[Nsi-wg] Fwd: Thoughts on a basic topology model for NSI

[Evangelos Chaniotakis]

Hey Jeroen,

Your algorithm does not calculate available capacity, then; it's just
reachability. That's not too expensive, but it's also not as useful. :)


On Feb 9, 2010, at 4:00 PM, Jeroen van der Ham wrote:

> On 09/02/2010 15:42, John MacAuley wrote:
>> Jeroen,
>>
>> I agree with the statement that the signal node model would perform  
>> more
>> poorly for optimal path computation, but would the computation of the
>> summarized meshed links not be a costly on an on-going basis? These
>> meshed links would need to be updated anytime there is a reservation
>> added to the network that could impact the availability of the  
>> existing
>> precomputed links. I this model are you providing the summarized
>> bandwidth available between nodes? This would be an extremely costly
>> calculation summing all potential bandwidth.
>
> Yes, there will be a cost in maintaining an up-to-date topology.  
> Again,
> reflecting on the current situation, the time between reservation is
> measured in days, not miliseconds, so this is not really an issue  
> right now.
>
> Then again, if you're doing a single node aggregation, you will be
> getting a lot more false-positives, which means that the clients will
> have to do recalculations.
> I am not sure how the amount of calcalations in the two situations
> balance out. I think that it will fall negatively towards the single
> node aggregation, because each client has to discover false positives
> himself. In the full mesh situation it's calculated once and then  
> shared
> with everyone.
>
>> Do you have description of the mechanism used to compute the meshed
>> topology? I wouldn't mind understanding in more detail if possible.
>
> I think there are several mechanisms to do that.
> The one I used is very simple: for each border node we do a Dijkstra's
> towards all the other border nodes. If there is a path available, then
> we add a link in the full mesh topology. I don't do anything fancy  
> with
> the metric, it's set to 1 on every link.
>
> Jeroen.
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