1430MTU, MRU, and MSS
- Nov 4, 1998Question about PPP MTU/MRU sizes and how they affect the MSS being
advertised in various implementations:
RFC 793 states unequivocably that the local network's MRU should be used
for the value that is advertised in the MSS:
Maximum Segment Size Option Data: 16 bits
If this option is present, then it communicates the maximum
receive segment size at the TCP which sends this segment.
However, many of the systems I've been testing don't seem to do this,
instead choosing to advertise a (predetermined) fixed size that has no
relation to the negotiated MRU. Also, some systems seem to use the MTU
for the MSS, even though MRU should be the deciding factor since A) the
spec says so, and B) anything larger would fragment.
Does anybody have a good reason for not defining MSS based on MRU?
Eric A. Hall ehall@...
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