[Olsr-dev] Multipath routing in OLSRD

[Hannes Gredler]

extending the infrastructure and add a strawman (=ECMP routes only)
is perhaps a good idea anyway - later on we can decide what fancy algorithms we can
out on for determining path diversity, loopfreeness  for non ECMP paths etc.

/hannes

Markus Kittenberger wrote:
> I would also suggest you share your ideas about multipath stategies here,..
> because if you just send data to all neighbours that would not send the 
> packets directly back to you, you just multiply the chances to get 
> routing loops on one of your path,..
> i mean, if you take the risk of having more problems, you should have a 
> very good stategy to really gain better significant improves,..
> i mean if 1 or 2 hops later all you packets will go again through the 
> same link, its for sure not worth the risk/effort.
> and if your plan is to send packets on every node to "every" posibble 
> route, you may use quite long, bad routes, and suffer with enourmous 
> packet loss/reordering problems (if you do not gurantee that "same" 
> traffic takes (mostly) same route)
> i don`t want to say, multipath will not work, neither do i know your 
> plans, but first step imho is to solve well some theoretical issues, 
> before starting to hack this feature in,..
> regards Markus
> 
> On Tue, Apr 28, 2009 at 9:58 AM, Henning Rogge <(spam-protected) 
> <mailto:(spam-protected)>> wrote:
> 
>     Am Tuesday 28 April 2009 00:33:36 schrieb Adam Nowak:
>      > Hello,
>      > I'm new to this list, and to all the olsr stuff too. Sorry, if
>     I'm asking
>      > about well known issues. I'm interested in implementing multipath
>      > extension to OLSRd. At first, I'd like to add some alternative
>     routes to
>      > the same destination (route entries which has the same
>     destination but
>      > other next-hops). As I've noticed in the code, there is the entry
>      > "rt_best" which is responsible for selecting best route. I don't
>      > understand, how OLSRd interacts with system routing table in
>      > olsr_update_rib_routes() function, can you help me work it out or
>     give
>      > some advices?
>      > Any help would be appreciated!
>     The main problem you have to solve is how to force your packages to
>     stay on
>     the "secondary" route. You cannot do this "hop by hop" because the
>     next hop
>     will just send your packages to the shortest route again.
> 
>     For efficient multipath you need some "distance" (2 hops or more)
>     between the
>     two routes to prevent collisions between the two paths.
> 
>     Henning
> 
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