Subject: [lisp] Is there a dedicated control plane channel for interface to the Mapping system?

From: Linda Dunbar <[email-masked]>
Date: Fri, 1 Nov 2013 15:59:39 +0000

Dear LISP experts:

Is there a dedicated control plane channel for interface to the Mapping system? Or if the interface to the mapping system is via the data plane?

When the "Negative Map-Reply" is received by the requester, should the requester drop the packets to the desired target?

Thanks, Linda

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From: [email-masked] (Noel Chiappa)
Date: Fri, 1 Nov 2013 12:10:54 -0400 (EDT)

> From: Linda Dunbar <[email-masked]>

    > Is there a dedicated control plane channel for interface to the Mapping
    > system? Or if the interface to the mapping system is via the data plane?

If I understand your question, you're asking if anyone can ask the mapping
system for a mapping, or can only ITRs do that? (The ITRs are, I assume, what
you mean by 'data plane' - there is no wholly separate 'data plane' in LISP
as there is in some designs, because xTRs also include control plane
functions.)

If so, the answer is 'yes, anyone can ask the mapping system for a mapping'.

Also, I don't know if you've read:

  http://tools.ietf.org/html/draft-ietf-lisp-introduction-03

but if not, you should at least read Part I, which will help you ask questions
about LISP - that document is intended to be an easy, quick read.

    > When the "Negative Map-Reply" is received by the requester, should the
    > requester drop the packets to the desired target?

No, that just means that that destination is not a LISP host/site (i.e. it
does not have an {EID->RLOC} mapping), but rather is a 'legacy' host/site.

So the ITR (which is a border router for the source site, just one enhanced
with LISP functionality) should just forward traffic to that destination
'normally' (i.e. like any other IP router).

	Noel

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From: [email-masked] (Noel Chiappa)
Date: Fri, 1 Nov 2013 13:19:25 -0400 (EDT)

> There will be many ETRs, which ETR should ITR send requests? Does ITR
    > send requests to all ETRs? 

No, ITRs normally do not send Map-Request packets directly to an ETR - or
even a Map-Server.

An ITR sends Map-Request packets to a Map-Resolver, which is its 'portal'
into the mapping system. The Map-Resolver uses a distributed system called
DDT to find the Map-Server(s) which are responsible for the block of address
space the Map-Request is about. (This step may be avoided if the appropriate
delegation information is cached after it was received in response to a prior
request.) The Map-Resolver then sends the Map-Request to an appropriate
Map-Server, which forwards it on to an appropriate ETR.

	Noel