Glossary

Numerics

1X

First phase of third-generation (3G) mobile wireless technology for CDMA2000

networks.

1XEV

Evolutionary phase of third-generation (3G) CDMA2000 networks, divided into two

phases: 1XEV-DO (data only) and 1XEV-DV (data and voice).

3GPP

Third-generation Partnership Project. Created to expedite the development of open,

globally accepted technical specifications for the Universal Mobile

Telecommunications System (UMTS).

3DES

Triple Data Encryption Standard. A 168-bit encryption algorithm that encrypts data

blocks with three different keys in succession, achieving a higher level of

encryption than is achieved with standard DES, and often implemented with cipher

block chaining (CBC). 3DES is one of the strongest encryption algorithms available

for use in virtual private networks (VPNs). Also called Triple DES.

A

AAL

ATM adaptation layer. A series of protocols enabling various types of traffic,

including voice, data, image, and video, to run over an ATM network.

AAL5 mode

ATM adaption layer 5. One of four AALs recommended by the ITU-T. AAL5 is used

predominantly for the transfer of classical IP over ATM. AAL5 is the least complex of

the current AAL recommendations. It offers low bandwidth overhead and simpler

processing requirements in exchange for reduced bandwidth capacity and

error-recovery capability. It is a Layer 2 circuit transport mode that allows you to

send ATM cells between ATM2 IQ interfaces across a Layer 2 circuit-enabled

network. You use Layer 2 circuit AAL5 transport mode to tunnel a stream of

AAL5-encoded ATM segmentation and reassembly protocol data units (SAR-PDUs)

over an MPLS or IP backbone. See also cell-relay mode , Layer 2 circuits , standard

AAL5 mode , and trunk mode .

access concentrator

Router that acts as a server in a PPPoE session, for example, an E-series router.

access point name

See APN .

active route

Route chosen from all routes in the routing table to reach a destination. Active

routes are installed into the forwarding table.

adaptive services

A set of services or applications that you can configure on an Adaptive Service PIC

(AS PIC). The services and applications include stateful firewall, Network Address

Translation (NAT), intrusion detection services (IDS), Internet Protocol Security

(IPSec), Layer 2 Tunneling Protocol (L2TP), and voice services.

add/drop multiplexer

See ADM .

Address Resolution

See ARP .

Protocol

adjacency

Portion of the local routing information that pertains to the reachability of a single

neighbor over a single circuit or interface.

ADM

Add/drop multiplexer. SONET functionality that allows lower-level signals to be

dropped from a high-speed optical connection.

advanced encryption

See AES.

standard

AES

Advanced Encryption Standard. Defined in FIPS PUB 197. The AES algorithm uses

keys of 128, 192, or 256 bits to encrypt and decrypts data in blocks of 128 bits.

aggregate route

Combination of groups of routes that have common addresses into a single entry in

the routing table.

AH

Authentication header. A component of the IPSec protocol used to verify that the

contents of a packet have not changed, and to validate the identity of the sender.

See also ESP .

Alternate Priority

See APQ .

Queuing

ANSI

American National Standards Institute. The United States’ representative to the ISO.

application-specific

See ASIC .

integrated circuit

APN

Access point name. When mobile stations connect to IP networks over a wireless

network, the GGSN uses the APN to distinguish among the connected IP networks

(known as APN networks). In addition to identifying these connected networks, an

APN is also a configured entity that hosts the wireless sessions, which are called

Packet Data Protocol (PDP) contexts.

APQ

Alternate Priority Queuing. Dequeuing method that has a special queue, similar to

Strict Priority Queuing (SPQ), which is visited only 50 percent of the time. The

packets in the special queue still have a predictable latency, although the upper limit

of the delay is higher than that with SPQ. Since the other configured queues share

the remaining 50 percent of the service time, queue starvation is usually avoided.

See also SPQ .

APS

Automatic Protection Switching. Technology used by SONET ADMs to protect

against circuit faults between the ADM and a router and to protect against failing

routers.

: Glossary

area

1. Routing subdomain that maintains detailed routing information about its own

internal composition as well as routing information that allows it to reach other

routing subdomains. In IS-IS, an area corresponds to a Level 1 subdomain.

2. In IS-IS and OSPF, a set of contiguous networks and hosts within an

autonomous system that have been administratively grouped together.

area border router

Router that belongs to more than one area. Used in OSPF.

