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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
>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
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