Subject: [netlmm] Review of draft-ietf-netlmm-mip-interactions-04

From: Christian Vogt <[email-masked]>
Date: Thu, 1 Oct 2009 15:03:06 -0400

Folks -

I have reviewed draft-ietf-netlmm-mip-interactions-04 and got a few
comments.  Please consider addressing those with the next revision of
the document.

The document is a useful deployment guide to network operators who
consider deploying Mobile IP and Proxy Mobile IP side by side.  It
describes three deployment scenarios in which Mobile IP and Proxy Mobile
IP co-exist, identifies potential issues in those scenarios, and
proposes solutions to the issues identified.

- While the three scenarios identified in the document are undoubtedly
   those that are most typical, it is not clear that this set of
   scenarios is exhaustive.  One way to make the exhaustiveness
   clearer, at least intuitively, is to break the co-existence space
   into only two high-level scenarios -- (1) hierarchical deployment
   and (2) alternative deployment of Mobile IP and Proxy Mobile IP --
   and to refine those further where needed.  Hierarchical deployment
   is what the document currently describes as scenarios A and C, where
   the difference between scenarios A and C is whether home agent and
   LMA are separate or co-located entities.  Alternative deployment of
   Mobile IP and Proxy Mobile IP is what the document describes as
   scenario B.  I believe that refining the hierarchical-deployment
   scenario, as the document currently does with scenarios A and C,
   makes sense given the notably larger number of issues that are to be
   considered if home agent and LMA are separate entities, compared to
   when they are co-located entities.  Still, the close relationship
   between scenarios A and C should, in my opinion, be emphasized more,
   perhaps by renaming the scenarios to “A.1” and “A.2”.

- Bullet 3 in section 3.3 (“Issues related to scenario C”) is missing a
   final sentence describing an adverse situation that may arise from
   the use of different re-ordering mechanisms in Mobile IP and Proxy
   Mobile IP.

- Bullet 4 in section 3.3 (“Issues related to scenario C”) describes an
   issue where a MAG registers a mobile node at a wrong LMA.  This
   issue is not specific to the co-existence of Mobile IP and Proxy
   Mobile IP.  It already exists in Proxy-Mobile-IP-only deployments.
   I suggest either stating this explicitly, or removing bullet 4.

- Suggest removing the last sentence in section 4.2 (“Solutions related
   to sce-nario B”).  This sentence does not add any information.  In
   fact, I am not even sure what it means.

Hope this helps.  Best regards,

- Christian