[Nsi-wg] Some topology stuff for Glif

[Henrik Thostrup Jensen]

Hi

On Mon, 30 Sep 2013, Jeroen van der Ham wrote:

> On 30 Sep 2013, at 16:10, Henrik Thostrup Jensen <htj at nordu.net> wrote:
>> There is no bandwdith/capacity attribute in NML. This means we cannot 
>> do capacity matching in pathfinding Is this something we need? (insert 
>> usual disclaimer about advertised bandwidth being different from 
>> avaible)
>
> That should be a good thing for the NSI Extension to add because there 
> it is used in a much stricter context, i.e. service being announced as 
> available (sometimes).

I agree. And this is the obvious way of doing it. However I found that if 
I present a ready solution people start debating and arguing because they 
haven't been heard, so these days I try not to that :-).


>> NML does not have anything to denote available service definitions - 
>> per network or port. This again, makes pathfinding rather tricky and 
>> full of assumptions. While one can match labels with labels used in a 
>> service definition, there might be certain semantics which is not 
>> supported. Is this something we need to add?
>
> What exactly do you mean?

So, how I know a port can can be used in an ETS or EVTS? Sure I 
can maybe infer this somewhat from a VLAN label to EVTS, but there isn't 
anything stating that just because it has a VLAN label it can do EVTS. 
Regular ETS is somewhat more muddy because we currently don't have labels 
for that (but we could come up with one), so here the problem is more 
apparent.

> This is different from the SwitchingService that I described earlier?

I don't think so.

>> There is something to be said for both models, but not really about 
>> having both at the same. The network id in NSI is really redundant. I 
>> talked to to John about this in Madrid, and while he agreed he just 
>> couldn't get himself to remove (and I agree with this, the whole thing 
>> just feels so goddamn clumsy). Right now we essentially have 1½ 
>> topology model. There are some ways
>
> yes ?

Sorry I was on a train when I wrote this, and it was pretty early

What I was thinking about was to enforce a certain way of applying NML 
within NSI, in such a way that NML was shoehorned into the NSI model. 
Essentially a request would be like this:

networkId: nordu.net
localId: ps

this would then map to the port id: urn:ogf:network:nordu.net:ps

This would force the topology id to correspond to the NSI network id. One 
can probably come up with some similar ways for this.

> We're still using a somewhat "simple" topology where we have an explicit 
> split between aggregator NSAs and NSAs taking care of a single network. 
> If we ever move to a different kind of model, you need to have both an 
> identifier for the NSA (i.e. network) and the specific Port that you 
> want to get at.

I think having explicit identifiers for network and NSA is perfectly fine. 
However NML doesn't really have the concept of a network, only a topology.

> And also given that URIs should not be interpreted 
> (according to the RFCs and GFDs), we need to have separate ones.

Yearh that fact has some trouble getting into my head. Especially since a 
lot of rules for how construct them.

What do you call a rule that cannot be enforced in any practical way?

>> Then there are some security aspects. How do I control that no one 
>> injects services / topologies / servies into the topology? In OpenNSA, 
>> I do the following in the configuration:
>
> That makes some sense indeed. We have to look at that more closely if we 
> want to continue this model.

If I cannot interpret URNs, then this verification becomes rather 
impossible. This means that NSAs can (or should) import topologies from 
NSAs which they completely and uttterly thrust not to pollute anything 
(accidently or on purpose). That sucks.


     Best regards, Henrik

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