Re: Sequentially assigned IP addresses--why not?

["Steven M. Bellovin" <[e-mail]>]

In message <[e-mail]>, "Cor
zine, Gordie" writes:
>Using the IP address, you index into a table with 100 M entries, pick up an
>index into the 75K entry routing table.  You now have two tables that
>require maintenance, that's all.  If customer changes ISP, their entry in
>the first table is changed.  Link is down, the second table's mechanisms
>handle it. Use a 64 bit processor architecture, memory is cheap.
>Re-architecting the Internet is going to become all but impossible.

The issue isn't table lookup; it's the routing table calculation (and, in 
the case of your particular example, the sheer amount of data that has 
to be passed around).  Put another way, how does each router know what 
should be in those 100M entries?
>
>Its a matter of separating routing from identification.

Phrased somewhat differently, there are a lot of people who agree, 
though it's still a controversial notion.  See if you can find a copy 
of draft-ietf-ipngwg-esd-analysis-06.txt (or -05) -- it's a description 
of the best worked-out proposal, plus a refutation of it.   (I disagree 
with the refutation, but I'm not going to go into that now -- I think 
that the proposal is sound.)  Briefly, the idea is to use the 
high-order 8 bytes of the v6 address for inter-site routing, and the 
low-order 8 bytes for host id.)

But that still requires hierarchical assignment and routing for the 
high-order 8 bytes.  *No one* knows how to do it any differently.
>
>Look, my days as an engineer are a distant memory, so I won't try to work
>this out in detail.

Mere assertions that it is possible, in the face of the prevailing 
wisdom that it isn't, just won't cut it.  Maybe you're right, maybe it 
can be done -- and if so, it won't be the first time that the accepted 
wisdom is wrong.  But the 

>  Maybe there are irrefutable reasons why this can't be
>done, but I do believe the current architecture will lead to premature
>exhaustion of the address space.

Apart from the fact that 128 bits is Really Big, v6 is supposed to have 
easy renumbering, so that we can renumber sites as they're move around 
to different pieces of the topology.



		--Steve Bellovin