ARP

Address Resolution Protocol. Protocol used for mapping IP addresses to MAC

addresses.

AS

Autonomous system. Set of routers under a single technical administration. Each AS

normally uses a single interior gateway protocol (IGP) and metrics to propagate

routing information within the set of routers. Also called a routing domain .

AS boundary router

In OSPF, a router that exchanges routing information with routers in other ASs.

AS external link

OSPF link-state advertisement sent by AS boundary routers to describe external

advertisement

routes that they know. These link-state advertisements are flooded throughout the

AS (except for stub areas).

AS path

In BGP, the route to a destination. The path consists of the AS numbers of all routers

that a packet must go through to reach a destination.

ASIC

Application-specific integrated circuit. Specialized processors that perform specific

functions on the router.

ASM

Adaptive Services Module. On a Juniper Networks M7i router, provides the same

functionality as the AS PIC.

Asynchronous Transfer

See ATM .

Mode

ATM

Asynchronous Transfer Mode. A high-speed multiplexing and switching method

utilizing fixed-length cells of 53 octets to support multiple types of traffic.

atomic

Smallest possible operation. An atomic operation is performed either entirely or not

at all. For example, if machine failure prevents a transaction from completing, the

system is rolled back to the start of the transaction, with no changes taking place.

AUC

Authentication center. Part of the Home Location Register (HLR) in third-generation

(3G) systems; performs computations to verify and authenticate the mobile phone

user.

authentication center

See AUC .

authentication header

See AH .

automatic policing

A policer that allows you to provide strict service guarantees for network traffic.

Such guarantees are especially useful in the context of differentiated services for

traffic engineered LSPs, providing better emulation for ATM wires over an MPLS

network.

Automatic Protection

See APS.

Switching

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JUNOS 7.2 Comprehensive Index and Glossary

autonomous system

See AS .

autonomous system

In OSPF, a router that exchanges routing information with routers in other ASs.

boundary router

autonomous system

OSPF link-state advertisement sent by autonomous system boundary routers to

external link

describe external routes that they know. These link-state advertisements are

advertisement

flooded throughout the autonomous system (except for stub areas).

autonomous system

In BGP, the route to a destination. The path consists of the autonomous system

path

numbers of all the routers a packet must pass through to reach a destination.

B

backbone area

In OSPF, an area that consists of all networks in area ID 0.0.0.0, their attached

routers, and all area border routers.

backplane

See midplane.

backward explicit

See BECN .

congestion notification

bandwidth

Range of transmission frequencies a network can use, expressed as the difference

between the highest and lowest frequencies of a transmission channel. In computer

networks, greater bandwidth indicates a faster data transfer rate capacity.

bandwidth model

In Differentiated-Services-aware traffic engineering, determines the value of the

available bandwidth advertised by the interior gateway protocols (IGPs).

base station controller

See BSC .

base station subsystem

See BSS .

Base Station System

See BSSGP .

GPRS Protocol

base transceiver station

See BTS .

BECN

Backward explicit congestion notification. In a Frame Relay network, a header bit

transmitted by the destination device requesting that the source device send data

more slowly. BECN minimizes the possibility that packets will be discarded when

more packets arrive than can be handled. See also FECN .

Bellcore

Bell Communications Research. A research and development organization created

after the divestiture of the Bell System. It is supported by the regional Bell holding

companies (RBHCs), which own the regional Bell operating companies (RBOCs).

BERT

Bit error rate test. A test that can be run on the following interfaces to determine

whether they are operating properly: E1, E3, T1, T3, and channelized (DS3, OC3,

OC12, STM1) interfaces.

BFD

Bidirectional forwarding detection. A simple hello mechanism that detects failures

in a network. Used with routing protocols to speed up failure detection.

4 „ B

: Glossary

BGP

Border Gateway Protocol. Exterior gateway protocol used to exchange routing

information among routers in different autonomous systems.

bidirectional forwarding

See BFD .

detection

bit error rate test

See BERT .

bit rate

The number of bits transmitted per second.

BITS

Building Integrated Timing Source. Dedicated timing source that synchronizes all

equipment in a particular building.

Blowfish

An unpatented, symmetric cryptographic method developed by Bruce Schneier and

used in many commercial and freeware software applications. Blowfish uses

variable-length keys of up to 448 bits.

