Cisco Cisco IOS Software Release 12.0(15)S
MPLS Traffic Engineering Forwarding Adjacency
Glossary
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Cisco IOS Release 12.0(15)S
Glossary
forwarding adjacency—A traffic engineering link (or LSP) into an IS-IS/OSPF network.
IGP—Interior Gateway Protocol. Internet protocol used to exchange routing information within an
autonomous system. Examples of common IGPs include IGRP, OSPF, and RIP.
autonomous system. Examples of common IGPs include IGRP, OSPF, and RIP.
IS-IS—Intermediate System-to-Intermediate System. OSI link-state hierarchical routing protocol
whereby Intermediate System (IS) routers exchange routing information based on a single metric to
determine network topology.
whereby Intermediate System (IS) routers exchange routing information based on a single metric to
determine network topology.
label-switched path (LSP)—A sequence of hops (R0...Rn) in which a packet travels from R0 to Rn
through label switching mechanisms. A switched path can be chosen dynamically, based on normal
routing mechanisms, or through configuration.
through label switching mechanisms. A switched path can be chosen dynamically, based on normal
routing mechanisms, or through configuration.
label-switched path (LSP) tunnel—A configured connection between two routers, using label
switching to carry the packets.
switching to carry the packets.
MPLS—Multiprotocol label switching (formerly known as tag switching). A method for directing
packets primarily through Layer 2 switching rather than Layer 3 routing. In MPLS, packets are assigned
short fixed-length labels at the ingress to an MPLS cloud by using the concept of forwarding equivalence
classes. Within the MPLS domain, the labels are used to make forwarding decisions mostly without
recourse to the original packet headers.
packets primarily through Layer 2 switching rather than Layer 3 routing. In MPLS, packets are assigned
short fixed-length labels at the ingress to an MPLS cloud by using the concept of forwarding equivalence
classes. Within the MPLS domain, the labels are used to make forwarding decisions mostly without
recourse to the original packet headers.
OSPF—Open Shortest Path First. A link-state routing protocol used for routing.
SPF— Shortest Path First. A routing algorithm used as the basis for OSPF operations. When an SPF
router is powered up, it initializes its routing-protocol data structures and then waits for indications from
lower-layer protocols that its interfaces are functional.
router is powered up, it initializes its routing-protocol data structures and then waits for indications from
lower-layer protocols that its interfaces are functional.
TLV—Type Length Values. Blocks of information embedded in Cisco Discovery Protocol (CDP)
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advertisements.
traffic engineering—The techniques and processes used to cause routed traffic to travel through the
network on a path other than the one that would have been chosen if standard routing methods had been
applied.
network on a path other than the one that would have been chosen if standard routing methods had been
applied.
traffic engineering tunnel—A label-switched tunnel that is used for traffic engineering. Such a tunnel
is set up through means other than normal Layer 3 routing; it is used to direct traffic over a path different
from the one that Layer 3 routing would cause the tunnel to take.
is set up through means other than normal Layer 3 routing; it is used to direct traffic over a path different
from the one that Layer 3 routing would cause the tunnel to take.