[Nsi-wg] UvA/TUD topology exchange proposal

[Henrik Thostrup Jensen]

On Thu, 18 Sep 2014, John MacAuley wrote:

> In times like these I always ask myself "What would Jerry say?"  This 
> has helped me quite a bit since he stopped participating in the daily 
> activities of the NSI-WG.  Every time I get too deep into the network 
> technology, I can hear Jerry's voice telling me it is too much detail 
> for what we are trying to achieve in NSI.  I take a step back, and try 
> to remove myself from the nitty gritty details of the specific 
> networking technology.  Something to think about…

So this seems like an argument to encapsulate the behaviour instead of 
describing it.

> I have been thinking about the policy topic quite a bit, and I think we 
> have policy in a number of places:
>
> 1. Within networks as described by Henrik.
> 2. Within services definitions - policies on the defined services we offer.
> 3. Within user requests - we talk about path constraints but these are user specified policy to guide the reservation request (and part of the service definitions).
>
> The good thing is if a policy can be enforced it can be described.

Sure, but it doesn't mean that it can be described with whatever is the 
current fashion in topology description.

What BGP did was to throw away complicated routing protocols and simply 
announce reachabilty (path vectors, which is slighly different from 
distance vectors) over each link. This gives the network admins full 
control over what to announce to other networks, and hence completely 
removes the need to describe policy. If I can tell each of my networks 
what they can reach through my network, possibly with some preference for 
multi-homing, they don't need to know anything else.

Sure, BGP doesn't capture everything and you need agreements about what 
can be re-announced, but this is usually not a problem since network don't 
want to provide transit unless you are handing them money.

I am not saying that BGP is the shining light of all routing/pathfinding 
and we should carbon copy it. But it does represent 40 years of 
networking. So when someone comes up and presents something completely 
different, I'd expect a coule of good reasons.


     Best regards, Henrik

  Henrik Thostrup Jensen <htj at nordu.net>
  Software Developer, NORDUnet