[Just to be pedantic ( :-) ) there are the equivalent of 219.98 'useable'
unicast IPv4 addresses if you use a unit of /8s (16,777,216 /32
addresses) (by my reading of the IANA IPv4 address registry plus
RFC3330).]
You appear to be saying that using 224.0.0.0/4 in contexts such as used
by the current RFC 1918 space does not sacrifice 'usable' unicast
address space. Surely, however, if these addresses are 'useable' in 1918
contexts they would be equally useable in a global context?
As a more general comment on your proposal, it appears that the
consumption rates of address space in the Internet for the past four
years are best modelled by a constant growth model of just under 4 /8s
per year (http://bgp.potaroo.net/ipv4/). That class E space is some 4
years of current average IPv4 address consumption rates.
I personally do not see any value in using this address block up in a
1918 role. My reasoning for this view is that life would be getting
mildly interesting if we ever reach the point when we are forced to use
this space, but life could be interesting a little sooner if we act now
to burn up this space for use in private / closed network contexts and
thereby make it completely unavailable to the public network. i.e. I
hope that collectively we, for some suitably large value of "we", will
manage this evolving situation so that the public Internet _never_ needs
to clamber into using the Class E space to sustain the continued growth
of the IPv4 public addressed network for some further extension of time
before the unallocated address pool completely dries up, but, for me, it
is some small comfort to know that if we do reach the point we we've
managed to assign, allocate and otherwise distribute these 219.98 /8
addresses, there is something left in the address cupboard marked 'E"
that conceivably is there to use if we really _have_ to.
Geoff Huston
At 06:19 PM 20/04/2004, Iljitsch van Beijnum wrote:
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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