Glossary

glossary

A

ATM-LSR

An ATM label switching router with a number of LC-ATM interfaces. The router forwards the cells among these interfaces using labels carried in the VPI/VCI field.

A
ATM-LSR	An ATM label switching router with a number of LC-ATM interfaces. The router forwards the cells among these interfaces using labels carried in the VPI/VCI field.

C

CAR

Committed Access Rate (packet classification). CAR is the main feature supporting packet classification. CAR uses the type of service (TOS) bits in the IP header to classify packets. You can use the CAR classification commands to classify and reclassify a packet.

CEF

Cisco Express Forwarding. An advanced Layer 3 IP switching technology. CEF optimizes network performance and scalability for networks with large and dynamic traffic patterns.

CE router

Customer edge router. A router that is part of a customer network and that interfaces to a provider edge (PE) router.

CoS

Class of service. A feature that provides scalable, differentiated types of service across a label switched network.

C
CAR	Committed Access Rate (packet classification). CAR is the main feature supporting packet classification. CAR uses the type of service (TOS) bits in the IP header to classify packets. You can use the CAR classification commands to classify and reclassify a packet.
CEF	Cisco Express Forwarding. An advanced Layer 3 IP switching technology. CEF optimizes network performance and scalability for networks with large and dynamic traffic patterns.
CE router	Customer edge router. A router that is part of a customer network and that interfaces to a provider edge (PE) router.
CoS	Class of service. A feature that provides scalable, differentiated types of service across a label switched network.

D

DWFQ

VIP-Distributed WFQ.

DWRED

VIP-Distributed WRED.

D
DWFQ	VIP-Distributed WFQ.
DWRED	VIP-Distributed WRED.

E

Edge ATM Edge LSR

A router that is connected to the ATM-LSR cloud through LC-ATM interfaces. The edge ATM LSR adds labels to unlabeled packets and removes labels from unlabeled packets.

Edge ATM LSR

A switch router that is connected to the ATM-LSR cloud through LC-ATM interfaces. The edge ATM LSR adds labels to unlabeled packets and strips labels from unlabeled packets.

Edge Label Switch Router (LSR)

The edge device that performs initial packet processing and classification and applies the first label. This device can be either a router, such as the Cisco 7500, or a switch with built-in routing, such as the Cisco BPX 8650.

E
Edge ATM Edge LSR	A router that is connected to the ATM-LSR cloud through LC-ATM interfaces. The edge ATM LSR adds labels to unlabeled packets and removes labels from unlabeled packets.
Edge ATM LSR	A switch router that is connected to the ATM-LSR cloud through LC-ATM interfaces. The edge ATM LSR adds labels to unlabeled packets and strips labels from unlabeled packets.
Edge Label Switch Router (LSR)	The edge device that performs initial packet processing and classification and applies the first label. This device can be either a router, such as the Cisco 7500, or a switch with built-in routing, such as the Cisco BPX 8650.

G

GRE

Generic routing encapsulation. A tunneling protocol developed by Cisco that can encapsulate a wide variety of protocol packet types inside IP tunnels, creating a virtual point-to-point link to Cisco routers at remote points over an IP internetwork. By connecting multiprotocol subnetworks in a single-protocol backbone environment, IP tunneling that uses GRE allows network expansion across a single-protocol backbone environment.

G
GRE	Generic routing encapsulation. A tunneling protocol developed by Cisco that can encapsulate a wide variety of protocol packet types inside IP tunnels, creating a virtual point-to-point link to Cisco routers at remote points over an IP internetwork. By connecting multiprotocol subnetworks in a single-protocol backbone environment, IP tunneling that uses GRE allows network expansion across a single-protocol backbone environment.

I

IGP

Interior Gateway Protocol. An Internet protocol used to exchange routing information within an autonomous system. Examples of common IGPs include IGRP, OSPF, and RIP.

IP Precedence

3-bit value in TOS byte used for assigning Precedence to IP packets.

IS-IS

Intermediate system-to-intermediate system. OSI link-state hierarchical routing protocol in which ISs (routers) exchange routing information based on a single metric in order to determine network topology.

