On Wed, 13 Nov 2002, William Ivancic wrote:
> I'm not sure about the largest or smallest MTU size, but I thought it may
> be appropriate to note some behaviors and problems we were having with MTU
> discovery over mobile networks using mobile-IPv4 double tunnels and
> encryption. The mobile-IPv4 mobile networking we are using applies double
> tunnels from the home agent to the foreign agent when foreign agent service
> is used. Adding encryption on top of that hides MTU discovery. To add to
> the problem, somewhere the don't fragment bit is being set - perhaps in
> some applications or at some Web servers. Thus, we manually have to set
> the Max MTU in the hosts on the mobile LAN or set the minimum acceptable
> MTU size at the last visible interface to the mobile LAN.
I'm a little curious to know how you think this is supposed to work. If you
are using any advanced TCP features (e.g. PAWS RFC1323) or IPv6 then DF becomes
mandatory.
I think that our algorithm will indeed solve your problem for the TCP based
applications, although I can't tell from your message what is the MTU of the
inner most tunnel. It sounds like 1500 - 4*tunnel_overhead. Is that correct?
What was the actual size?
Thanks,
--MM--
----------------------------------------------
Matt Mathis <mathis@psc.edu> W:412.268.3319
http://www.psc.edu/~mathis H:412.654.7529
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