multi-homing fixes

Wed Aug 29 18:04:31 UTC 2001

On Tue, 28 Aug 2001 bmanning at vacation.karoshi.com wrote:

> As a data point, I would ask that those whom are allowed to participate in
> the design discussions and are willing to be active in them, to take this
> request into those discussions.  I would like to see the ability to have
> the routing system support 2-32nd entries in the "DFZ" (whatever that is... :)

4 billion routes is not impossible, although I don't think one out of
every two people on the entire planet is going to multihome. 100 million
seems more reasonable. In either case, this means we have to find a
completely new way to look at routes. The current paradigm is that every
route is very important, so we should store as much information about it
as possible. This will have to change. If we remove all non-essential
information from a route, we finally arrive at the single thing that must
always be encoded for each route individually: whether it is reachable or
not. If we assign a bit of memory to every possible route, it is possible
to store the reachability state of the entire Internet as /24s in just two
megabytes.  Or as individual /32s in 512 MB.

Obviously, a lot of work has to be done to apply this to the real world.
An idea would be to assign /16s to geographic areas. Each ISP that has
customers in that area would announce the /16, just like they would do
now, but with an attached bitmap that indicates for which /24s this
announcement is valid and for which it isn't. So 10 ISPs in one area would
all announce the /16 with a 256 bit bitmap, so just 10 routes end up in
the default-free zone instead of 500.

Iljitsch van Beijnum