Steve,The benefit of private space is that each address can be used many times. Therefore the additional 16 blocks of private space proposed here could satisfy the need of a very large number of very large private networks, without consuming a single public address.
On the other hand, if the space is redesignated as standard public unicast, then it can be used once only. At today's rate of consumption, this would add a year or so to the lifetime of IPv4. Add to this the greater difficulty of transitioning the entire Internet to deal correctly with 240/4 addresses (which is likened to the challenge of IPv6 transition), and I suggest the only viable alternative is private.
Paul.--On Tuesday, 7 August 2007 2:48 PM -0700 Stephen Gill <gillsr at cymru dot com> wrote:
Hi David,In order to take advantage of 240/4, new code will have to be deployed and there are systems that cannot/will not be upgraded.Do you have some sense as to what those systems are, code versions, and how many? I know it is on the list of Juniper martians for instance.While an organization receiving a block out of 240/4 could conceivably guarantee none of their systems dropped 240/4 on the floor, it is a bit unlikely that the rest of the Internet could be trusted to behave similarly. As such, people who received 240/4 blocks would likely be quite unhappy.I see this as a similar challenge to what we have today, with an added systems component. Certain entities with newly allocated prefixes have already experienced reachability issues with their allocations due to stale or outdated filters. This was largely overcome with a bit of operational planning and foresight. At some level I could envision something similar for 240/4 whereby it could be allocated and de-classified as a bogon, and then tested for reachability using pilot/anchor prefixes after "sufficient" time has been given for vendors and operators to implement the change. Ongoing reachability testing (active and passive) could be performed from the newly debogonized ranges to see how reachability compares to previously allocated /8s in recent past. Granted, it would take some time, testing, and planning but is it not conceivable that reachability could be attained to similar levels as that of a normal newly allocated, de-bogonized /8? It seems worth considering if possible systems issues can be overcome with enough time given for planning if it extends the life of IPv4 by a reasonable amount. It would also be useful to put those considerations into the draft whatever the final concensus ends up being. -- steve
________________________________________________________________________ Paul Wilson email: pwilson at apnic dot net Director General, APNIC sip: apnic at voip dot apnic dot net http://www.apnic.net phone: +61 7 3858 3100