radio frequency interface

See RFI.

radio network controller

See RNC.


Remote Authentication Dial-In User Service. An authentication method for validating users who attempt to access the router using telnet.

random early detection

See RED.

rate limiting

See policing.


(Pronounced "are-bock") Regional Bell operating company. Regional telephone companies formed as a result of the divestiture of the Bell System.

RC2, RC4, RC5

RSA codes. A family of proprietary (RSA Data Security, Inc.) encryption schemes often used in Web browsers and servers. These codes use variable-length keys up to 2048 bits.


Relational database management system. A system that presents data in a tabular form, that is a collection of tables consisting of rows and columns, with a means of manipulating the tabular data with relational operators.


Russian-dolls bandwidth allocation model. An allocation model that makes efficient use of bandwidth by allowing the class types to share bandwidth. RDM is defined in the Internet draft draft-ietf-tewg-diff-te-russian-03.txt, Russian Dolls Bandwidth Constraints Model for Diff-Serv-aware MPLS Traffic Engineering.

Real-Time Performance Monitoring

See RPM.

real-time transport protocol

See RTP.


Next hop for a static route that allows all matching packets to be sent to the Routing Engine for processing.

record route object

See RRO.

recursive lookup

Method of consulting the routing table to locate the actual physical next hop for a route when the supplied next hop is not directly connected.


Random early detection. Gradual drop profile for a given class that is used for congestion avoidance. RED tries to anticipate incipient congestion and reacts by dropping a small percentage of packets from the head of the queue to ensure that a queue never actually becomes congested.

refresh reduction

In RSVP, an extension that addresses the problems of scaling, reliability, and latency when Refresh messages are used to cover message loss.

Regional Bell operating company


Register message

PIM message unicast by the first-hop router to the rendezvous point (RP) that contains the multicast packets from the source encapsulated within its data field.

Register Stop message

PIM message sent by the RP to the first-hop router to halt the sending of encapsulated multicast packets.


Next hop for a configured route that drops all matching packets from the network and returns an ICMP message to the source IP address. Also used as an action in a routing policy or firewall filter.

relational database management system


Remote Authentication Dial-In User Service


remote monitoring



JUNOS software command that allows a user to change the name of a routing policy, firewall filter, or any other variable character string defined in the router configuration.

rendezvous point

See RP.

Request for Comments

See RFC.

Request message

RIP message used by a router to ask for all or part of the routing table from a neighbor.


Next hop for a static route that allows the router to perform a recursive lookup to locate the physical next hop for the route.

Resource Reservation Protocol


Response message

RIP message used to advertise routing information into a network.

result cell

JUNOS software data structure generated by the Internet Processor ASIC after performing a forwarding table lookup.

ResvConf message

RSVP message that allows the egress router to receive an explicit confirmation message from a neighbor that its Resv message was received.

ResvErr message

RSVP message indicating that an error has occurred along an established LSP. The message is advertised downstream toward the egress router and it does not remove any RSVP soft state from the network.

ResvTear message

RSVP message indicating that the established LSP and its associated soft state should be removed by the network. The message is advertised upstream toward the ingress router.

reverse-path forwarding

See RPF.

reverse-path multicasting

See RPM.

revert timer

For SONET Automatic Protection Switching (APS), a timer that specifies the amount of time (in seconds) to wait after the working circuit has become functional before making the working circuit active again.

rewrite rules

Set the appropriate class-of-service (CoS) bits in an outgoing packet. This allows the next downstream router to classify the packet into the appropriate service group.


Request for Comments. Internet standard specifications published by the Internet Engineering Task Force (IETF).


Radio frequency interface. Interference from high-frequency electromagnetic waves emanating from electronic devices.


Routing Information Base. A logical data structure used by BGP to store routing information.


Router ID. An IP address used by a router to uniquely identify itself to a routing protocol. This address may or may not be equal to a configured interface address.


Routing Information Protocol. Used in IPv4 networks, a distance-vector interior gateway protocol that makes routing decisions based on hop count.


Routing Information Protocol next generation. Used in IPv6 networks, a distance-vector interior gateway protocol that makes routing decisions based on hop count.


