Subject: Re: ip reassembly time exceeded?
To: Perry E. Metzger <>
From: Jonathan Stone <jonathan@DSG.Stanford.EDU>
List: current-users
Date: 01/27/1997 19:00:52
>No. This is untrue.

>You are required to be able to REASSEMBLE a 576 byte packet. You are
>NOT required to be able to transport one, although it is recommended
>that you be able to do so.

Perry is of course correct. See rfc1122 for authoritative details.
The 576-byte MTU requirement is an oft-repeated canard for IPv4.  So
much for Microsoft Internet engineering.

However,  I _think_ an 576-byte MTU may be required for IPv6,
since 576-byte MTUs are allowed for multicast traffic. Fragmentation
and reassembly is the responsibility of host-systems in IPv6; hosts
should use path-MTU discovery and fragment accordingly, but
there's currently no good way to negotiate a path MTU over a dynamic
multicast tree....