The IP over ATM Mailing List Archive by date

[Masataka Ohta <mohta@necom830.hpcl.titech.ac.jp>]

> As far as I understood Masataka's reply, the CSR model relys
> on the CSR breaking the internal short-cut as soon as IP level
> routing algorithm's operation discovers the existence of an external
> loop.

No.

The CSR model relys on the CSR breaking the internal short-cut
as soon as IP level routing algorithm's operation resolves the loop.
                                                  ^^^^^^^^

CSR decides cell forwarding direction based on a local IP routing
table.

> After a brief transient of looping packets, the CSRs effectively
> switch back to 'TTL decrementing' mode (aka normal router).

CSRs always decrement TTLs of RSVP signalling messages.

So, you can, at least, detect the existence of the loop.

> Is it reasonable? (i.e. do IP routing protocols
> detect loops 'fast enough' ?

i.e.? Do you think a loop for resource reserved communication so
harmful? Beause it is resource reserved, it won't affect other
communications. Right?

But, first of all, no real resource is consumed by the loop. As the
cell forwarding loops would be established with RESV messages, which
travels from receivers looping RESV messages can't reach the sender.
That is, no data will actually flow in the loop.

Moreover, because RESV messages are merged, reservation is made
only once, even if RESV messages loop.

Then, if resource comsunption, IF ANY, is confined, the remaining
problem of the loop would be the inability of the original
comunication, which is, anyway, impossible, even if the packets
are dropped because of zero TTL checking.

So, what is your problem?

						Masataka Ohta