Subject: Re: [manet] Re: [geeks] Fwd: [BAWUG] I have a dream

From: S Woodside <[email-masked]>
Date: Wed, 9 Apr 2003 17:33:34 -0400

On Tuesday, April 8, 2003, at 04:51  AM, Adam Megacz wrote:

>
>>>> Source Routing is the only scalable solution.
>
>>> ??? broadcasting routing requests doesn't seem that scalable.
>
>> source routing and routing requests broadcasting are 2 different 
>> things.
>
> Exactly.  PSR isn't so much about the route discovery as it is about
> the routing algorithm and addressing structure.  Geographic techniques
> could be used to augment route discovery without altering the rest of
> the protocol.  Simon, do you have any suggestions on the best way to
> do this?

Nothing concrete. Perhaps geographic routing would be the default and 
in a Source routing scenario, the source routing discovery and routing 
would only be used on links that don't have geo knowledge at both ends. 
So that, on any given link, the router will examine the packet header 
first for a geographic address, and if it knows how to route it 
geographically, will ignore the source routing table in the packet 
header. That could cut down on the header size for SR as the number of 
geographically enable routers increases.

> I have two concerns with all-geographic techniques:
>
>   1. The Internet is non-euclidean.  Packets almost never follow the
>      as-the-crow-flies shortest path from source to destination, so
>      geographic information is often misleading and suboptimal.

With wireless this is less true no? (because of the range limitations).

>   2. Given the name "www.yahoo.com", how do you obtain the
>      latitude/longitude?  Any sort of system like DNS will introduce a
>      Single Point Of Failure, which is the biggest problem with the
>      Internet today (take out the root servers and the whole internet
>      comes crashing down).

Well ... one challenge at a time ? ;-)

simon

> This is why I lean towards flood filling with geographic "hints".
>
> Also, flood-filling works in tiered networks.  BGP is essentially
> route flooding within the backbone tier (the set of routers with no
> default entry in their routing tables), and it's working today.
>
>   - a
>
>

--
www.simonwoodside.com -- 99% Devil, 1% Angel

_______________________________________________
manet mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/manet

---

From: Daniel Camara <[email-masked]>
Date: Wed, 9 Apr 2003 20:02:27 -0300 (EST)

> geographically enable routers increases.

        First of all, to solve the problem of nodes with out geographic
knowledge, nodes that do not have knowledge of its geographic position can
use other "near" nodes as a proxy and send messages through them. The
header is not necessarily a bad thing if it carries useful information
about other network nodes.  For example, their most updated position. I
agree that the header size is a point to observe, but I think the
information on it can be useful, see:
	Câmara, D., Loureiro A.: A Novel Routing Algorithm for Hoc
	Networks. Baltzer Journal of Telecommunications Systems 18:1-3, 
	Kluwer Academic Publishers(2001) 85-100 

> Well ... one challenge at a time ? ;-)

        In the paper the algorithm uses the packet header to spread the
geographic information, and the routing algorithm uses it in a very simple
way.  The algorithm also observes if the actual node has a better route to
the destination and re-routes the packet if so.

 	The main problem is that the algorithm is based on distance
vector.  So every node has a table with the position of every other node
on the network. In this case each node have at least a guess to which side
the destination node is. Even though this is not scalable for huge
networks it is for sure a start point.

        Best regards ...

	Daniel