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Re: [manet] DYMO and other routing protocols


Hello folks,

I am quite hopeful that we can get to a converged
routing protocol that will subsume the best aspects
of DYMO and OLSR.  We have many recent
results pointing the way forward, some of which
I presented at the last IETF.  I am hoping to have
a much more complete presentation ready for the
next meeting.

I think it is clear by now that proactive protocol
operation is better when either there is a strong
requirement for minimizing latency in an uncongested
network, or when the traffic patterns are not very
sparse.  So, for instance, if most nodes in an ad
hoc network have open communications with most
other nodes in the same network, the communication
pattern is not at all sparse.  The tricky point is to find
out how dense the traffic pattern needs to be in order
to favor proactive operation (or, alternatively, how
sparse the traffic has to be in order to favor
reactive operation).

Furthermore, it is quite likely that some routes
should be proactively maintained even if route
table entries are generally acquired on demand.
The canonical example is that nodes need a
route to a gateway [if one exists] (or default router)
often enough that the route should always be there.
Whether this is done by periodic advertisement or
by triggered route repairs is a matter for further
study.  One could imagine similar requirements
might be imposed for important servers in the
network (e.g., certificate authority, data sink, ...).

I do _not_ think that proactive protocols should
automatically be the choice for mesh backbone routers.
Certainly not for all mesh clients...!  I would really
question whether it is needed for all other mesh
points anyway.  Plus, the whole concept gets quite
fuzzy if there are intermittent long-range connections
to neighboring meshes (as an example).

Regarding the naming of AODV vs. DYMO: this is
a long story with as much political as technical content,
and for my own part the former was by far the more
persuasive factor to persuade me to agree to a new
name for the standards-track reactive protocol.
Now the downside is that we have exactly the confusion
in evidence currently for newly interested parties.  Perhaps
we should rename DYMO to be AODVv2 :-)

Finally, regarding: 
  I think each protocol and its supporters can easily make a case
where it will beat other protocols. Simply look at conference
publications for good examples.

Simply stated: caveat emptor.

Stated more verbosely and redundantly using more words
and so on...
---> it is very important to fully understand the range
        of applicability for each research result.  These are
        sometimes not stated very clearly.  It is also very
        helpful, when possible, to understand the motivations
        of the authors.

Regards,
Charlie P.


ext Ian Chakeres wrote: 
There is no winner takes all in the contest of routing protocols for
MANET. I think each protocol and its supporters can easily make a case
where it will beat other protocols. Simply look at conference
publications for good examples.

That said, we have chosen to standardize DYMO and OLSRv2 - one
reactive and one reactive protocol in the MANET WG. For more
information regarding when one might deploy one or the other, please
see the applicability statements in the drafts.

DYMO is a successor to AODV (and other reactive protocols). The
specification is chartered to become a proposed standard. AODV is not
being actively discussed or standardized in the WG.

Ian

On 6/6/07, David Murray <30179198 at student.murdoch.edu.au> wrote: 
Hi,

I am wondering how DYMO fits in with the other routing protocols. I
have read a number of papers that discuss how on-demand routing
protocols like DSR/AODV work better in highly mobile environments where
movement is fast, CPU and memory are low and batteries are limited.
Equally, in situations where movement is very low, and there are no
power limitations, protocols like OLSR/TBRPF/STAR perform better.

So, I have a mental picture of OLSR/TBRPF being predominantly used in
stationary 802.11 mesh devices and AODV/DYMO being used to connect
users mobile devices ush as phones and PDAs. Is this correct or are
things not quite as simple as this? (I know RFC 2501 discusses MANET
applications and characteristics but the discussion is quite general)

If this is correct, it seems to me that DYMO and AODV are used in very
similar situations (the ad hoc interconnect between users devices). I
am aware that DYMO is a simplified version of AODV both in code and
network operation. It seems like the major difference is the path
accumulation feature in DYMO which allows nodes to append their
information to a RREP to give other nodes better knowledge of the
topology. It also seems that the hello feature has been removed in
DYMO. So, is DYMO likely to be a replacement for AODV or do they have
different uses/applications?

Thanks for your time

Dave


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