Bigger is not better for slow networks. For a link speed of 4kbps you will
need to use much smaller MTU sizes since the transmission time for a packet
gets too long otherwise. It will also depend upon what the latency is in the
link because the total transmission time for a packet is a function of the
size and delay. For a typical GEO link, I would expect that you have
anywhere up to 600ms depending upon what kind of FEC and interleaving is
done on the link. I have found for Inmarsat-M/Mini-M type links (2.4 kbps)
that an MTU size of 500 works well. You also need to adjust the initial RTO
value larger (the default is 3 secs, try 5 secs). If you don't do this, you
will suffer a lot of timeouts and retransmissions. I'm not that familiar
with the protocol Citrix uses, but with only 4kbps of bandwidth, you also
don't want to run multiple simultaneous connections across your link as one
connection will probably saturate the link.
-Greg
LCDR Gregory W. Johnson
Ass't Prof. Electrical Engineering
USCG Academy
New London CT
860-444-8683
-----Original Message-----
From: Julien Godard [mailto:[email protected]]
Sent: Tuesday, February 15, 2000 4:59 AM
To: 'Testasecca, Mariano'
Cc: '[email protected]'
Subject: RE: Setting the appropiate MTU
for performance, the bigger the better !
But it may depend also on your network because you may want to avoid
fragmentation.
You can test your MTU with some free tools such as easyMTU
http://members.tripod.com/~EasyMTU/ <http://members.tripod.com/~EasyMTU/>
For example if you use ethernet link, the MTU is 1500, leading to 1448 bytes
of data in each segment (20 IP + 20 TCP + 12 TCP timestamp option + 1448
data). If your router support this size without fragmentation, it's fine !
-----Original Message-----
From: Testasecca, Mariano [SMTP:[email protected]]
Sent: Monday, February 14, 2000 7:49 PM
To: '[email protected]'
Subject: Setting the appropiate MTU
What MTU value would be appropiate for Windows 95/98 terminals
working as a
Windows NT 4.0 running Citrix MetaFrame under
a satellite link of a VSAT that provides 4kbps of bandwidth?
Thanks to all.
Mariano Testasecca
SIEMENS S.A.
Divisi�n Electromedicina
Servicios de Salud - SHS
Bolivar 177 1� Piso
*+54-11-4340-8400 int. 2796
* mailto:[email protected]
<mailto:[email protected]>
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