[Nml-wg] [Nsi-wg] NML Topology identifiers

[Freek Dijkstra]

On 12-12-2013 12:53, Henrik Thostrup Jensen wrote:

> The reason we made identifiers hierarchial is because we wanted a
> hierarchial model, including the identifiers.

NML allows a hierarchy (using relations), even though it's identifers
are non-hierarchical.

FYI, an earlier attempt was to also make the identifiers hierarchical as
"domain -> node -> port -> link" (See section 8.2 of GFD 202). However
there were some use cases where this didn't apply. For example, NSI
deviated from this hierarchy, only using "domain -> port", and
requesting a "domain -> subdomain" hierarchy. For that reason, NML
clearly chose non-hierarchical identitifiers, and specified that in GFD 202.

If you are saying "we made identifiers hierarchical", which identifiers
do you mean? Do you plan to create a new document describing a different
type of identifiers, possibly using a different prefix?


> I don't care about URNs. They add exactly zero value to the system. I
> have yet to see a good argument for why
> "urn:ogf:network:nordu.net:2013:ps?vlan=1701" is better than
> "nordu.net:ps?vlan=1701"

Prefixes are used to ensure globally uniqueness (and thus prevention of
identifier collisions). It is debatable if that is a real concern or
not. (My personal opinion is not to show the urn:ogf:network" to users
in a GUI, but keep it in the protocol, the few bytes of overhead are not
worth a discussion.)

A secondary use is that it allows easier detection of the type of
identifiers. For example, imagine some like yourself decides that the
current urn:ogf:network identifier syntax is not good. For example cuse
you like to add more hierarchy to it. In that case, it is easy to define
a new prefix (e.g. "urn:ogf:whatever:") and define a better syntax for
those identifiers, and convince the community to start using those
identifiers.

I may not be convinced, but at least that approach would not lead to
incompatible software.

Freek

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