Subject: RE: Information about optical routing in MPLS net.

From: [email-masked]
Date: Thu, 15 Jun 2000 17:28:16 +0100

I would support the view that having the router control the optical domain
is not good.  This comes down to a simple desire to see an optical layer
which is open to ALL clients - not just IP.  Of course it is possible to
allow the router to control the optical layer ... however, this idea
overlooks the fact that an operator may wish to carry many other clients
across an optical network.

Regards,

Darren Freeland
Networks Analyst
BT Adastral Park

-----Original Message-----
From: George Clapp [mailto:[email-masked]]
Sent: 15 June 2000 17:09
To: Yangguang Xu
Cc: [email-masked]
Subject: Re: Information about optical routing in MPLS net.

At 11:26 AM 6/14/00 -0400, Yangguang Xu wrote:
>Please see comments below:
>
> >
> > a. Considering explicit paths calculation through an optical MPLS
> > network, ingress
> >     routers or third part tools, at the input of the network, will still
> > calculate the
> >     entire path (ingress to egress router), considering links within the
> > optical domain
> >     too?
> >
>
>There have been discussions about this before. My personal opinion is that
>having router control optical domain is not feasible both technically and
>practically.

Could you give some examples of why it's not feasible?

Thanks,
George Clapp
voice     973-829-4610
email     [email-masked]

---

From: Yangguang Xu <[email-masked]>
Date: Thu, 15 Jun 2000 13:29:06 -0400

Following the point from Darren, 

Optical layer is open to ALL clients, e.g. ATM, TDM, SONET/SDH and IP. If you
don't like the client/server model, optical network can also be viewed as a
cloud, which can be tunneled through (please refer to "Hierarchical Tunnel
Establishment in RSVP-TE" discussion). No matter what, optical network try to
achieve true networking rather than simple connectivity or bandwidth. It's as
complicated as pure IP network with many concerns that are unique to optical
domain. Also its protocol will evolve mainly independently from IP (sure will be
affected by IP). So I think IP router should focus more on how to request
service from optical domain than to directly control it.

Yangguang

---

From: Curtis Villamizar <[email-masked]>
Date: Thu, 15 Jun 2000 15:37:27 -0400

In message <[email-masked]
>, [email-masked] writes:
> ... 

Please refer to draft-kompella-mpls-optical-00.txt.

Consider the following example usage.

In the optical core, the optical switches acting as LSR would
advertise the available paths as FSC or LSC tunnels.  The LSR routers
adjacent to the optical core can create PSC over the FSC or LSC
tunnels.  These non-optical LSR will initially (and some people think
always) have no control over the routing of the FSC and LSC tunnels.

If there is a regional distribution of traffic, the core will be
attached to access routers.  This may be using LSC and/or TDM tunnels
again controlled by the optical switches acting as LSR.  The core and
access routers can create PSC to get from the core to the region.

End-to-end tunnels can take 3 hops, one through the near PSC from
access router to core, one through a PSC across the core, and the last
through the PSC across the far region to the destination access
router.

VPN tunnels are signaled via BGP.  These ride inside the e2e tunnels
but as currently implemented use LDP.  This implies that we ween the
VPN tunnels from LDP or do LDP inside the e2e tunnels.  This doesn't
scale as well as just having an RSVP-TE adjacency through the regional
PSC to the core.

Any type of traffic can run through this type of traffic engineered
network within the VPNs.  MPLS-TE provides a means to signal across
multiple optical domains of different type, without requiring all of
the LSR to know anything at all about how to router within any of the
optical domains themselves.

Curtis

ps- I'd be happy to contribute to the usage draft that is being split
out from draft-kompella-mpls-optical-00.txt.