Subject: RE: Multiple Levels of LMM agents (was: RE: [mobile-ip] Revised Loca lized Mobility Management Requirement s)

From: Samita Chakrabarti <[email-masked]>
Date: Wed, 25 Apr 2001 12:46:50 -0700 (PDT)

> How to proceed?  Good question.  It would be really good if some other folks
> weighed in on the issue.  Does anyone who hasn't commented on this so far
> care to add anything?  care at all?
>
> Phil
>
>

IMHO, we need to be  careful what we decide as the requirement for
LMM or GMA or MAP ( however, we like to call it). Ideally, multi-level
hierarchy seems nice because the mobile can roam a broad geographical
area without ever sending binding updates to CN or HA. But, it comes with
a very high cost:
      - cost of designing a complex protocol, which may take
        long time for real deployment of MIPv6 and consequently IPv6.

     -- cost of maintaing the states within the multi-level hierarchical
        agents-- i,e when a MN moves from one chain of hierarchy to another
        the protocol needs to update all the routers in the new chain.
        (static host routes are not desirable and thus it needs a new protocol)

      -- For failure and recovery, either the protocol will be complex or folks
         will have to maintain multiple back ups.

     -- Are we gaining in any latency here  as opposed to sending a BU to
        a CN  and implementing MIPV6 fast handoff ?
        For data networking, I'd say in future, in most cases the CN location
        will be close by (with CDN). For VoIP, I expect that
        most of the cases we should either use route-optimization for MIPV6
        or use a HA which is close by (Ofcourse it depends on the business
        model).

     -- For most situtations the active communication takes place for short
        period of time, so if the coverage of LMM is reasonably large enough
        then less likely a MN will run into handoff situation

   How about thinking of an access network comprised of multiple MAPs at the
   same level serving a large geographical area and distributing the loads
   of MNs. Currently, when a MN moves from one MAP to another(in this scenario),
   we need to have MIPV6 type of mobility (or MIPV6 handoff). I wonder if
   it meets the cellular carrier's latency requirements ? If not, or some other
   non-technical business reason, access network does not want the MN to send
   BU to it's CN when it moves from one MAP (or LMM or GMA) to another, then
   it makes sense to develop some protocol to update the next LMM about the
   previous one and so on.
  
  But if multi-level hierarchy model seems to be inevitable in distant future,
   then how about making it  optional for the basic protocol
  and implementation and deployment of hierarchical mobility management.
  Sorry, I have not had chance to read all the emails on this thread.
  
  -Samita