Re: [manet] SMF in Manet and MPR

[Christopher Dearlove <[e-mail]>]

Flooding is done over the VHF interface because the whole point of flooding is to reach everyone. And there might be some routers you can only reach using the VHF interface. If you know that you can always reach someone using only UHF flooding, and you consider that flooding via VHF is a disaster, why is it one of your Manet interfaces? Or if you want one hop transmission but not MPR selection why not set willingness zero (never) on that interface?

> On 22 Mar 2022, at 06:31, Henning Rogge <[e-mail]> wrote:
> 
> On Mon, Mar 21, 2022 at 7:17 PM Christopher Dearlove
> <[e-mail]> wrote:
>> This depends on how you set up your link metrics. Flooding MPRs have
>> the option to use or not use link metrics. But if your interfaces are different
>> enough that you’d rather use multiple hops on a better interface rather
>> than fewer hops on a poorer interface, then you should be using link metrics.
>> If you aren’t, you will have problems. (They probably show up even faster
>> with routing.)
> 
> I don't think metrics can resolve my problem. The problem arises from
> calculating the MPRs just from the 2-hop neighborhood.
> 
> Let me sketch the problem.... imagine you have a Mesh with both VHF
> (slow long range) and UHR (fast short range) radios.
> 
> Now imagine your router R has a neighbor A on VHF, which is two-hop
> reachable on UHF... if A also has a neighbor even further away, A will
> ALWAYS be a MPR, because the neighbor of A is at least three hops away
> over UHV.
> 
> Unicast routes will still flow over the UHF network, but flooding will
> be done over VHF, which is a problem.
> 
>> And so the problem here is with that SMF predates link metrics, and hasn’t
>> been updated. It was even worse when I - and others - tried multicasting
>> by intercepting packets in the stack, wrapping them up as a new OLSR (v1)
>> message type and reinjecting into UDP (OLSR port), plus the reverse at
>> reception. Fun days.
> 
> The OLSR implementation from olsr.org has something like this called
> BMF... it was a disaster. ^^
> 
> Henning Rogge