[Nsi-wg] Topology virtualisation

[Freek Dijkstra]

John Vollbrecht wrote:

>> [..] A domain of a single link however seems different [..]

> [...] it is important to note that the adjacent network (not
> necessarily a node) enforces the policy of the link.  This could be
> done by having the link delegate policy to the adjacent network or by
> having the adjacent network contact the policy server for the link.
> In the first case policy is run by the adjacent network for the link,
> in the second the adjacent network asks for approval from the link.

This is indeed the crucial question. From an architectural point of
view, the former model is the easiest one, as the requester does not
need to have knowledge about the delegation is done (the requester
directly talks to the owner of the link without worrying how it is
enforced). In the later model, the requester ask one domain for
resources in another domain, and (presumably?) has to be aware of that.

For reasons of simplicity, I prefer the first model. As added advantage
is that this seems very similar to how delegation is done for virtual
networks.

Perhaps related is the question how NSI deals with domains that do not
support NSI yet. This is something to consider -- if we create an
architecture that only works if all domains in the world deploy it at
the same time, then we risk that the deployment takes as long as, say,
IPv6. I wonder if the second model you describe above (where a domain
enforces the policy of a neighbouring domain that does not support NSI)
is applicable to this situation as well.

Regards,
Freek