Subject: RE: [manet] A few RFC 3626 OLSR questions

From: "Dearlove, Chris (UK)" <[email-masked]>
Date: Wed, 29 Oct 2003 09:08:52 +0000

> I have a few questions on RFC 3626 OLSR. Your help is much appreciated.

Well, my answers aren't official, and I'm not going to justify them
with specific references to the RFC. However I have implemented it,
so I know something about it.

> (1) MID message. For a node with multiple interfaces, is the MID sent on
> each interface, or
> only on one interface? I don't see anything in the RFC saying about this. I
> may have missed it. 

It certainly needs sending on all interfaces. It's quite straightforward
to derive an example where the protocol breaks if you don't do this.

> (2) In section 6.1, Hello message format, under one "link code"  we may
> have multiple 
> "neighbor interface addresses", does it mean that if several neighbors have
> the same
> "link type" and "neighbor type", you'd summarize them and place them all
> under the same link code?

That's the efficient (in terms of HELLO message size) way to do it.

> One link can have only one neighbor interface address as defined in the
> link set, is that right?

If I understand your question correctly, yes, but I'm not 100% certain
what the issue is here.

> (3) When a node just comes up, its link set and neighbor set all empty, the
> node is 
> sending the first Hello message. What should it send in this message? Only
> the message
> header, no body? Or in the body place Htime, willingness and link code of 
> "UNSPEC_LINK, NOT_NEIGH"?

You need the Htime and willingness. However you don't need any link codes.
The message size (for IPv4 addresses) will then be 16, and if this is the
only message in the packet, the packet size will then be 20.

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From: "Grzegorz Jablonski" <[email-masked]>
Date: Wed, 29 Oct 2003 11:21:30 -0000

Hello,

I have a question about reliability of communication in 802.11 based ad hoc
networks. Specifically, there is a difference in reliability between
broacast and multicast communication.

I'm modelling communication in ad hoc networks. Broadcast is unreliable,
with no failure notification. That is, after node sends a packet, that
packet may get lost for any reason, and the application layer will not get
any notification from the underlying network layers. For unicast ( assuming
that sender an receiver are in comm range ) it could be either
1) fully reliable
2) unreliable with failure notification to app layer
3) unreliable without failure notification to app layer

It seems like 2 is reasonable, since unicast uses the protocol with
acknowledgements.
How is that with unicast messagges? Can link failure be sensed? Or, in case
of unsuccessfull communication, will the application layer be aware of it?

Greg