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Re: [manet] DYMO and other routing protocols
Philippe Jacquet wrote:
I would say that from a very broad perspective, on-demand protocols
discriminate routes with respect to time and proactive protocols
discriminate routes with respect to space. Personnally I have
preference to proactive approach because it is richer and gives
better internet legacy. Objectively the two approaches have their
advantages and drawbacks and the two should be considered.
I mostly agree (although I don't see the spatio-temporal discrimination,
not even the frequency-temporal :-)
I think the classification on-demand vs proactive is conceptual only,
helping frame one's mind around two ways of obtaining routes.
That classification can't really be used to pit a protocol vs another.
OLSRv2 document says it's proactive but I think an OLSRv2 implementation
must be able to obtain a route if it receives a app packet whose dst it
doesn't know, and if it doesn't have a default route. Making it on-demand.
Similary, DYMO says it's on-demand but it should advertise RREP (or
RREQs) periodically if it needs to maintain up to date information at
all times. Making it reactive.
OLSRv2 says it's 'table-driven'. But DYMO uses tables too.
Similar things apply to link-state vs distance-vector distinction.
I think I personally would like to escape this artificial classification.
In my humble oppinion.
Alex
This said, I don't think that on-demand and proactive approaches are
represented at the same level in MANET. OLSRv2 has "space"
adaptability: i.e algorithms which automatically adapt to space and
topology variety, including for instance the MPR mechanism. In DYMO I
don't see an equivalent "time" adaptibility that goes beyond the
default values in timers. I think this may explain why the protocol
performs great in some scenario and very poorly in other.
Some adaptability feature in DYMO would be welcome, not necessarily
proactive, but at least some memory based feature could help.
Philippe
David Murray a écrit :
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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