nanog mailing list archives
Re: shim6 @ NANOG (forwarded note from John Payne)
From: Iljitsch van Beijnum <iljitsch () muada com>
Date: Wed, 1 Mar 2006 19:23:53 +0100
On 1-mrt-2006, at 17:22, David Barak wrote:
I think that we could spend our time better in coming up with a different approach to addressing hierarchy instead.
I agree.The address space is one dimensional. This means you can encode a single thing in it in a hierarchical manner "for free". With PA, that's the ISP: for any address, it's very easy to determine which ISP it belongs to and thus route the packet to that ISP. (We're so used to this that we don't even notice anymore.)
However, this doesn't work for multihoming because rather than a linear space starting with ISP A and ending with ISP Z we now have a matrix: A-A, A-B, A-C ... Z-X, Z-Y, Z-Z. (Worse with more than two ISPs.) You can't do a longest match first lookup on a multidimensional space, so in routing, every end-user becomes his own ISP and occupies a slot at the top of the hierarchy.
The thing is, it's not even hard to aggregate differently: just have router A hold the first quarter of the global routing table (0/2 with v4), router B the second quarter (64/2), router C the second quarter (128/2) and router D the fourth quarter (192/2), for example.
There is one snag, though: either you need four routers in each location, or you have to bring the traffic to the place where the router handling that part of the table is located.
Now I happen to think that we can massage this such that it's not necessary to add extra routers to speak of or backhaul traffic through places where it doesn't belong so basically all of this is free (no new protocols!), but unfortunately, I'm having a hard time convincing others that this is a workable approach.
Current thread:
- Re: Shim6 vs PI addressing, (continued)
- Re: Shim6 vs PI addressing Jared Mauch (Mar 02)
- Re: Shim6 vs PI addressing Owen DeLong (Mar 02)
- Re: Shim6 vs PI addressing David Barak (Mar 02)
- Re: Shim6 vs PI addressing Iljitsch van Beijnum (Mar 01)
- Re: Shim6 vs PI addressing David Barak (Mar 01)
- Re: Shim6 vs PI addressing Todd Vierling (Mar 03)
- Re: Shim6 vs PI addressing Stephen Sprunk (Mar 03)
- Re: Shim6 vs PI addressing Stephen Sprunk (Mar 03)
- Re: Shim6 vs PI addressing Roland Dobbins (Mar 03)
- Re: Shim6 vs PI addressing Andy Davidson (Mar 06)
- Re: shim6 @ NANOG (forwarded note from John Payne) Joe Abley (Mar 01)