I
IGP	Interior Gateway Protocol. An Internet protocol used to exchange routing information within an autonomous system. Examples of common IGPs include IGRP, OSPF, and RIP.
IP Precedence	3-bit value in TOS byte used for assigning Precedence to IP packets.
IS-IS	Intermediate system-to-intermediate system. OSI link-state hierarchical routing protocol in which ISs (routers) exchange routing information based on a single metric in order to determine network topology.

L

Label

A label is a header used by an LSR to forward packets. The header format depends upon network characteristics. In router networks, the label is a separate, 32-bit header. In ATM networks, the label is placed into the virtual channel identifier/virtual path identifier (VCI/VPI) cell header. In the core, LSRs read only the label, not the packet header. One key to the scalability of MPLS is that labels have only local significance between two devices that are communicating.

Label-Controlled ATM Interface (LC-ATM interface)

An interface on a router or switch that uses label distribution procedures to negotiate label VCs.

Label Distribution Protocol (LDP)

Provides communication between edge and core devices. It assigns labels in edge and core devices to establish Label Switched Paths (LSPs) in conjunction with routing protocols such as OSPF, IS-IS, Enhanced Interior Gateway Routing Protocol (EIGRP), or BGP.

Label Imposition

The act of putting the first label on a packet.

Label-Switched Path (LSP

A sequence of hops (R0...Rn) in which a packet travels from R0 to Rn through MPLS Switching mechanisms. A label-switched path can be established 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 packet.

Label Switch Router (LSR)

The core device that switches labeled packets according to precomputed switching tables. It can also be a switch or a router

Label VC (LVC)

An ATM virtual circuit that is set up through ATM LSR label distribution procedures.

LSA

Link-state advertisement. A broadcast packet used by link-state protocols. The LSA contains information about neighbors and path costs and is used by the receiving router to maintain a routing table.

L
Label	A label is a header used by an LSR to forward packets. The header format depends upon network characteristics. In router networks, the label is a separate, 32-bit header. In ATM networks, the label is placed into the virtual channel identifier/virtual path identifier (VCI/VPI) cell header. In the core, LSRs read only the label, not the packet header. One key to the scalability of MPLS is that labels have only local significance between two devices that are communicating.
Label-Controlled ATM Interface (LC-ATM interface)	An interface on a router or switch that uses label distribution procedures to negotiate label VCs.
Label Distribution Protocol (LDP)	Provides communication between edge and core devices. It assigns labels in edge and core devices to establish Label Switched Paths (LSPs) in conjunction with routing protocols such as OSPF, IS-IS, Enhanced Interior Gateway Routing Protocol (EIGRP), or BGP.
Label Imposition	The act of putting the first label on a packet.
Label-Switched Path (LSP	A sequence of hops (R0...Rn) in which a packet travels from R0 to Rn through MPLS Switching mechanisms. A label-switched path can be established 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 packet.
Label Switch Router (LSR)	The core device that switches labeled packets according to precomputed switching tables. It can also be a switch or a router
Label VC (LVC)	An ATM virtual circuit that is set up through ATM LSR label distribution procedures.
LSA	Link-state advertisement. A broadcast packet used by link-state protocols. The LSA contains information about neighbors and path costs and is used by the receiving router to maintain a routing table.

M

MPLS

Multiprotocol Label Switching. Networks using MPLS, transport IP packets over ATM using label switching, thereby realizing the flexibility and scalability of TCP/IP along with the switching speed and reliability of ATM.

M
MPLS	Multiprotocol Label Switching. Networks using MPLS, transport IP packets over ATM using label switching, thereby realizing the flexibility and scalability of TCP/IP along with the switching speed and reliability of ATM.

N

NLRI

Network layer reachability information. BGP sends routing update messages containing NLRI to describe a route and how to get there. In this context, an NLRI is a prefix. A BGP update message carries one or more NLRI prefixes and the attributes of a route for the NLRI prefixes; the route attributes include a BGP next hop gateway address, community values, and other information.

N
NLRI	Network layer reachability information. BGP sends routing update messages containing NLRI to describe a route and how to get there. In this context, an NLRI is a prefix. A BGP update message carries one or more NLRI prefixes and the attributes of a route for the NLRI prefixes; the route attributes include a BGP next hop gateway address, community values, and other information.

P

PE Router

Provider edge router. A router that is part of a service provider's network and that is connected to a customer edge (CE) router. The PE router function is a combination of an MLS edge label switch router (LSR) function with some additional functions to support VPNs.

