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

From: "Narayanan, Vidya" <[email-masked]>
Date: Fri, 26 May 2006 19:12:27 -0700

Hi Pekka,

<snip>

> 
> I'd rather state explicitly that the solution must be able to 
> scale to, say, O(10K) or O(50K) simultaneous users.  

I can't understand the reasoning behind explicitly stating any number
here. Any numbers for scalability are system level requirements and not
protocol level requirements. The only goal of a protocol should be that
it be scalable - in the sense that in a real deployment, it must be
possible to *scale up/out* the protocol. 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.
But, as long as more users can be supported by increasing the number of
LMAs and/or ARs, the protocol itself is scalable. System level
scalability requirements can then say x number of simultaneous users (to
figure out how many actual boxes are needed) or x number of users per
LMA, etc., but this is outside the scope of the protocol itself. 

> If the 
> implementations can work on the scalability to make that much 
> higher -- that's great, but not something we in the IETF 
> should be concerned about, because networks can just deploy 
> more boxes without significant disadvantage to the user if 
> the limit is reached.
> 

As I said above, I don't think the numbers mean anything to a protocol
and should not be part of any protocol requirements. 

> It seems to me that as soon as we discard Mobile IP as a 
> basis for localized mobility management, there seems to be 
> push to make the LMM domain bigger and bigger so that you 
> could make do without any non-LMM mobility management 
> solution.  As shown in the list a)-f), building one LMA/MAP 
> big enough to cover the whole world (or break users' 
> session if (s)he moves e.g. from one city to another) just 
> doesn't seem feasible, so I can't figure out why we're trying.
> 

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. 

Regards,
Vidya

> -- 
> 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: Pekka Savola <[email-masked]>
Date: Sun, 28 May 2006 13:56:39 +0300 (EEST)

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?

> 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.