legacy /8

Fri Apr 2 23:03:07 UTC 2010

On Apr 2, 2010, at 6:38 26PM, Andrew Gray wrote:

> Jeroen van Aart writes: 
>> Cutler James R wrote:
>>> I also just got a fresh box of popcorn.  I will sit by and wait
>> I honestly am not trying to be a troll. It's just everytime I glance over the IANA IPv4 Address Space Registry I feel rather annoyed about all those /8s that were assigned back in the day without apparently realising we might run out. It was explained to me that many companies with /8s use it for their internal network and migrating to 10/8 instead is a major pain.
> 
> You know, I've felt the same irritation before, but one thing I am wondering and perhaps some folks around here have been around long enough to know - what was the original thinking behind doing those /8s? 
> I understand that they were A classes and assigned to large companies, etc. but was it just not believed there would be more than 126(-ish) of these entities at the time?   Or was it thought we would move on to larger address space before we did?  Or was it that things were just more free-flowing back in the day?  Why were A classes even created?  RFC 791 at least doesn't seem to provide much insight as to the 'whys'. 

Many large companies found that class A nets weren't very useful.  Multiple levels of subnetting didn't exist, which meant that you couldn't assign a /16 to a location and a /24 to each piece of thick yellow cable within the location, for example.

AT&T got 12/8 moderately early.  We realized we couldn't easily use it, and offered it back in exchange for the equivalent in class B space.  Postel gave us the latter (135/8), but told us to keep 12/8 -- other people were discovering the same problem, so there was little demand for class A networks.  (This was circa 1987, if memory serves, and possibly a year or two earlier.)

		--Steve Bellovin, http://www.cs.columbia.edu/~smb