Mpls - Cisco ONS 15454 DWDM Reference Manual

15.9.1 Overview
network modeling, and performance analysis. Traffic engineering methods include call routing,
connection routing, quality of service (QoS) resource management, routing table management, and
capacity management.
LMP manages TE links between peer nodes, such as two optical cross-connect (OXC) nodes. Peer nodes
have equivalent signaling and routing. LMP also manages TE links between a node such as an OXC and
an adjacent optical line system (OLS) node. An example of an OLS node is an ONS 15454 DWDM node.
Networks with routers, switches, OXC nodes, DWDM OLS nodes, and add/drop multiplexers (ADM)
use a common control plane such as Generalized Multiprotocol Label Switching (GMPLS) to provision
resources and provide network survivability using protection and restoration techniques. LMP is part of
the GMPLS protocol suite.
A single TE link can be formed from several individual links. Management of TE links can be
accomplished with in-band messaging, as well as with out-of-band methods. The following material
describes the LMP between a pair of nodes that manages TE links. LMP accomplishes the following:
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DWDM networks often use Multiprotocol Label Switching (MPLS) and GMPLS as common-control
planes to control how packets are routed through the network.
LMP manages the control channel that must exist between nodes for routing, signaling, and link
management. For a control channel to exist, each node must have an IP interface that is reachable from
the other node. Together, the IP interfaces form a control channel. The interface for the control messages
does not have to be the same interface as the one for the data.

15.9.1.1 MPLS

MPLS provides a mechanism for engineering network traffic patterns that is independent of routing
tables and routing protocols. MPLS assigns short labels to network packets that describe how to forward
the packets through the network. The traditional Layer 3 forwarding mechanism requires each hop to
analyze the packet header and determine the next hop based on routing table lookup. With MPLS, the
analysis of the packet header is performed just once, when a packet enters the MPLS cloud. The packet
is then assigned to a stream known as a Label Switch Path (LSP), which is identified with a label. The
short, fixed-length label is an index into a forwarding table, which is more efficient than the traditional
routing table lookup at each hop. Using MPLS, both the control protocol (used to manage the LSPs) and
user data can be carried over the same bearer interfaces.
15.9.1.2 GMPLS
GMPLS is based on MPLS, with protocol extensions to support additional technologies, including time
division multiplexing (TDM) slots (such as SONET and SDH), wavelength division multiplexing
(WDM) wavelengths at Layer 1, and fiber. For MPLS, the control traffic (signaling and routing) can run
over bearer interfaces. This is not the case with GMPLS, where a separate control channel is used. The
GMPLS control channel is managed with LMP. With GMPLS, the control channels between two
adjacent nodes do not need to use the same physical medium as the data links between those nodes.
Cisco ONS 15454 DWDM Reference Manual, R8.5
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Maintains control channel connectivity
Verifies the physical connectivity of the data links
Correlates the link property information
Suppresses downstream alarms
Localizes link failures for protection/restoration purposes in multiple types of networks
Chapter 15 Management Network Connectivity
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