From: Jonathan V Hays (jhays@jtan.com)
Date: Tue Oct 21 2003 - 11:12:31 GMT-3
Paul,
Good question. I don't know the answer but I can give you an idea.
I suspect the tradeoff had more to do with CSMA/CD timing back in the
days when ethernet was run on a shared cable. If you were deciding on a
specification, you would pick a stable clock rate (for example, 10 Mbps,
just as a number pulled out of the air ;) which was dependent on the
level of technology at the time (1970s I think) and a maximum cable
length, and how long to listen on the cable before sending your frame
(CSMA/CD). The size of the packet is obviously going to affect the
timing for collision detection and avoidance.
I think these are the factors that determined the maximum size of the
ethernet frame in the original specs, but I'm admittedly just guessing.
Maybe someone else knows more of the details.
Jonathan
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Casey, Paul (6822)
Sent: Tuesday, October 21, 2003 6:04 AM
To: ccielab@groupstudy.com
Subject: Small Question....MTU size
Hello,
Can someone tell me why the MTU for IP networks is 1500 bytes.
I konw that the standard for ethernet 1500, but I am wondering why this
was
picked..
Why was an MTU of a1000 picked or what not an MTU of 5000.
Also apart from ethernet why does the MTU of serial interfaces default
of
1500 Bytes.
Was this an optimal value for something..?? maybe a trade off between
packet
header overhead with small MTU and increasing number of errors with
larger
packets...??
I have a problem getting a good answer for this, I asked one on the
experts
at work, but he said just thats the way it always was...???
Any help appreicated.
Kind regards.
Paul.
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