P
PE Router	Provider edge router. A router that is part of a service provider's network and that is connected to a customer edge (CE) router. The PE router function is a combination of an MLS edge label switch router (LSR) function with some additional functions to support VPNs.

Q

QoS

Quality of service. Measure of performance for a transmission system that reflects its transmission quality and service availability.

Q
QoS	Quality of service. Measure of performance for a transmission system that reflects its transmission quality and service availability.

R

RED

Random early detection. Congestion avoidance algorithm in which a small percentage of packets are dropped when congestion is detected and before the queue in question overflows completely.

RD

Route distinguisher. An 8-byte value that is concatenated with an IPv4 prefix to create a unique VPN IPv4 prefix.

RIP

Routing Information Protocol. Used to exchange routing information within an autonomous system, RIP uses hop count as a routing metric.

R
RED	Random early detection. Congestion avoidance algorithm in which a small percentage of packets are dropped when congestion is detected and before the queue in question overflows completely.
RD	Route distinguisher. An 8-byte value that is concatenated with an IPv4 prefix to create a unique VPN IPv4 prefix.
RIP	Routing Information Protocol. Used to exchange routing information within an autonomous system, RIP uses hop count as a routing metric.

T

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 used.

Traffic Engineering Tunnel

A label-switched path tunnel that is used for engineering traffic. It is set up through means other than normal Layer 3 routing and is used to direct traffic over a path different from the one that Layer 3 routing would cause it to take.

Tunneling

Architecture providing the services necessary to implement any standard point-to-point data encapsulation scheme.

TOS

Type of Service. A byte in the IPv4 header.

T
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 used.
Traffic Engineering Tunnel	A label-switched path tunnel that is used for engineering traffic. It is set up through means other than normal Layer 3 routing and is used to direct traffic over a path different from the one that Layer 3 routing would cause it to take.
Tunneling	Architecture providing the services necessary to implement any standard point-to-point data encapsulation scheme.
TOS	Type of Service. A byte in the IPv4 header.

V

VPN

Virtual private network. A secure network that shares resources with one or more physical networks. A VPN can contain one or more geographically dispersed sites that can communicate securely over a shared backbone.

VPNV4

Used as a keyword in commands to indicate VPN-IPv4 prefixes. These prefixes are customer VPN addresses, each of which has been made unique by the addition of an 8-byte route distinguisher.

VRF

VPN routing/forwarding instance. A VRF consists of an IP routing table, a derived forwarding table, a set of interfaces that use the forwarding table, and a set of rules and routing protocols that determine what goes into the forwarding table. In general, a VRF includes the routing information that defines a customer VPN site that is attached to a PE router.

V
VPN	Virtual private network. A secure network that shares resources with one or more physical networks. A VPN can contain one or more geographically dispersed sites that can communicate securely over a shared backbone.
VPNV4	Used as a keyword in commands to indicate VPN-IPv4 prefixes. These prefixes are customer VPN addresses, each of which has been made unique by the addition of an 8-byte route distinguisher.
VRF	VPN routing/forwarding instance. A VRF consists of an IP routing table, a derived forwarding table, a set of interfaces that use the forwarding table, and a set of rules and routing protocols that determine what goes into the forwarding table. In general, a VRF includes the routing information that defines a customer VPN site that is attached to a PE router.

W

WEPD

Weighted Early Packet Discard

WFQ

Weighted Fair Queueing. A queue management algorithm that provides a certain fraction of link bandwidth to each of several queues, based on a relative bandwidth applied to each of the queues.

WRED

Weighted RED. A variant of RED in which the probability of a packet being dropped depends on either, its IP Precedence, CAR marking, or Label Switching CoS (as well as the other factors in the RED algorithm).

W
WEPD	Weighted Early Packet Discard
WFQ	Weighted Fair Queueing. A queue management algorithm that provides a certain fraction of link bandwidth to each of several queues, based on a relative bandwidth applied to each of the queues.
WRED	Weighted RED. A variant of RED in which the probability of a packet being dropped depends on either, its IP Precedence, CAR marking, or Label Switching CoS (as well as the other factors in the RED algorithm).

X

xBGP

Border Gateway Protocol. Interdomain routing protocol that exchanges reachability information with other BGP systems. It is defined in RFC 1163.

Table of Contents

glossary