Bala,
Many of the larger service providers have already rolled out MPLS in their
networks to perform IP Traffic Engineering. A very short list includes
UUNET (in Europe), Global Crossing, and British Telecom.
The secondary usage for MPLS is to establish network-based virtual private
network services in which MPLS is used to create tunnels (or closed user
groups) across IP networks. AT&T is already offering a service based on
this approach (IP Enabled Frame Relay). Other service providers are looking
at rolling out MPLS-based VPN services in the next year.
In terms of multi-vendor MPLS deployments, most of the early deployments
have been in Cisco/Juniper environments. As such, RSVP-TE is the protocol
of choice for MPLS Traffic Engineering and label switch path creation.
For additional information, please feel free to visit my web site, the MPLS
Resource Center at www.mplsrc.com. There is a very active discussion list
on MPLS operational issues that you might want to join. We also have an
MPLS FAQ that addresses many of your questions.
irwin