Subject: [Ietf] 240.0.0.0/4

From: Iljitsch van Beijnum <[email-masked]>
Date: Tue, 20 Apr 2004 10:19:49 +0200

I was wondering if there are any plans to change the status of the 
class E address space (240.0.0.0 - 255.255.255.255).

Currently, there are approximately 221 usable /8s: classes A (125), B 
(64) and C (32). (0.0.0.0/8, 10.0.0.0/8 and 127.0.0.0/8 aren't usable 
at this time.) Adding 16 /8s from class E space would increase this by 
7%, and increase the unused address space with something like 20%.

However, it's almost certain that there are implementations out there 
that won't accept 224.0.0.0/4 as regular unicast address space. So if 
we want to be able to use class E space as such, it is imperative that 
we announce this a *very* long time in advance.

Two other possible uses:

It seems that there are now organizations who want/need more private 
address space than is available as per RFC 1918. Using class E space 
for this would make a lot of sense as this allows for a lot of private 
space without sacrificing usable unicast space.

In large networks, a lot of address space is used up and/or fragmented 
for point to point links and other infrastructure use. Using class E 
space for this could be a good compromise between using regular unicast 
space on the one hand or RFC 1918 space on the other hand.

Thoughts?

And is there a wg that deals / should deal with this issue?

Iljitsch van Beijnum

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