[ih] trailer encapsulation, was IPv4 address size debate

[johnl at iecc.com (John Levine)]

>    > There was at least one implementation of Ethernet (MIT? IIRC) that put
>    > the Ethernet header at the *back end* of the packet on the wire - i.e.,
>    > it became a trailer rather than a header. 
>
>Ah, no. That was Berzerkley. (See RFC 893.) (Gratuitous comment suppressed... ;-)

Trailer encapsulation was part of 4.2BSD, and it was a significant win
on the VAX, which had fairly slow memory and tiny 512 byte pages.  The
data part of the packets was padded to a multiple of 512 bytes so it
could be moved around both within the kernel and into user space by
adjusting page table entries rather than by copying.

R's,
John