The MPLS WG Archive

[Zhi-Wei Lin <zwlin@lucent.com>]

Hi,

Maybe I can set up a scenario where we can see how these routings work.

Let's take an example where we have a service provider XYZ serving the
NY metro area. Let's also assume that the offered service is the
switched optical service.
Let's also assume that XYZ has several customers such as Citibank,
JPMorgan, Turner Cable, Verizon.

1. Citibank wants to set up a connection between its NYC office and its
Atlanta office. In order to reach Atlanta, service provider XYZ may need
to connect with a secondary (intermediate) service provider ABC for
connectivity. 

2. And let's say Citibank wants to be able to specify the explicit
route. That means the Citibank router doing the path computation needs
to know how the nodes are connected, the resources available at the
node, and probably other information such as the SRGs of these links.
Not only that, but it also needs to know the inner topology (and other)
details of the ABC network to do explicit routing. 

3. This means that if other XYZ and ABC customers want explicit routing,
they would also be provided to them (let's say they are all IP over
optical via the POS or the new GFP mapping). 

==> Given this example, how realistic is it (from both a customer
expectation and carrier expectation) to share the type of information
needed to allow the client router to perform explicit routing? 
==> What about the seemingly need to share information across carriers
into customers?

I think this is not a question of whether the vendors can build this
type of box and the mechanisms to support this (clearly vendors can
build whatever customer want -- the issue is what is the customer
getting for the price), but the question really is:

==> How comfortable are carriers in giving this information out, and how
comfortable are customers (especially financial institutions that may
have qualms about their resource use being visible by other customers)
in sharing their network use with other customers.

Again, I don't think this is a question for vendors, but more for
carriers. Vendors of course can have our own opinions and we can offer
what our customer tell us, but let's allow the carriers to formulate
their opinion first and follow what they have to say instead of simply
hand-waving and say "this is what our customers want".

Zhi





Kireeti Kompella wrote:
> 
> > > Suppose router A wants to get to router B, and wants to take two
> > > different ingress and egress points in the optical domain, X->Y
> > > for the primary LSP, and W->Z for the backup.  A does not require
> > > optical protection for the X->Y path, nor for the W->Z path.  A
> > > *does* require that the X->Y path and the W->Z path do not share
> > > common links.  How is this to be done?
> > >
> > > If A did the full path computation, this is simplicity itself.
> > >
> >       NH=> Kireeti, I don't this can be a general answer.  The request
> > (from whatever the client) is for two phyically disjoint paths between two
> > points A and B.
> 
> Neil, A *is* the client.  And A wants two disjoint paths to B via
> *different ingress points in the OTN*.  This is a very reasonable
> request.
> 
> Also, A doing a full path computation is *not* a general answer.
> It is an illustration of an advantage of the peer model, and of
> routers doing a full path computation across the OTN.  To achieve
> what A wants in an overlay/client/UNI model would require a fair
> amount of work in extending routing/signalling/UNI protocols.
> 
> Kireeti.

-- 
Zhi-Wei Lin
Lucent Technologies                       Tel: +1 732 949 5141
101 Crawfords Corner Rd, Rm 3C-512        Fax: +1 732 949 3210
Holmdel, New Jersey 07733-3030 USA      Email: zwlin@lucent.com