Subject: Re: [Roll] review/comments on overview-protocols

From: Philip Levis <[email-masked]>
Date: Tue, 1 Apr 2008 09:01:46 -0700

These are some excellent points, Ian. Details inline.

On Mar 31, 2008, at 12:25 PM, Ian Chakeres wrote:
> Here are some comments I have from reviewing the overview-protocols  
> document.
>
> I think you should consider including proactive/reactive in the  
> routing protocol taxonomy.

> You may also want to discuss distribution of a default route.
>

Both of these are good points. The first one especially so, because it  
will give insight on why the analysis plays out like it does.

>
>
> On page 6 you bring up neighbor discovery. I would recommend you  
> change the terminology to avoid the term "neighbor discovery (ND)".  
> ND has very specific connotations within the IETF. I might recommend  
> adjacent router discovery. You might also want to mention asymmetric  
> reachability  (see ND RFC), since this behavior will be common in  
> ROLL networks.

This is a good point. We want to be careful about terminology.

>
>
> RIPng and DYMO use distance as a metric.
>
> AODV has some weird behaviors when multiple messages are received  
> with different delays that make it not simply dependent on hop  
> count. My paper discusses it === Ian D. Chakeres and Elizabeth M.  
> Belding-Royer. "Transparent Influence of Path Selection in  
> Heterogeneous Ad hoc Networks." Proceedings of the 15th IEEE  
> International Symposium on Personal, Indoor and Mobile Radio  
> Communications (PIMRC), Barcelona, Spain, September 2004. ===  
> Several of these observations/features are also available for DYMO.
>
> Using the methods (delay or distance) above both AODV and DYMO can  
> include node metrics such as energy in their route discovery. This  
> behavior may influence Section 5.2.
>
> In Section 5.3 you mention GPSR, please include a reference.
>
> In Section 5.4 you state that AODV headers are 24 bytes. This seems  
> to be stated as protocols not being built to support small MTU, but  
> I would argue that 24-bytes is a small packet in comparison to most  
> other proactive routing protocols.

Very true. It is important to give values for more protocols, so a  
reasonable comparison is possible.

>
>
> In Section 5.4, you might want to mention 6lowpan as one solution  
> for handling ROLL small MTU problems.
>
> In Section 5.5 you discuss sleepy nodes. I see sleepy and low power  
> as related but distinctly different problems. Perhaps you can make  
> sleepy a subsection of low power.
>
> In Section 5.7 - I have been working hard to incorporate mechanisms  
> to enable MTR in all the MANET protocols. The draft is draft- 
> chakeres-manet-manetid. It has been discussed on list and I plan to  
> include it in DYMO.
>
> I'd like to say a few words about DYMO. DYMO has lots of optional  
> behavior and only the most fundamental behaviors are required. For  
> example, path accumulation is optional. Even forwarding a RREQ is  
> optional. Expanding ring search is optional. Interactions with relay  
> sets are optional. Although not described - precursor lists could be  
> implemented and they could be used to control RERR propagation.  
> These optional behaviors allow an intelligent implementation to  
> perform well in a larger number of scenarios.

Good point. I guess part of the trick here will be to figure out how  
to characterize DYMO given its many options. Having 20 or so different  
DYMO variants in the table is not particularly helpful. Perhaps the  
place to start might be what TYMO uses, which is essentially DYMO in  
its most stripped-down form.

>
>
> The discussion of DSR in the appendix seems quite weak when compared  
> to the other protocols.
>
> Feel free to share this with the other authors,
> Ian
>
> One more thing - Here is a comment related to the current on-list  
> discussion about which protocols to include in the analysis - should  
> mobile IP and other tunneling protocols be included? I say no, but  
> many (e.g. MANEMO) people may say yes.
>

I am tempted to say no: those are (effectively) overlay routes over  
existing L3 routes, while what we're concerned with here are the  
underlying L3 routes. Now, one could have a subset of underlying L3  
routes and use them as waypoints for the overlay, which then fills in  
the rest, but I suspect that such a protocol would look very different  
than mobile IP and such.

Phil
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From: "Ian Chakeres" <[email-masked]>
Date: Tue, 1 Apr 2008 23:31:49 +0530

Comments inline.

>  its most stripped-down form.

I'd like to say that these "variants" are all compatible and interoperate.

The challenge with basing the performance on a "stripped-down" version
of DYMO, is that the stripped-down version may perform very good or
very bad in certain scenarios. For example, path accumulation can be
considered very good if it reduces the number of route discovery
attempts. On the other hand, if this information isn't used (and
therefore doesn't reduce the number of route discovery attempts) it is
considered a waste. I think lots of the optional features enable
implementors and nodes to make intelligent tradeoff decisions.

>  the rest, but I suspect that such a protocol would look very different

I agree with you, but I also think these items might come into more
play when we discuss the network size and what hierarchy is
desired/used/required for ROLL networks.

Ian