On Fri, 22 Aug 1997, Herve Degrand wrote:
>
> Hello,
>
> I am a french student having a placement in BT. A part of my
> project is to analyse performances of TCP over satellite connections.
> At the present time, we are notably interested in windows scaling
> options, how it increases throughput. The problem is that I don't
> manage to trigger tcp windows scaling. I am working within HPUX 10
> which is supposed to support RFC 1323 (windows scale). I have tried
> with programms like netperf or ttcp to setup some big buffer size at
> both end points, in order to enforce TCP end-points to use and
> announce a shift count factor (in the SYN packet). But it doesn't
> work. Every light on this subject would be definitvely welcome !?!
>
> Regards,
>
> herve
>
> _______________________________
>
> Herve DEGRAND
> British Telecom Labs
> B29-129, Martlesham Heath
> IPSWICH, IP5 3RE ENGLAND
> Phone:(01473)-640880
> International: 44+1473640880
> _______________________________
>
If the TCP implementation in the OS kernels in both end hosts supports
scaling windows according to RFC 1323, then by running lets say ttcp with
the correct parameters, it should be working just fine. Be sure you are
using the -b parameter in ttcp, in both ends, which specifies the buffer
size (i.e the TCP window size) with which you want to run the experiment.
That parameter passes to the operating system kernel via the "setsockopt"
system level function the new buffer size, and thus the defualt
value(usually 32KB in most OS) will not be used.
e.g:
transmitter host:
----------------------
%ttcp -t -b1048576 -l65536 -n1024 xxx.xxx.xxx.xxx
receiver host:
----------------
%ttcp -r -b1048576 -l65536 -n1024
As soon the connection is estsablished (via sockets) between the two
hosts, 1024 buffers of 64KB blocks will be transffered using scaling
windows of 1MB.
(xxx.xxx.xxx.xxx is the IP of the receiver).
Personally I would recommend the use of another Network Performance
Evaluation Tool, developed here in the University of Kansas, called
Netspec. Information on Netspec can be found at:
http://www.ittc.ukans.edu/netspec
Pambos
////////////////////////////////////////////////////////////////
Charalambous Charalambos (Pambos) //
Department of Electrical and Computer Engineering //
Research Assistant - The University of Kansas //
E-mail: [email protected] // [email protected] //
URL: http://www.eecs.ukans.edu/~pambos/cyprus //
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