hi hannes,
first, i need to confess that i have disagreed with 'be liberal in what
you accept' from day zero. that way lies entropy.
> 5: Unsupported PDU Type (fatal): The PDU Type is not known by the
> receiver of the PDU.
>
> <-- this prevents seamless upgrading once we want to extend the protocol;
> why is this fatal ?
not exactly. it prevents chaotic pretend upgrading producing a bunch of
incorrect garbage in the router's database which leads to incorrect
validity decisions and thus incorrect routing.
imagine that the unrecognized pdu was signaling "flush all data with
origin AS 42," or "delete all roas for prefix P or longer."
> 6: Withdrawal of Unknown Record (fatal): The received PDU has Flag=0
> but a record for the Prefix/PrefixLength/MaxLength triple does not
> exist in the receiver's database.
>
> 7: Duplicate Announcement Received (fatal): The received PDU has an
> identical {prefix, len, max-len, asn} tuple as a PDU which is
> still active in the router.
>
> <-- why do we need to reset the session here for reasons 6 & 7 ? -
> in the spirit of "be tolerant what you receive" a receiving router
> can do the right thing w/o disrupting the session.
in general, all these indicate that the receiver and the sender are
seriously out of whack. e.g. if the receiver goes ahead despite 6 or 7,
the receiver's data are most likely incorrect in the sense that it will
[in]validate an update which it should not. if that's not fatal, what
is?
but, i think at root, we have a disagreement on the idea of requiring
'correctness.' as i said, i admit to being a naggumite.
randy
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