| at present our locators are AS numbers.
No, Keith, they are not.
The AS number does not describe a location in any sort of topology.
It is simply a representation of a set of routers with the same
routing policy, that should not receive via eBGP NLRI which
have originated from or passed through said routers.
The AS number is otherwise completely meaningless, although
the AS path itself is a funny sort of non-scalar metric.
(See the work of Ahuja and Labovitz for details on that).
A locator by definition must describe a precise location within
a network, such that any router will be able to forward traffic
towards that network using only the information in locator.
In IPv4, the locator *is* the IPv4 address, independent of
what inter- or intra-domain routing system is being used.
thanks for the clarification. I don't pretend to be a routing
expert; I just get into these discussions in an effort to
keep the proposed solutions for routing scalability problems
from harming applications.
but if AS#s aren't usable as locators, it seems like
it should be possible to use BGP to advertise mappings from
IP address prefixes to some other kind of locator, and to
base route computations on *those* locators rather than
on address prefixes. that would allow routers to
effectively aggregate routes for dissimilar prefixes,
at least for the purpose of route computations.
(even if the forwarding table still had to be indexed
by address prefix)
| if we change the system to use a different kind of locator we still
| need stable addresses, we still have to maintain the mapping
| function from addresses to locators, and we still need that mapping
| function to be current and reliable.
End-to-end/globally-unique identifiers are very convenient indeed.
However, identifiers and locators are different.
There is no reason to overload them, and it's a bad habit.
there are plenty of reasons why they are overloaded, it's just that
folks tend to overloook those reasons because they are focusing
on a single problem. some of them are outlined in another message
that I sent to the IETF list today.
It's also a bad habit to think that locators need to be
end-to-end or globally (rather than contextually) unique.
they don't have to be. it's just that if the locators are
context-specific then you can only use them for routing
within the context in which they're valid. (and you want
to make really sure they don't get confused with locators
from other contexts)
| what we are arguing about is the appropriate granularity of the
| mapping function, and the appropriate place to maintain that mapping.
No, we are not arguing about that, but these are indeed issues.
I think that's the fundamental issue - at least, given the other
constraints on the problem that seem to be imposed.
Keith