Re: [RAM] ViP: Anycast ITRs in the DFZ & mobile tunnels

[Robin Whittle <rw at firstpr.com.au>]

Hi Dino,

You wrote:

> Can you tell me what is different here than LISP plus the use of
> NERD?

  http://tools.ietf.org/html/draft-lear-lisp-nerd

My understanding of LISP may be faulty, but I thought that the IP
addresses which are used as locators do not come from prefixes which
are advertised via BGP.  Therefore, to my understanding, if a host
in an edge network wants to send a packet to such an IP address, the
edge network needs a LISP ITR function in one or more routers -
either inside the edge network or at the border router.

Maybe what I wrote only exposes my misunderstanding of LISP and of
other aspects of routing and addressing.  If so, hopefully this will
have some educational value for others.

My mention of anycast is probably wrong.  What I want to achieve is
multiple routers such as transit or border routers to perform the
ITR function, and my plan was that they would all advertise the same
prefix: 22.22.0.0/16.  I don't know if there is a precedent for this
with BGP or whether it is impossible, but anycast is a separate
technology which is probably not needed here.

>>      However, it would be technically possible to have the ITR
>>      function performed by a single-homed border router or by
>>      specialised router which has only a single interface which
>>      connects to a transit router or to any border router.  

. . .

> Tell me what is different here than a LISP ITR running on a CE router
> with BGP enabled?

There's no technical difference.  Its just that, as I understand it,
 with LISP, the edge network needs to run an ITR if its users are to
be able to send packets to LISP-mapped addresses.

I am going out and will reply more fully in the next day or so.

   - Robin


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