Herve,
<snip>
> 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 !?!
I don't have access to an HPUX box here, but the problem you are
experiencing may be related to the the default *maximum* socket buffer
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
size for your boxes. This setting is the system-wide default value, and
will impose an upper-limit on whatever you do with a setsockopt(). So,
socket_buffer_size = min(setsockopt(), maximum socket buffer size)
I think you can change the maximum socket buffer parameter for the
system using "nettune" (or something like that);
This is a common problem when trying to make use of RFC-1323 window-scaling,
but it looks like ttcp would complain about buffer space not being
available if this were biting you :o(
For what it is worth, the folks at the Pittsburgh Supercomputing Center
have a good web page that covers this kind of stuff for many different
Operating Systems; I think the link is off of:
http://www.psc.edu/networking/
Just in case you haven't done this already, you might want to check the
following:
- Run tcpdump (or the like) to watch the options offered with the
connection's SYN segments. If window-scaling is offered by default,
you will see the option with all SYNs, even if the scale factor
offered is 0 (window size =< 64KB)
- If you don't see the option being offered at all, chances are that
the RFC-1323 options are disabled; You can probably use "nettune"
to change this too; I don't know if RFC-1323 extensions are enabled
by default in HPUX 10
Best of luck,
Eric
This archive was generated by hypermail 2b29 : Mon Feb 14 2000 - 16:14:29 EST