[Nml-wg] More UML....

[Freek Dijkstra]

Aaron Brown wrote:

>> * A _Node_ MUST have a _hasPort_ relation with one or more _Ports_.

> Could we not have an unconnected node?

I concur, and would change it to zero or more Ports.

>> * A _Node_ MAY have a _implementedBy_ relation with one or more _Nodes_.

> Might a node be "implementedBy" a complex topology? E.g. a POP or 
> similar. So you could have a node that is "implementedBy" a network (or 
> whatever it's being called nowadays).

>> A _Port_ is related to zero or one _Node_, and also has a relation 
>> with zero, one or two  (uni-directional) _Links_.
> Where does an unconnected port exist?

>> * A _Port_ MAY have a _source_ relation with up to two _Unidirectional 
>> Links_.

>> * A _Port_ MAY have a _sink_ relation with up to two _Unidirectional 
>> Links_.

> Does this mean that a port might be a sink for two unidirectional links? 
> If so, under what circumstances could it occur that a port could be a 
> sink for more than one link, but not more than two?

>> A _Unidirectional Link_ SHOULD have a _capacity_  attribute which 
>> describes the capacity of the link in bytes per second.

> Not bits per second?

GMPLS defines it in Bytes per second, and I don't see a good reason to 
deviate (although I also wondered why on earth they picked this strange 
convention).

To me it's much more important to be very clear what this attribute 
means. For example, the actual transmission rate of 1 Gbit/s Ethernet is 
1.25*10^9 Baud, which due to the 10b/8b encoding correlates to 1.00*10^9 
bit/s data rate.

In this case, I'd say that the capacity of the physical layer link is 
(1.25*10^9)/8 byte/s and the capacity of the Ethernet layer link is 
(1.00*10^9)/8 byte/s.

>> A Unidirectional Link MUST have an attribute _type_ which is either 
>> _Link_ or _Crossconnect_.

> Would it make sense to make a cross-connect a subclass of link?

That is what we had at first. I think we changed because we sometimes 
want to explicitly say something really is a link, not a cross connect. 
If a cross connect is a subclass of a link, you can not do so.

We briefly played with the notion of having a abstract class called 
"relation", of which both link, cross-connect and adaptation are subclasses.

>> When the type is Link, the source and sink 
>> MUST be of different devices.

This is incorrect -- you may connect two ends of a fiber to the same 
device. Why anyone would want to do that is a different matter, but it 
is possible. The underlying idea is correct though.


Regards,
Freek