Cisco Cisco IOS Software Release 12.4(4)T

ARP—Address Resolution Protocol. Internet protocol used to map an IP address to a MAC address. 
Defined in RFC 826. 

ATM—Asynchronous Transfer Mode. The international standard for cell relay in which multiple service 
types (such as voice, video, or data) are conveyed in fixed-length (53-byte) cells. Fixed-length cells 
allow cell processing to occur in hardware, thereby reducing transit delays. ATM is designed to take 
advantage of high-speed transmission media, such as E3, SONET, and T3. 

bundle—A logical grouping of one or more physical interfaces using the formats and procedures of 
multilink Frame Relay. A bundle emulates a physical interface to the Frame Relay data-link layer. The 
bundle is also referred to as the MFR interface.

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

fast switching—Cisco feature in which a route cache expedites packet switching through a router. 

InARP—Inverse Address Resolution Protocol (ARP). Method of building dynamic routes in a network. 
Allows an access server to discover the network address of a device associated with a virtual circuit. 

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. 

MQC—Modular QoS CLI (command line interface). A CLI structure that lets you create traffic polices 
and attach them to interfaces. A traffic policy contains a traffic class and one or more QoS features. A 
traffic class is used to classify traffic, and the QoS features in the traffic policy determine how to treat 
the classified traffic.

PVC—permanent virtual circuit (or connection). Virtual circuit that is permanently established. PVCs 
save bandwidth associated with circuit establishment and teardown in situations where certain virtual 
circuits must exist all the time. In ATM terminology, this is called a permanent virtual connection. 

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

RBE—routed bridge encapsulation. Process by which a stub-bridged segment is terminated on a 
point-to-point routed interface. Specifically, the router is routing on an IEEE 802.3 or Ethernet header 
carried over a point-to-point protocol, such as PPP, RFC 1483 ATM, or RFC 1490 Frame Relay. 

SVC—switched virtual circuit. Virtual circuit that is dynamically established on demand and is torn 
down when transmission is complete. SVCs are used in situations where data transmission is sporadic. 
Called a switched virtual connection in ATM terminology.

ToS—type of service byte. Second byte in the IP header that indicates the desired quality of service for 
a specific datagram. 

VC—virtual circuit. Logical circuit created to ensure reliable communication between two network 
devices. A VC is defined by a VPI/VCI pair and can be either permanent or switched. 

See 

 for terms not included in this glossary.