Subject: Re: Call for Comments on Issues ID

From: [email-masked] (Joseph P. Macker)
Date: Wed, 11 Feb 1998 18:09:43 -0500

At  3:15 PM 2/11/98 -0500, Ken Carlberg wrote:
>now perhaps i missed something inthe draft or in previous discussions,
>but one issue that seemed to be missing is the impact on potential data 
>loss caused by reactive algorithms.  by this i mean that if the depth
>of the ad-hoc network (number of hops from edge to edge) is great, or
>the algorithm contains a number of iterative steps to generate a route
>from scratch, then it would seem some amount of packet loss can be
>experienced at the first ingress router.  further, it would seem that
>this type of packet loss (i.e., the first few packets in a session)
>could be either inconsequential or quite disruptive depending on the
>application used.
>
>thoughts ?
>
>-ken
Ken:

I think this is a great point...a brief discussion of this performance
consideration should be included. I think that would suffice for this broad
performance considerations framework. Do you agree?

I do believe this is something interesting to look at in future simulations
with upper protocol stacks (transport,application) running over candidate
manet routing protocols.  This is a performance tradeoff area that needs
more addressing.

-Joe

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From: Chip Elliott <[email-masked]>
Date: Wed, 11 Feb 1998 23:28:08 -0500

Ken,

I believe that (in practice) this is extremely important. The same
thing goes for "route repair" operations, where during some kind of
flow the node moves within the network.

Two areas of particular concern, to me at least, are the interaction
of TCP with route discovery/repair, and the effects on slow-periodic
"push" information such as GPS location. I believe that some of
the algorithms discussed in MANET would result in very sluggish TCP
connections, due to the way that TCP back-off works. And they would
also have a different kind of trouble with more esoteric types of
data distribution, eg military situational awareness, because
the "push" operations would happen infrequently enough so that the
network would lose all cached routes and have to rebuild them each
time.

I'm never sure exactly what level of detail we should be hitting
in MANET, but I do second Joe's remark that these are very important
issues to raise.

Cheers,

Chip Elliott

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From: Ken Carlberg <[email-masked]>
Date: Thu, 12 Feb 1998 12:02:14 -0500

> performance considerations framework. Do you agree?

yes.  chip brings in a good point about the relationship of tcp 
adaptive algorithm and its relation to soem of the proposed MANET 
algorithms.  other examples could involve applications that use
single-shot (unicast/multicast) queries, or anycasting.

-ken