how are backups implemented?

Thu Sep 20 08:51:54 UTC 2001

[posting this message after having looked for answers elsewhere including
the archives, but found no satisfactory answers]

i wanted to ask the operations community about how backups are typically
implemented. i am more interested in backup implementations, in which a
failure would expose a different origin AS (this would exclude prepending
based backups).

1. when a network is multihomed, and one of the links fails, would you
expect a smooth transition (as seen in the bgp tables of a remote AS) from
one origin AS to another (modulo convergence effects)?

2. can a failure (anywhere in the network) ever expose another origin AS
for some AS's while it stays the same for some?  i guess it can, when the
network is being persistently announced from both origins, and under
normal scenario one origin could be hidden from some AS's. would this also
hold for a routing table as rich as routeviews?

3. can a failure ever cause more-specifics with a different (from the
origin of the less-specific) origin AS to appear (again, as seen from a
remote AS)? this might depend on how backups are implemented - so what i
am asking is, is this a common/possible case?

	thanks,
	-- ratul