872.89 Mbit/sec +++
> ttcp-t: 10737418240 bytes in 93.83 real seconds = 873.03 Mbit/sec +++
> ttcp-t: 10737418240 bytes in 93.87 real seconds = 872.72 Mbit/sec +++
> 
> 
Especially with udp, look at the receiver's numbers, not the transmitter's.


                --Steve Bellovin, http://www.cs.columbia.edu/~smb