GMPLS Operation and Deployment Challenges

GMPLS extends MPLS functionality with the enhancement of forwarding, traffic engineering, and quality-of-service (QoS) capabilities of packet-based networks by creating virtual label-switched paths (LSPs) across a network of label switching routers (LSRs) to optical network devices utilizing time-division multiplexing (TDM), fiber switching, and lambda switching. In a GMPLS network it is therefore possible to find and provision end-to-end paths that traverse different networks. For example, a packet/cell-based LSP can be nested in a TDM-based LSP for transport over a SONET network. The TDM-based LSP can similarly be nested in a lambda-based LSP for transport over a wavelength network. Multiple lambda switch-capable LSPs can be nested within a fiber switch-capable set up between two fiber switching elements. This forwarding hierarchy of nested LSPs allows service providers to transparently send different types of traffic over various types of network segments.

GMPLS introduces Link Management Protocol (LMP) to manage and maintain the health of the control and data planes between two neighboring nodes. LMP is an IP-based protocol that includes extensions to the Resource Reservation Protocol Traffic Engineering (RSVP-TE) and Constraint-Based Label Distribution Protocol (CR-LDP) signaling protocols.

GMPLS provides the ability to automate many of the network functions that are directly related to operational complexities, including:

• End-to-end provisioning of services

• Network resource discovery

• Bandwidth assignment

• Service creation

Traffic engineering parameters relating to SONET protection support, available bandwidth, route diversity, and QoS are distributed throughout the network. This allows every node in the network to have full visibility and configuration status of every other node. This ultimately provides an intelligent optical network.

As service providers introduce new network elements into their networks, add or remove facilities, or turn up new circuits, the control plane will automatically distribute and update the network with the new information. Contrast this with the operationally intensive manual upgrades and updates performed today. Provisioning of connections often requires a substantial amount of coordination among operations staff located throughout the network. Capacity is assessed, optimal connection and restoration paths are determined, and the connection must be fully tested after it is established.

In contrast with operationally intensive manual upgrades and updates, GMPLS uses advanced routing features, including the Open Shortest Path First (OSPF) protocol and Intermediate System-to-Intermediate System (IS-IS) protocol and signaling protocols such as RSVP and CR-LDP to build intelligence into the network. The network can then effectively self-discover to dynamically advertise the availability or lack of availability of resources. With such capabilities, multihop connections with optical routes and backup paths can be established in a single provisioning step.
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