The MPLS WG Archive

["Manfredi, Albert E" <Albert.Manfredi@PHL.Boeing.com>]

Mark.Jones wrote:

> Yakov,
> 
> "...what are the scenario(s) where UNI would be useful?" is an 
> excellent question.  Before I could capture my thoughts on this, I 
> received a better description than I could write from a different 
> discussion list.  That correspondence and one set of comments 
> is below. 
>  In short, the best application for the UNI is a carrier's 
> carrier type 
> application or an OVPN, where the customer has leased a select set of 
> resources with flexibility to change the connectivity of those 
> resources at will.

Agree with this. And here is an example.

A few weeks ago, my daughter is about to go off to school (vet school). I
have to set up her PC to use the school's network. Sitting at home, in this
case about 150 miles away from school, it's no problem. Why? Because I can
layer IP over something else, and make it appear to IP as if I were there.
In this case, it was a modem dial-in over PSTN. It could have been an ATM
UNI setup too. Or some such (tunnel over MPLS?).

To tie this back to the redundant provisioning discussion. Let's say I
wanted redundant data paths from my broadband provider. I had suggested that
using IP "options" and carefully chosen OSPF areas, you could achieve this
without anything else.

I was told, and I agree, that this doesn't guarantee that the data paths
will be separate. Because trunks for the two IP data paths might share the
same cable, or cableway. Of course.

The point is, I'm not sure I understand how you can avoid this situation
OTHER THAN by having the service provider know the physical topology of his
network. How can _any_ UNI/NNI scheme ensure that physical paths of
different routes are far apart, except by someone knowing the physical
structure? I don't see how using just IP "options" is any less effective
than any other method.

Bert
albert.e.manfredi@boeing.com