Cisco Systems OL-4387-02 manual GL-5

Glossary

T

TCP	Connection-oriented transport layer protocol that provides reliable full-duplex data transmission. TCP
	is part of the TCP/IP protocol stack.

turbo access control A function of the PXF pipeline that determines whether a packet matches a list in a fixed, predictable

listperiod of time, usually regardless of the number of entries in a list. Turbo ACLs enable more expedient packet classification and access checks when the router is evaluating ACLs. The Turbo ACL feature compiles the ACLs into a set of lookup tables, while maintaining the first match requirements. Packet headers are used to access these tables in a small, fixed number of lookups, independently of the existing number of ACL entries.

V

VC	Virtual Circuit. Also referred to as Virtual Channel. Used in ATM applications. A link that seems and
	behaves like a dedicated point-to-point line or a system that delivers packets in sequence, as happens
	on an actual point-to-point network. In reality, the data is delivered across a network via the most
	appropriate route. The sending and receiving devices do not have to be aware of the options and the
	route is chosen only when a message is sent. There is no pre-arrangement, so each virtual circuit exists
	only for the duration of that one transmission.
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 destination of a cell as it passes through a series of ATM switches on its way
	to its destination. ATM switches use the VPI/VCI fields to identify the next network VCL that a cell
	needs to transmit on its way to its final destination. The function of the VCI is similar to that of the
	DLCI in Frame Relay.

VLAN

VPI

Virtual LAN. Group of devices on one or more LANs that are configured (using management software) so that they can communicate as if they were attached to the same wire, when in fact they are located on a number of different LAN segments. Because VLANs are based on logical instead of physical connections, they are extremely flexible.

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 destination of a cell as it passes through a series of ATM switches on its way to its destination. ATM switches use the VPI/VCI fields to identify the next VCL that a cell needs to transmit on its way to its final destination. The function of the VPI is similar to that of the DLCI in Frame Relay.

VRF	Virtual routing and 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.
VSA	Vendor-Specific Attribute. An attribute that has been implemented by a particular vendor. It uses the
	attribute Vendor-Specific to encapsulate the resulting AV pair: essentially, Vendor-Specific =
	protocol:attribute = value.

Cisco 10000 Series Router Service Selection Gateway Configuration Guide

OL-4387-02 GL-5