affinity bits—An MPLS traffic engineering tunnel’s requirements on the attributes of the links it will cross. The tunnel’s affinity bits and affinity mask must match with the attributes 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. An expected use is that tunnels that are more difficult to route will have a higher priority, and can preempt tunnels that are less difficult to route, on the assumption that those lower priority tunnels can find another path.
constraint-based routing—Procedures and protocols used to determine a route across a backbone taking into 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 will be carried across one or more LSP tunnels running from the entry POP to the exit POP.
headend —The LSR at which the tunnel originates. The tunnel’s “head” or tunnel interface will reside at this LSR as well.
informs —A type of notification message that is more reliable than a conventional trap notification message because an informs message requires acknowledgment.
label —A short, fixed-length data construct that tells switching nodes how to forward data (packets or cells).
label switched path (LSP) tunnel—A configured connection between two routers, using label switching to carry the packets.
LSP —label switched path. A path that is followed by a labeled packet over several hops, starting at an ingress LSR and ending at an egress LSR.
LSR —label switch router. A Layer 3 router that forwards a packet based on the value of a label encapsulated in the packet.
MIB —Management Information Base. A database of network management information (consisting of MIB objects) that is used and maintained by a network management protocol such as SNMP. The value of a MIB object can be changed or retrieved using SNMP commands, usually by a GUI-based network management system. MIB objects are organized in a tree structure that includes public (standard) and private (proprietary) branches.
MPLS —Multiprotocol Label Switching. Switching method that forwards IP traffic using a label. This label instructs the routers and the switches in the network where to forward the packets based on preestablished IP routing information.
NMS —network management station. An NMS is a powerful, well-equipped computer (typically an engineering workstation) that is used by a network administrator to communicate with other devices in the network. An NMS is typically used to manage network resources, gather statistics, and perform a variety of network administration and configuration tasks.
notification —A message sent by an SNMP agent to a network management station, console, or terminal to indicate that a significant event within Cisco IOS software has occurred (see traps).
OSPF —Open Shortest Path First. A link-state routing protocol used for routing IP.
RSVP —Resource Reservation Protocol. Protocol for reserving network resources to provide quality of service (QoS) guarantees to application flows.
SNMP —Simple Network Management Protocol. A network management protocol used almost exclusively in TCP/IP networks. SNMP provides a means to monitor and control network devices, manage configurations, collect statistics, monitor performance, and ensure network security.
tailend —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.
trap —A message sent by an SNMP agent to a network management station, console, or terminal to indicate that a significant event within Cisco IOS software has occurred. Traps (notifications) are less reliable than inform requests, because the receiver of the trap does not send an acknowledgment of receipt; furthermore, the sender of the trap cannot determine if the trap was received (see notification).
VCC —virtual channel connection. A VCC is a logical circuit consisting of VCLs that carries data between two endpoints in an ATM network. Sometimes called a virtual circuit connection.
VCI —virtual channel identifier. A 16-bit field in the header of an ATM cell. The VCI, together with the VPI, is used to identify the next network VCL as the cell passes through a series of ATM switches on its way to its final destination.
VCL —virtual channel link. A VCL is the logical connection that exists between two adjacent switches in an ATM network.
VPI —virtual path identifier. An 8-bit field in the header of an ATM cell. The VPI, together with the VCI, is used to identify the next network VCL as the cell passes through a series of ATM switches on its way to its final destination.