The "net" IS-IS node attribute is not filled by BGP-LS topo provider

In the OSPF case the link-state node-id includes the field "area=xxx"

There is no such field in the IS-IS case.

The IS-IS link-state route does, however, contain an area ID.

Area IDs have a slightly different meaning in OSPF and ISIS. However:

1) without an area-id we can't support the multi-area case where one L1L2 router subtends multiple L1 areas.

2) if we add this we will also be able to support the multi-process case where there are multiple L1s or L2s on the same router (since each L1 or L2 will have a different area ID).