Subject: RE: [netlmm] #55: Define desired scalability more precisely

From: "Narayanan, Vidya" <[email-masked]>
Date: Tue, 30 May 2006 18:35:12 -0700

> 
> On Fri, 26 May 2006, Narayanan, Vidya wrote:
> > For e.g., if the NETLMM protocol had limitations in the 
> number of LMAs 
> > that can be present for the protocol to function properly, 
> that would 
> > be a bad protocol design.
> 
> You seem to be making an unqualified statement, "more 
> scalability equals a better protocol".  I don't think it's 
> that black and white; it might be that a simpler protocol 
> which would have limitations on the number of LMAs could meet 
> the requirements much better than a protocol which offers 
> unlimited scalability; scalability is one features, and 
> features usually come at a cost.
> 
> It all boils down to the requirements for the protocol.  As I 
> said, I think protocol should be able to easily scale to, 
> say, O(10K) simultaneous users in a single subnet.  Is there 
> even experience of anything even close to that range?
> 

I am still confused by having a number of users associated with protocol
requirements. What does it mean that a protocol scales to 10k users?
With one box? Multiple boxes? This seems like a box requirement to me.
And, I'm not sure what it means to have a limitation on the number of
LMAs - the protocol defines a functional entity called an LMA - how many
users a given LMA can support is really an implementation/system issue. 

OTOH, NETLMM should specify whether or not it is possible to have
multiple LMAs on a given subnet - this will affect system design and is
important input for system designers considering NETLMM. However, once
the protocol is designed to allow multiple LMAs on the same subnet, I
don't see why it should restrict that number to any value. 

Maybe I am missing something, but as of now, I still see the number of
users/LMAs as a deployment requirement, rather than an protocol
requirement. 

Vidya

> > This itself is a valid concern and I do believe that an 
> applicability 
> > statement or the like in the document must be added to clarify that 
> > there are limitations in making the LMM domain bigger and bigger.
> 
> An applicability statement is good, but IMHO the WG first 
> needs to agree what is the scope of the problem being solved 
> -- otherwise this issue is going to be revisited again and again.
> 
> I don't wish to see statements like, "[proposed] solution X 
> has bad scaling properties" unless we've agreed on the 
> required scaling properties first.
> 
> -- 
> Pekka Savola                 "You each name yourselves king, yet the
> Netcore Oy                    kingdom bleeds."
> Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings
> 

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From: "James Kempf" <[email-masked]>
Date: Wed, 31 May 2006 00:49:16 -0700

I'd like to get discussion on this issue closed by Monday so I can get the 
draft edited and submitted.

Seems like we have two opinions that the issue is an implementation issue 
and not a protocol issue and one that it should be stated as a protocol 
issue in the PS draft. One poster also had an opinion about what the 
potential scalability was but not specifically whether it should be stated 
as a protocol issue.

Does anybody else have any opinion on the issue?

            jak

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From: Pekka Savola <[email-masked]>
Date: Wed, 31 May 2006 12:42:58 +0300 (EEST)

> users a given LMA can support is really an implementation/system issue.

First off all, you seem to be assuming that inter-LMA "handover" is 
not service-interrupting.  That may or may not be the case, as 
multiple LMAs are out of scope.

Hence, you already seem to have a protocol requirement that it's 
possible to deploy multiple LMAs, and that handovers between ARs which 
connect to different LMAs are seamless.  Correct?

The number of users hides a number of other, more specific 
requirements which depend on the actual solutions.  For example,

  - whether you need to be able to deploy multiple LMAs for load
    balancing purposes (rather than just high availablility) yet still
    retain NETLMM benefits
  - whether a service provider can expect to deploy a single NETLMM
    domain for all its users instead of using another mobility
    management solution some handovers.
  - the amount of signalling (e.g., relating to movements, DAD,
    security, ...)
  - the amount of state at all ARs, at all LMAs, at the specific ARs
  - the amount of packet duplication required if IP subnet emulation is
    used ("pinging all-hosts multicast address")