для Cisco Cisco IOS Software Release 12.0(22)S
( D R A F T L A B E L ) A L P H A D R A F T - C I S C O C O N F I D E N T I A L
MPLS Traffic Engineering and Enhancements
Glossary
132
Cisco IOS Release 12.0(22)S
Glossary
affinity—An MPLS traffic engineering tunnel's requirements on the attributes of the links it will cross.
The tunnel's affinity bits and affinity mask bits must match the attribute bits of the various links carrying
the tunnel.
The tunnel's affinity bits and affinity mask bits must match the attribute bits of the various links carrying
the tunnel.
call admission precedence—An MPLS traffic engineering tunnel with a higher priority will, if
necessary, preempt an MPLS traffic engineering tunnel with a lower priority. Tunnels that are harder to
route are expected to have a higher priority and to be able to preempt tunnels that are easier to route. The
assumption is that lower-priority tunnels will be able to find another path.
necessary, preempt an MPLS traffic engineering tunnel with a lower priority. Tunnels that are harder to
route are expected to have a higher priority and to be able to preempt tunnels that are easier to route. The
assumption is that lower-priority tunnels will be able to find another path.
constraint-based routing—Procedures and protocols that determine a route across a backbone take into
account resource requirements and resource availability instead of simply using the shortest path.
account resource requirements and resource availability instead of simply using the shortest path.
flow—A traffic load entering the backbone at one point—point of presence (POP)—and leaving it from
another, that must be traffic engineered across the backbone. The traffic load is carried across one or
more LSP tunnels running from the entry POP to the exit POP.
another, that must be traffic engineered across the backbone. The traffic load is carried across one or
more LSP tunnels running from the entry POP to the exit POP.
head-end—The upstream, transmit end of a tunnel.
IGP—Interior Gateway Protocol. The 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.
ip explicit path—A list of IP addresses, each representing a node or link in the explicit path.
IS-IS—Intermediate System-to-Intermediate System. OSI link-state hierarchical routing protocol that
calls for intermediate system (IS) routers to exchange routing information based on a single metric to
determine network topology.
calls for intermediate system (IS) routers to 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 label-switched path can be chosen dynamically, based on normal
routing mechanisms, or through configuration.
through label switching mechanisms. A label-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, in which label
switching is used to carry the packets.
switching is used to carry the packets.
label switching router (LSR)—A Layer 3 router that forwards packets based on the value of a label
encapsulated in the packets.
encapsulated in the packets.
LCAC—Link-level (per hop) call admission control.
LSA—Link-state advertisement. Flooded packet used by OSPF that contains information about
neighbors and path costs. In IS-IS, receiving routers use LSAs to maintain their routing tables.
neighbors and path costs. In IS-IS, receiving routers use LSAs to maintain their routing tables.
LSP—See label-switched path.
OSPF protocol—Open Shortest Path First. A link state routing protocol used for routing IP.
reoptimization—Reevaluation of the most suitable path for a tunnel to use, given the specified
constraints.
constraints.
RSVP—Resource Reservation Protocol. A protocol for reserving network resources to provide quality
of service guarantees to application flows.
of service guarantees to application flows.
tail-end—The downstream, receive end of a tunnel.
traffic engineering—Techniques and processes that cause routed traffic to travel through the network
on a path other than the one that would have been chosen if standard routing methods were used.
on a path other than the one that would have been chosen if standard routing methods were used.