Hi,
I'm sure you'll get this from more than one of us, but :o)
You didn't mention a few items that might diagnose the problem:
(0) What was the length of the transfers? Short transfers will have
their performance severly impacted by slow-start, although
congestion avoidance will not help much either :o(
(1) Do you have the size of the buffers allocated at both sides of
the connection?
These would either be the default socket buffer sizes provided
by the operating system (32 KB for Linux 2.0.x), but ??? for OS/2
(maybe 8KB?)
(2) What was the MSS being used? I'm guessing that it was something
536 bytes. This hurts in slow-start. I'm guessing that OS/2
doesn't do Path-MTU discovery, but Linux does. How old are the
routers - old routers aren't terribly helpful in speeding up the
Path-MTU discovery cycle.
(2) The end-to-end delay across the network path. I'm guessing this
is a geostationary satellite - but pinging one end from the other
would provide a good estimate of this value.
(3) Does the ftp client override the default socket buffer values?
If so, is this tunable - and do we know what the new values are?
(4) Finally, is it possible that you are experiencing corruption over
the satellite link (or anywhere else)?
Some of this information might be tough to dig out, unfortunately that's
part of the fuzziness of dealing with satellite links. :o(
I'm attempting to push out an I-D by this afternoon that (I hope)
will explain these things... It'll be a bit rough but it'll get
smoothed out shortly.
Good Luck!
Eric
On Fri, 13
Mar 1998, Dr.
Bettina Pieper wrote:
> Hello,
>
> I am still struggling with my problem to have an efficient data-rate for
> ftp over a transparent 384 kb/s satellite link:
>
> The configuration is as follows:
>
> PC1 - Router 1 - Sat-Modem 1 <--- EUTELSAT ---> Sat-Modem 2 - Router 2
> - PC2
>
> PC1 and 2 with Ethernet-Interface (10 Mb/s)
> Router1 3COM, NetBuilderII with RS449-Interface; Software Version
> 7.2
> Router2 3COM, NetBuilder Remote Office 227 with RS449-Interface;
> Software Version 7.2
>
> Some tests:
> Test configuration 1:
> PCs running OS/2 2.11; IBM TCP/IP version 2; PPP on the Router
> result: ftp of the same 350 kB-File in 96 s, 6.5 s, 9.6s, 140 s, ...
> that means no constant rate
>
> Test configuration 2:
> PCs running with Linux-Boot-Disks (Kernel vers. 2.0.?); PPP on the
> Router
> one test with TTCP with 1024 byte Packets: 23 kB/s = 50% of the max data
> rate
> (I will keep on testing with the Linux config.)
>
> Any idea for "the best" configuration of the Routers - maybe as a
> Bridge, compression y/n and which one (Per Packet or History), etc. and
> maybe another ftp-Software.
>
> I would appreciate help very much.
>
> Bettina Pieper
>
> --
> ----------------------------------------------------------------
> University of Ulm, DR-1
> Dr. Bettina Pieper
> E.C./R&D Management in the President's Office
> D-89069 Ulm
>
> phone: +49-731-50-22010/2011
> fax: +49-731-50-22016
> e-mail: [email protected]
> http://www.uni-ulm.de
>
>
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