adding _includeTopology and _excludeTopology path constraints

[carloperocchio]

Questions and answers discussion: Italo Busi, Sergio Belotti, Daniele Ceccarelli, Francesco Lazzeri, Gianmarco Bruno, Carlo Perocchio Monday, December 05, 2016

Q: Which is the usage foreseen for topology-id in path constraints?

R: It is used to include or exclude a give topology. Just one at time.

[italobusi]

Notes from the call on January 12:

The topology-id in path constraints allows constraining the topology the requested path shall belong to.

The _avoidTopology allows constraining which topologies shall be avoided by path computation. This attribute should be changed into a list of topologies.

Need to add also a _includeTopology list to constaints which topologies shall be considered by path computation.

There are some relationships between these attributes: to be further discussed

[italobusi]

@rvilalta : can we start updating the YANG model making the _avoidTopology a list and adding the _includeTopology?

[italobusi]

@carloperocchio : I think this issue should be labelled as "need discussion"

[GianmarcoBruno]

What about renaming _avoidTopology to _excludeTopology as it is more consistent to those familiar with PCEP?

[italobusi]

This is the definition of the topology-id in the ietf-te-types.yang module:

      leaf topology-id {
        type te-types:te-topology-id;
        description
          "The tunnel path is computed using the specific
          topology identified by this identifier";
      }

[tsaad-dev]

topology-id is used as an additional constraint to force the path to be computed in a specific topology

[italobusi]

Call April 13 2017

It seems that the use of the topology-id attribute in TE Tunnel model is not fully clear. Need support from TE Tunnel model authors.

[italobusi]

The topology-id attribute gives context to the references to the topological entities (e.g., node-id, ttp-id, ltp-id) used within the TE Tunnel

[italobusi]

Still needs to discuss whether we need to constraint path computation with _includeTopology and _excludeTopology path constraints

[italobusi]

Pending clarification of the underlying requirement in ONF

It can be added in a future update (even a future RFC) after the requirements is clarified

[italobusi]

Outside the scope of the current document

We may consider this enhancement for a future RFC once the ONF requirement is clarified