On Thu, 26 Jul 2001 18:52:50 CDT, Jose Manuel Arronte Garcia
<marronte(_at_)ver(_dot_)megared(_dot_)net(_dot_)mx> said:
If the used 48-bit addresses in lower layer protocols, why they did not use
48-bit routing-enabled addressing for the Internetwork layer? Not just use
the very same addresses as I may have implied (I DO NOT mean that). After
all, they were using 48-bit addresses already.
First off, 32 was probably chosen because it was a number of octets(*)
that fit nicely into a register. Dealing with 48 gets more interesting.
Secondly, at the time, a 9600 baud leased line was a *high speed* link,
and 56KB was "long haul backbone link". The added 4 bytes/packet would
be noticable at that speed.
Third, they were doing a new design, and the old one (NCP) had a 256
host limit. I wasn't there, but I bet '4 billion will be PLENTY' was a
common sentiment - and understanding the amount of address space wasted
by subnetting and the eventual need for CIDR so routing tables could be
aggregated were still a decade down the road.
Valdis Kletnieks
Operating Systems Analyst
Virginia Tech