RE: Strange public traceroutes return private RFC1918 addresses

[Michael.Dillon () radianz com]

> 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
> replacement). 
 
According to this URL 
http://www.columbia.edu/acis/networks/advanced/jumbo/jumbo.html
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
time.

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