Subject: [manet] Suggestions for new problem statement

From: [email-masked]
Date: Mon, 02 Dec 2002 15:04:31 -0800

To all,

I would like to offer some suggestions for the new problem statement.  
Joe presented a preliminary problem statement that said the protocol 
should support up to 100 nodes, but I know this is up for discussion.

At the meeting in Atlanta, at least one person suggested 
that we not limit ourselves to only 100 nodes since some or all
of the proposed protocols can already support more than that,
and I agree with this.  

I know that AODV, TBRPF, and OLSR can all support at least 250 nodes
and probably more, using 802.11 with rate 2 Mbps.

I think the protocol should be as scalable and efficient as 
possible without being "too complex", and without using
hierarchical routing.  

It is generally agreed that the protocol should be extendable
to a scalable protocol (e.g., using a hierarchical method such
as landmark routing).
HOWEVER, IF THE PROTOCOL CAN SUPPORT MORE NODES WITHOUT USING
HIERARCHICAL ROUTING, THEN ITS HIERARCHICAL EXTENSION WILL
SUPPORT MORE NODES.  (The same is true for other scalability
techniques such as HSLS and FSR.)

Perhaps the problem statement can give 100 or 250 nodes as a 
*minimum requirement*, and state that when alternative techniques are 
available that are reasonably simple and well understood, preference 
should be given to techniques that perform better, e.g. that:

  1. Support more nodes 
  2. Support a higher level of mobility and dynamics
  3. Have better delivery ratio and end-to-end delay
  4. Provide shorter paths
  5. Generate less overhead (or "total overhead")
  6. Support lower bandwidth links 

We also need to be careful about stating the minimum requirements for
mobility.  For example, the number of topology changes per second for 
nodes traveling 20 mps according to the random waypoint model is much 
greater in an urban environment than it is in an open field.

Richard 

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From: Scott Corson <[email-masked]>
Date: Tue, 3 Dec 2002 15:04:48 -0500

Richard,

IMO this discussion is a rat hole for this group.

The ANS (Ad hoc Network Scaling) research list is being established (should
be available soon) for just this purpose and more.  It will be an open
research subgroup.  The work there will objectively evaluate all the issues
you raise and others, and will consider the performance of existing MANET
proposals as well as possible variants/crazy ideas ;-) for comparison.

I think there should be no notion of a *minimum* requirement for IETF MANET
WG scaling.  We should not overly concern ourselves about this issue in the
IETF.  Just build robust, stable protocols that work under a variety of
common situations, while we ascertain the boundary/scaling/stability
conditions where these protocols fall apart in the IRTF, to see
when/where/how/why/if additional work is required.  Frankly, the wide range
of possible traffic loadings and network dynamics can swamp all other
considerations, rendering specification of a minimum size quite pointless.
10 nodes or 250... either number can hold (or not), depending on a whole
host of assumptions.

I don't believe we should even list 100 nodes as a requirement... I think
network scale should be a non-goal in the IETF work.  Common sense
engineering should be able to produce reasonably efficient protocols without
needless overspecification.

-Scott

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From: Scott Corson <[email-masked]>
Date: Tue, 3 Dec 2002 15:04:48 -0500

Richard,

-Scott

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From: Joe Macker <[email-masked]>
Date: Tue, 03 Dec 2002 16:37:33 -0500

>10 nodes or 250... either number can hold (or not), depending on a whole

Scott I tend to agree.  Heavily quantifying minimum size or means little without spelling out a whole host of other metrics and scenario specific related issues (which defines a RATHOLE argument space for generality).... Mea culpa for throwing such numbers up in the strawman.  Speed is also not a generic metric for mobility because it doesn't take into account the variables relating to the scale of relative motion across a wide range of scenarios.  Also, in my opinion MANET technology is not just about handling potential relative motion but also about simple wireless link dynamics and time varying interface behavior.

To reiterate the proposal in Atlanta, we should focus in on simple, practical approaches in the IETF MANET realm that work for a variety of more commonly envisioned scenarios (and I believe we have some good engineering lessons learned finally on the table to build of off..) The ANS will serve to debate the larger scale analysis, performance tweaks, and design choices.  Within the IETF scope, after our initial EXPERIMENTAL targets, I would be more interested in achieving the goal of simple operational robustness and flexibility for basic cases at the engineering level.  Some may say we have that already, but what we don't have is consensus on a common WG engineered approach.  In addition, if we can design a degree of extensibility into any adopted core framework(s) we are in reasonable good shape for the future enhancements that will certainly come along.

Let's hear from more of you on this...