[Nsi-wg] Topology virtualisation

[Jeroen van der Ham]

On 25/06/2010 15:14, Gigi Karmous-Edwards wrote:
> I agree that the removal of non-GOLEs from the topology graph is an
> alternative to creating a constraint during path computation. I thought
> that the removal from the graph would be easier, similar to removal of
> failed links (due to availability etc ) during crank-back.  Having said
> that, in GIRRA, both technology and policy is taken into account but
> availability is not. This is because we do not collect availability
> information only relatively static  information about the topology,
> therefore reducing complexity and the number or required updates.

Availability is then taken into account using crank-back.

As we discussed before, it remains to be seen whether the number of
updates regarding availability outnumbers the load on the network due to
crank-backs.

> With reference to your other comments about policy: having an open
> policy GOLE makes path computation easier, since the fewer "policy-rich
> " domains one has in the computed path the better. IMHO, an ideal global
> path will consist of only the source and destination domains and the
> rest of the path will consist of policy-free GOLEs. Leaving the policy
> of the path to the two endpoint domains only. Does this make sense?

This will really depend on the user! I would imagine that LHC Tier-x
users do not want to use GOLEs, but instead want to make use of the
LHCnet as much as possible.
I realise that the LHC is an extreme case, but similar cases can be made
for NLR/Internet2, GEANT, GLORIAD and other networks that some but not
all users have access to.

Leaving policy out of the equation like this may make pathfinding a
whole lot simpler, but I'm not sure whether you end up with answers that
you can work with.

> I do realize that this is different than traditional approach and I
> realize that today in our real world,  GOLEs are not all interconnected.
> The above statements are based on an "ideal" network.

Given the examples I made above I'm not sure that we'll ever end up with
anything resembling an "ideal" network as you describe.

Jeroen.