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RE: Strange public traceroutes return private RFC1918 addresses

  • From: Michael.Dillon
  • Date: Wed Feb 04 05:28:12 2004

>And why 4470 for POS?  Did everyone borrow a vendor's FDDI-like default
>or is there a technical reason?  PPP seems able to use 64k packets (as
>can the frame-based version of GFP, incidentally, POS's likely
According to this URL
which you have seen before, the number of CRC bits in the protocol
header limits the number of bytes you can practically use for the
MTU. I expect that we won't go beyond 9000 byte MTUs for a long

The 4470 for POS probably comes from Token Ring originally. In the
original 4 Mbps token ring a device was allowed to hold the token
for 9.1 ms which was enough time to transmit 4550 octets. This timing
was probably adopted by FDDI which borrowed a lot from the token
ring design. No doubt, the designers of POS were also influenced by
token ring and just chose the same size.

--Michael Dillon