R

RARP

Reverse Address Resolution Protocol: The protocol within the TCP/ IP stack that maps MAC addresses to IP addresses. See also: ARP.

rate queue

A value, assigned to one or more virtual circuits, that specifies the speed at which an individual virtual circuit will transmit data to the remote end. Every rate queue identifies a segment of the total bandwidth available on an ATM link. The sum of all rate queues should not exceed the total available bandwidth.

RCP

Remote Copy Protocol: A protocol for copying files to or from a file system that resides on a remote server on a network, using TCP to guarantee reliable data delivery.

redistribution

Command used in Cisco routers to inject the paths found from one type of routing protocol into another type of routing protocol.
For example, networks found by RIP can be inserted into an IGRP network.

redundancy

In internetworking, the duplication of connections, devices, or services that can be used as a backup in the event that the primary connections, devices, or services fail.

reload

An event or command that causes Cisco routers to reboot.

repeater

A simple hardware device that moves all packets from one local- area network segment to another by regenerating, retiming, and amplifying the electrical signals.

The main purpose of a repeater is to extend the length of the network transmission medium beyond the normal maximum cable lengths.

RIF

Routing Information Field: In source-route bridging, a header field that defines the path direction of the frame or Token (left to right or right to left). It is also defined as part of a MAC header for source-routed frames, which contains path information. This bit is used in an explorer frame to notify computers that it is on its return path.

ring

Two or more stations connected in a logical circular topology. In this topology, which is the basis for Token Ring, FDDI, and CDDI, information is transferred from station to station in sequence.

ring topology

A network logical topology comprising a series of repeaters that form one closed loop by connecting unidirectional transmission links. Individual stations on the network are connected to the network at a repeater. Physically, ring topologies are generally organized in a closed-loop star. Compare with: bus topology and star topology.

RFP

(Request for Purchase) A document issued by a customer to the network designer who then creates a design document.

RIP

Routing Information Protocol: The most commonly used interior gateway protocol in the Internet. RIP employs hop count as a routing metric. See also: Enhanced IGRP, IGP, OSPF, and hop count.

RMON

Remote Monitoring is a standard monitoring specification that enables various network monitors and console systems to exchange network- monitoring data. RMON provides network administrators with more freedom in selecting network-monitoring probes and consoles with features that meet their particular networking needs.

routed protocol

Routed protocols (such as IP and IPX) are used to transmit user data through an internetwork. By contrast, routing protocols (such as RIP, IGRP, and OSPF) are used to update routing tables between routers.

route summarization

In OSPF and IS-IS, the consolidation of publicized addresses so that a single summary route is advertised to other areas by an area border router.

router

A Network-layer mechanism, either software or hardware, using one or more metrics to decide on the best path to use for transmission of network traffic. Sending packets between networks by routers is based on the information provided on Network layers. Historically, this device has sometimes been called a gateway.

routing

The process of locating a path to the destination host. In large networks, the numerous intermediary destinations a packet might travel before reaching its destination can make routing very complex.

routing domain

Any collection of end systems and intermediate systems that operate under an identical set of administrative rules. Every routing domain contains one or several areas, all individually given a certain area address.

routing loops

Routing algorithms that converge slowly can cause routing loops or network outages whereby routers continue to send updates after a route has gone down.

routing metric

Any value that is used by routing algorithms to determine whether one route is superior to another. Metrics include such information as bandwidth, delay, hop count, path cost, load, MTU, reliability, and communication cost, all of which is stored in routing tables. See also: cost.

routing protocol

Any protocol that defines algorithms to be used for updating routing tables between routers. Examples include IGRP, RIP, and OSPF.

routing table

A table kept in a router or other internetworking mechanism that maintains a record of routes to certain network destinations and the metrics associated with those routes.

RP

Route Processor: Also known as a supervisory processor, a module on Cisco 7000 series routers that holds the CPU, system software, and most of the memory components used in the router.

RSP

Route/Switch Processor: A processor module combining the functions of RP and SP used in Cisco 7500 series routers. See also: RP and SP.

RSVP

(Resource Reservation Protocol) An Internet protocol designed to deliver data on time and in the right order over TCP/IP networks. RSVP is a control and signaling protocol, not a routing protocol, and it works by reserving bandwidth from one end system to another; this reduces the bandwidth available to other users.

RTP

(Real-time Transport Protocol) creates a priority queue on a Frame PVC for a set of RTP packet flows.

RTS

Request To Send: An EIA/TIA-232 control signal requesting permission to transmit data on a communication line.