[e2e] query reg improving TCP performane
query.cdac at gmail.com
Thu Jul 5 07:39:02 PDT 2007
I was doing some Bandwidth measurement test on a 100 mbs link with a RTT
of about 70ms.
Based on that, I calculated the BDP as follows.
BDP = Bandwidth * RTT
= 13107200 bytes * .07 secs
= 896 Kbytes
= 900 Kbyes (approx)
= 921600 bytes
After that I adjusted the TCP window size as follows:
/proc/sys/net/ipv4/tcp_rmem 4096 87380 921600
/proc/sys/net/ipv4/tcp_wmem 4096 87380 921600
These adjustmenst I had done on a Linux host with 2.6.15 kernel. The
control algorithm , it is using BIC
The same window adjustments I had performed on the other hand on a Linux
with kernel 2.6.9 . It is also using BIC for congestion control.
The Bandwidth Performnce test I am doing using iperf , a highly popular
domain tool for measuring TCP & UDP Bandwidth Performance .
With the default Linux 2.6 TCP window settings , I was getting a
nearly 10mbs which is very low for a 100 mbs link.
So , I performed the above TCP adjustmets and I found the throughput to
55 mbs which is a significant improvement . But that is not fully
utilsing the link
as it is a dedicated link and there was no other traffic.
This , I proved with the next experiment where I reached a link
little more than 95 mbs . That is very much O.K for a 100mbs link.
I did the following adjustments. I increased the above calculated BDP by
half of the value . The TCP settings now look like this.
/proc/sys/net/ipv4/tcp_rmem 4096 87380 175636
/proc/sys/net/ipv4/tcp_wmem 4096 87380 175636
After these settings , I find the link utilisation to be nearly 95 mbs.
According to many papers that I read , I found that the BDP should be
to the product of Bandwidth * RTT .
I had done that , but the link utilisation is only 50%. But when I
to a much higher value , the link utilisation is nearly around 95 %.
I am confused regarding my findings.Please clarify me so that I can
the experiment correctly.
With Thanks in Advance
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