North American Network Operators Group

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Re: Ethernet NAPs (was Re: Miami ...)

  • From: John Kristoff
  • Date: Thu Aug 23 09:59:42 2001

Leo Bicknell wrote:
> I just have to speek up that this is all very well and good, but
> it's also a good way to make a NAP that doesn't work.
> If you don't, the behavior is simple.  A 9k MTU GigE arps for a
> 1500 byte FastEthernet host.  Life is good.  The TCP handshake
> completes, life is good.  TCP starts to send a packet, putting a

Furthermore... Larger frames would be nice if all hosts supported them,
but the problem is that the that most end hosts cannot and probably will
not ever support so called jumbo frames.  What does having 9K ethernet
frame support at a NAP get us?  If one end of the connection, all those
1500 MTU end hosts, don't support large frames fragmentation may have to
occur somewhere and that would probably be worse.  With fragmentation,
the performance problem is pushed closer out to the edge and the edge is
probably where the performance benefit is needed so it could be a step
in the wrong direction.

Perhaps the one good approach to jumbo frames is to make use of the
networking layer and ensure hosts are doing Path MTU discovery to avoid