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Guest Column
GMPLS
– the New Big Deal in Intelligent
Metro Optical Networking
(continued)
Regarding connection set up,
while MPLS requires a Label Switched Path (LSP) between two
end point devices, GMPLS extends this concept beyond simple
point-to-point connections. In a GMPLS network it is possible
to find and provision end-to-end paths that traverse different
networks. For instance, as shown in Figure 1, a packet/cell
LSP can be nested in a TDM LSP for transport over a SONET
network. The TDM LSP can similarly be nested in a Lambda LSP
for transport over a wavelength network. Finally, multiple LSC
LSPs can be nested within a FSC set up between two fiber
switching elements. This forwarding hierarchy of nested LSPs
allows service providers to seamlessly send different types of
traffic over varying network segments.
See
a large view of this graphic
Figure
1. Forwarding Hierarchy of Nested LSPs from
Different Switching-capable Interfaces
GMPLS
also introduces a 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 which includes
extensions to RSVP-TE, CR-LDP signaling protocols. Table 2
summarizes these protocols and the overall extensions for
GMPLS.
|
Protocols
|
Description
|
|
Routing
|
OSPF-TE,
IS-IS-TE
|
See
full-size table |
|
Signaling
|
RSVP-TE,
CR-LDP
|
|
Link
Management |
Link
Management Protocol (LMP)
|
See
full-size table
Table
2. GMPLS Framework
GMPLS-based
Provisioning in Metro Optical Networks
With metro networks becoming
increasingly difficult to operate, GMPLS provides the ability
to automate many of the network functions that are directly
related to the operational complexities. These functions
include end-to-end provisioning of services, network resource
discovery, bandwidth assignment and service creation. Traffic
engineering parameters relating to SONET protection support,
available bandwidth, route diversity and quality of service,
are distributed throughout the network allowing every node in
the network to have full visibility and configuration status
of every other node – ultimately making the optical network
intelligent. Therefore, as service providers introduce new
network elements into their networks, add/remove facilities,
or turn up new circuits, the control plane will automatically
distribute and update the network with the new information.
The contrast today is that many of these upgrades and updates
are performed manually and are operationally intensive.
The complexity of current metro
overlay architectures means the 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 once it is established.
GMPLS, on the other hand, uses advanced routing (OSPF,
IS-IS) and signaling protocols (RSVP, CR-LDP) to build
intelligence into the network such that it is sufficiently
self-discovered to dynamically advertise the availability or
lack of resources throughout the network. With this
capability, multi-hop connections, with optimal routes and
backup paths, can be established in a single provisioning
step.
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