Table 23: MPLS Terms and Acronyms
DefinitionTerm
Accounting mechanism that tracks resource information. Prevents
requests from being accepted if sufficient resources are not available.
Admission control
Border Gateway Protocol, which provides loop-free interdomain
routing between autonomous systems (ASs) and can act as a label
distribution protocol for MPLS.
BGP
An LSR in a point-to-multipoint LSP that is not an ingress node or
an egress node. A branch node can be connected to other branch
nodes, an ingress node, or an egress node.
Branch node
A mechanism to establish paths based on certain criteria (explicit
route, QoS parameters). The standard routing protocols can be
enhanced to carry additional information to be used when running
the route calculation.
Constraint-based routing
EXP-inferred-PSC LSP. The EXP field of the MPLS Shim Header is
used to determine the per-hop behavior applied to the packet.
E-LSP
A subset of constraint-based routing where the constraint is an
explicit route
Explicit routing
Forwarding equivalence class—Group of IP packets forwarded over
the same path with the same path attributes applied
FEC
â–
A particular label distribution protocol used for label distribution
among the routers in an MPLS domain; represented by the
acronym LDP
â–
In lowercase—label distribution protocol—a generic term for
any of several protocols that distribute labels among the routers
in an MPLS domain, including BGP, LDP, and RSVP-TE. This
usage is not represented in this text by the acronym, LDP.
Label Distribution
Protocol
Egress LSRs in a point-to-multipoint LSP. It is also referred as a leaf
node.
Leaf
Label Distribution Protocol—A particular protocol used for label
distribution among the routers in an MPLS domain
This text does not use LDP to refer to the generic class of label
distribution protocols.
LDP
Label edge router—A label-switching router serving as an ingress
or egress nodes
LER
Label-switched path—The path traversed by a packet that is routed
by MPLS. Some LSPs act as tunnels.
LSP
A priority that indicates the importance of one LSP relative to
another LSP. LSPs having higher priorities can preempt LSPs having
lower priorities. Priorities range from 0 through 7 in order of
decreasing priority.
LSP priority level
204 â– MPLS Terms and Acronyms
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