Subject: RE: [mobile-ip] Revised Localized Mobility Management Requirement s

From: [email-masked]
Date: Thu, 19 Apr 2001 23:12:53 -0500

Erik wrote:
> 
> I agree in general.
> But I've heard arguments for having a hirarchy of agents 
> within each domain
> and I'm struggling trying to understand whether that is a 
> requirement or not.

I think the idea of allowing multiple agents and a hierarchy is to
have flexibility in deployment.  But I am not sure if multiple levels
will be truly required and to what extent does such a deployment
perform better with say a single level.

> Basically I see two approaches and I don't know how to resolve them:
> 1. A domain might be huge (for whatever reason) hence for 
> scaling reasons
>    you need to be capable of having a arbirarely deep 
> hirarchy of agents.

Why? Would this not work just as well with a single level of hierarchy,
but one where there are multiple top level agents, i.e a distributed
set of top-level agents which can load balance if that is a concern.

> 2. Simplicity is good idea and a solution without hirarchy is 
> likely to
>    be simpler, if not to implement to operate, than one with 
> a hirarchy.
> 

Completely agree here Erik. I know there have been arguments for
having a hierarchy, but I still do not totally get it. 

> This coupled with the size of the domain being a network design issue
> makes this hard to resolve.
> 
>   Erik
>

---

From: Jim Bound <[email-masked]>
Date: Fri, 20 Apr 2001 06:48:48 -0400 (EDT)

hierarchy permits distributing the problem set across that graph and a
vechicle to provide another level of indirection as required.  This gives
us the capability to address the scalability as Erik points out.  Load
balancing across multiple top level agents will cause the bottleneck above
the domain and it will have to be parsed there.  We need to remember that
we are dealing with a dynamic update environment and those updates may not
need to be done at the root of the domain in all cases.  As far as simple
to operate vs complex needs to be defined before we throw it out and part
of that engineering trade-off is perforance/cost too to build and procure. 
If done correctly the replacement of domain parts could be cheaper once
the hierarchy is set up and at the base of the hierarchy performance will
be better in the domain if going to the root is not required.  As far as
building it.  Thats a distributed problem I don't see an issue there. 

/jim