Remote monitoring. A standard MIB that defines current and historical MAC-layer statistics and control objects, allowing you to capture real-time information across the entire network. This allows you to detect, isolate, diagnose, and report potential and actual network problems.


Radio network controller. Manages the radio part of the network in UMTS.

route distinguisher

6-byte value, identifying the VPN, that is prefixed to the IPv4 address to create a unique IPv4 address. The new address is part of the VPN IPv4 address family, which is a BGP address family added as an extension to the BGP protocol. It allows you to configure private addresses within the VPN by preventing any overlap with the private addresses in other VPNs.

route filter

JUNOS software syntax used in a routing policy to match an individual route or a group of routes.

route flapping

Condition of network instability where a route is announced and withdrawn repeatedly, often as the result of an intermittently failing link.

route identifier

IP address of the router from which a BGP, IGP, or OSPF packet originated.

route redistribution

Method of placing learned routes from one protocol into another protocol operating on the same router. The JUNOS software accomplishes this with a routing policy.

route reflection

In BGP, the configuration of a group of routers into a cluster and having one system act as a route reflector, redistributing routes from outside the cluster to all routers in the cluster. Routers in a cluster do not need to be fully meshed.

router ID

See RID.

router-link advertisement

OSPF link-state advertisement flooded throughout a single area by all routers to describe the state and cost of the router's links to the area.

router LSA

OSPF link-state advertisement sent by each router in the network. It describes the local router's connected subnets and their metric values.

router priority

Numerical value assigned to an OPSF or IS-IS interface that is used as the first criterion in electing the designated router or designated intermediate system, respectively.

routing domain

See AS.

Routing Engine

Architectural portion of the router that handles all routing protocol processes, as well as other software processes that control the router's interfaces, some of the chassis components, system management, and user access to the router.

Routing Information Base

See RIB.

Routing Information Protocol

See RIP.

Routing Information Protocol next generation

See RIPng.

routing instance

Collection of routing tables, interfaces, and routing protocol parameters. The set of interfaces belongs to the routing tables, and the routing protocol parameters control the information in the routing tables.

routing matrix

Terabit routing system interconnecting up to four T640 routing nodes to deliver up to 2.56 terabits per second (Tbps) of subscriber switching capacity.

routing protocol daemon

See rpd.

routing table

Common database of routes learned from one or more routing protocols. All routes are maintained by the JUNOS routing protocol process.


Rendezvous point. For PIM-SM, a core router acting as the root of the distribution tree in a shared tree.


JUNOS software routing protocol process (daemon). A user-level background process responsible for starting, managing, and stopping the routing protocols on a Juniper Networks router.


Reverse path forwarding. An algorithm that checks the unicast routing table to determine whether there is a shortest path back to the source address of the incoming multicast packet. Unicast RPF helps determine the source of denial-of-service attacks and rejects packets from unexpected source addresses.


  1. Reverse-path multicasting. Routing algorithm used by Distance Vector Multicast Routing Protocol (DVMRP) to forward multicast traffic.

  3. Real-Time Performance Monitoring. A tool for creating active probes to track and monitor traffic.



Record route object. An RSVP message object that notes the IP address of each router along the path of an LSP.

RSA codes

See RC2, RC4, RC5.


Resource Reservation Protocol. A resource reservation setup protocol designed to interact with integrated services on the Internet.

RSVP Path message

RSVP message sent by the ingress router downstream toward the egress router. It begins the establishment of a soft state database for a particular label-switched path.

RSVP Resv message

RSVP message sent by the egress router upstream toward the ingress router. It completes the establishment of the soft state database for a particular label-switched path.

RSVP signaled LSP

Label-switched path that is dynamically established using RSVP Path and Resv messages.


Real-Time Transport Protocol. An Internet protocol that provides mechanisms for the transmission of real-time data, such as audio, video, or voice over IP networks. Compressed RTP is used for VoIP traffic.


Real-time variable bit rate. For ATM2 intelligent queuing (IQ) interfaces, data that is serviced at a higher priority rate than other VBR data. RTVBR is suitable for carrying packetized video and audio. RTVBR provides better congestion control and latency guarantees than non-real-time VBR.