Subject: Re: [lisp] #5: LISP protocol version is alive and kicking

From: [email-masked] (Noel Chiappa)
Date: Tue, 22 Sep 2009 09:39:30 -0400 (EDT)

> From: Terry Manderson <[email-masked]>

    > g) TTL (clock sweep) can be used to maintain ITR mapping freshness.

I'm not sure about this one yet: we _might_ want an explicit mechanism
(piggybacked mapping versions or checksums) to check for stale mappings;
probably there will be some experimentation to see i) if stale mappings
are a problem, and ii) how well a piggybacked mechanism works, before
we can say for sure.

Also, there is a case we can handle, but haven't yet talked about in the
spec, which is a packet for EID X arriving at an ETR which is no longer an
ETR for the destination EID. That ETR might want to SMR the ITR (although
we need to make sure it's not a DOS vector), although I don't know if it
will be common enough to be worth putting in a mechanism to fix those
cases. Ditto for ICMP Port Unreachable (if the packet winds up at
something that's not a LISP ETR) - and that one's definitely a DoS vector.

    > Thus far I don't see any convergence on what the version looks like
    > in the map-request/map-reply (type value or otherwise)

The type value is 4 bits, that ought to be more than enough?

    > Is this a fair approximation of the current position?

Other than the ones I commented on, I think so.

	Noel

---

From: Terry Manderson <[email-masked]>
Date: Tue, 22 Sep 2009 22:24:33 -0700

> (piggybacked mapping versions or checksums) to check for stale mappings;

So you want to ask (or some other way) what the xTR has in mapping? If so,
it sounds weighty and akin to an open resolver. Or have I misinterpreted
what you are thinking?

> are a problem, and ii) how well a piggybacked mechanism works, before

If versions are to be transferred only in map-reply, my initial thoughts
would be that stale xTR mappings should be avoided otherwise the data
communication could probably fail due to a mismatch of data
header/encapsulation.

[..]
> The type value is 4 bits, that ought to be more than enough?

Assuming that the type value is how the WG and/or authors wish to handle the
version info inclusive of the alterations of section 6.1.4 of
draft-ietf-lisp to adjust the use of the type field, which is currently
specified as 2 (map-reply).

> Other than the ones I commented on, I think so.

Thanks

Cheers,
Terry