mail voor linux mailinglist

mail voor linux mailinglist

[Johannes Deleu]

Hi,

for a project, we're interested in using DCCP. As such, I did some 
performance measurements with the latest version of the DCCP 
implementation. To my opinion, they are not really what I expected. 
Could you give some ideas or maybe some information about the current 
status of the implementation (e.g. is packet loss detection planned for 
implementation, when ?) ?

Results of similar tests are also interesting to see if they compare.
For the tests, I used an impairment node (based on linux, which 
introduced some packet loss).

Measurements where performed with the patched iperf on linux-2.6.16.20 
and I came to the following table:

                    TCP                 DCCP-CCID3 (Send/Recv)
No drop       94 Mbps          93.3 Mbps      93.2 Mbps
Drop 1%      83.4 Mbps       93.3 Mbps      92.3 Mbps
Drop 5%      16.6 Mbps       93.3 Mbps      88.6 Mbps
Drop 10%    3.25 Mbps       93.3 Mbps      83.9 Mbps

The transmitter does not detect the packet loss and doesnt slow down, 
instead it keeps sending <CCID option 192 4294967295>.
As CCID3 is TFRC, I expected similar results for TCP and DCCP-CCID3.

When i tried out linux-2.6.17.1 (no packet drop) the receiver seems to 
stop sending feedback packets after a while and the transmitter slows 
down. The receiving process doesnt receive any data (recv doesnt return).

[  3] local 10.0.1.3 port 3743 connected with 10.0.1.1 port 5001
[  3]  0.0- 1.0 sec  11.0 MBytes  92.5 Mbits/sec
[  3]  1.0- 2.0 sec  10.9 MBytes  91.6 Mbits/sec
[  3]  2.0- 3.0 sec  10.9 MBytes  91.6 Mbits/sec
[  3]  3.0- 4.0 sec  10.9 MBytes  91.6 Mbits/sec
[  3]  4.0- 5.0 sec  10.9 MBytes  91.6 Mbits/sec
[  3]  5.0- 6.0 sec  10.9 MBytes  91.6 Mbits/sec
[  3]  6.0- 7.0 sec  6.86 MBytes  57.5 Mbits/sec
[  3]  7.0- 8.0 sec    194 KBytes  1.59 Mbits/sec
[  3]  8.0- 9.0 sec    100 KBytes    819 Kbits/sec
[  3]  9.0-10.0 sec    100 KBytes    819 Kbits/sec
[  3] 10.0-11.0 sec    100 KBytes    819 Kbits/sec
[  3] 11.0-12.0 sec    100 KBytes    819 Kbits/sec
[  3] 12.0-13.0 sec    100 KBytes    819 Kbits/sec

best regards,
Johannes

Re: mail voor linux mailinglist

[Ian McDonald]

On 6/23/06, Johannes Deleu <Johannes.Deleu@intec.ugent.be> wrote:
>
> Hi,
>
> for a project, we're interested in using DCCP. As such, I did some
> performance measurements with the latest version of the DCCP
> implementation. To my opinion, they are not really what I expected.
> Could you give some ideas or maybe some information about the current
> status of the implementation (e.g. is packet loss detection planned for
> implementation, when ?) ?

Packet loss has been implemented and is working for me. What is your
test environment? I am using netem on a router between two boxes.
>
> Results of similar tests are also interesting to see if they compare.
> For the tests, I used an impairment node (based on linux, which
> introduced some packet loss).
>
> Measurements where performed with the patched iperf on linux-2.6.16.20
> and I came to the following table:
>
>                     TCP                 DCCP-CCID3 (Send/Recv)
> No drop       94 Mbps          93.3 Mbps      93.2 Mbps
> Drop 1%      83.4 Mbps       93.3 Mbps      92.3 Mbps
> Drop 5%      16.6 Mbps       93.3 Mbps      88.6 Mbps
> Drop 10%    3.25 Mbps       93.3 Mbps      83.9 Mbps
>
> The transmitter does not detect the packet loss and doesnt slow down,
> instead it keeps sending <CCID option 192 4294967295>.
> As CCID3 is TFRC, I expected similar results for TCP and DCCP-CCID3.
>
> When i tried out linux-2.6.17.1 (no packet drop) the receiver seems to
> stop sending feedback packets after a while and the transmitter slows
> down. The receiving process doesnt receive any data (recv doesnt return).
>
> [  3] local 10.0.1.3 port 3743 connected with 10.0.1.1 port 5001
> [  3]  0.0- 1.0 sec  11.0 MBytes  92.5 Mbits/sec
> [  3]  1.0- 2.0 sec  10.9 MBytes  91.6 Mbits/sec
> [  3]  2.0- 3.0 sec  10.9 MBytes  91.6 Mbits/sec
> [  3]  3.0- 4.0 sec  10.9 MBytes  91.6 Mbits/sec
> [  3]  4.0- 5.0 sec  10.9 MBytes  91.6 Mbits/sec
> [  3]  5.0- 6.0 sec  10.9 MBytes  91.6 Mbits/sec
> [  3]  6.0- 7.0 sec  6.86 MBytes  57.5 Mbits/sec
> [  3]  7.0- 8.0 sec    194 KBytes  1.59 Mbits/sec
> [  3]  8.0- 9.0 sec    100 KBytes    819 Kbits/sec
> [  3]  9.0-10.0 sec    100 KBytes    819 Kbits/sec
> [  3] 10.0-11.0 sec    100 KBytes    819 Kbits/sec
> [  3] 11.0-12.0 sec    100 KBytes    819 Kbits/sec
> [  3] 12.0-13.0 sec    100 KBytes    819 Kbits/sec
>
There are a few issues still with DCCP at the moment (which is why it
is marked experimental). Keep supplying us data/info and we will see
what we will do. Nobody is working fulltime on this code so it can
take a while to fix - feel free to help though!

One note - when using CCID3 have you turned off ackvecs via the sysctl
as that is really for CCID2... It's probably something we should do in
the code actually.

Ian
-- 
Ian McDonald
Web: http://wand.net.nz/~iam4
Blog: http://imcdnzl.blogspot.com
WAND Network Research Group
Department of Computer Science
University of Waikato
New Zealand