BOOTP

Bootstrap protocol. A UDP/IP-based protocol that allows a booting host to configure

itself dynamically and without user supervision. BOOTP provides a means to notify

a host of its assigned IP address, the IP address of a boot server host, and the name

of a file to be loaded into memory and executed. Other configuration information

such as the local subnet mask, the local time offset, the addresses of default routers,

and the addresses of various Internet servers can also be communicated to a host

using BOOTP.

bootstrap protocol

See BOOTP .

Border Gateway

See BGP .

Protocol

BPDU

Bridge protocol data unit. A Spanning Tree Protocol hello packet that is sent out at

intervals to exchange information across bridges to detect loops in a network

topology.

bridge

A device that uses the same communications protocol to connect and pass packets

between two network segments. A bridge operates at Layer 2 of the OSI reference

model.

bridge protocol data

See BPDU.

unit

broadcast

Operation of sending network traffic from one network node to all other network

nodes.

BSC

Base station controller. Key network node in third-generation (3G) systems that

supervises the functioning and control of multiple base transceiver stations.

BSS

Base station subsystem. Composed of the base transceiver station (BTS) and base

station controller (BSC).

BSSGP

Base Station System GPRS Protocol. Processes routing and quality-of-service (QoS)

information for the BSS.

BTS

Base transceiver station. Mobile telephony equipment housed in cabinets and

colocated with antennas. (Also known as a radio base station.)

B „ 5

JUNOS 7.2 Comprehensive Index and Glossary

Building Integrated

See BITS .

Timing Source

bundle

1. Multiple physical links of the same type, such as multiple asynchronous lines, or

physical links of different types, such as leased synchronous lines and dial-up

asynchronous lines.

2. Collection of software that makes up a JUNOS software release.

bypass LSP

Carries traffic for an LSP whose link protected interface has failed. A bypass LSP

uses a different interface and path to reach the same destination.

C

CA

Certificate authority. A trusted third-party organization that creates, enrolls,

validates, and revokes digital certificates. The CA guarantees a user’s identity and

issues public and private keys for message encryption and decryption (coding and

decoding).

CAC

Call admission control. In Differentiated-Services-aware traffic engineering, checks

for adequate bandwidth on the path before the LSP is established. If the bandwidth

is insufficient, the LSP is not established and an error is reported.

CAIDA

Cooperative Association for Internet Data Analysis. An association that provides

tools and analyses promoting the engineering and maintenance of a robust,

scalable Internet infrastructure. One tool, cflowd, allows you to collect an aggregate

of sampled flows and send the aggregate to a specified host that runs the cflowd

application available from CAIDA.

call admission control

See CAC .

Call Detail Record

See CDR .

CAMEL

Customized Applications of Mobile Enhanced Logic. An ETSI standard for GSM

networks that enhances the provision of Intelligent Network services.

carrier-of-carriers VPN

A virtual private network (VPN) service supplied to a network service provider that

is supplying either Internet service or VPN service to an end customer. For a

carrier-of-carriers VPN, the customer's sites are configured within the same

autonomous system (AS).

CB

Control Board. On a T640 routing node, part of the host subsystem that provides

control and monitoring functions for router components.

CBC

Cipher block chaining. A mode of encryption using 64 or 128 bits of fixed-length

blocks where each block of plain text is XORed with the previous cipher text block

before being encrypted. See also XOR.

CBR

Constant bit rate. For ATM1 and ATM2 IQ interfaces, data that is serviced at a

constant, repetitive rate. CBR is used for traffic that does not require the ability to

periodically burst to a higher rate, such as non-packetized voice and audio.

6 „ C

: Glossary

CCC

Circuit cross-connect. A JUNOS software feature that allows you to configure

transparent connections between two circuits, where a circuit can be a Frame Relay

DLCI, an ATM VC, a PPP interface, a Cisco HDLC interface, or an MPLS

label-switched path (LSP).

CDMA

Code Division Multiple Access. Technology for digital transmission of radio signals

between, for example, a mobile telephone and a base transceiver station (BTS).

CDMA2000

Radio transmission and backbone technology for the evolution to third-generation

(3G) mobile networks.

CDR

Call Detail Record. A record containing data (such as origination, termination,

length, and time of day) unique to a specific call.

CE device

Customer edge device. Router or switch in the customer's network that is

connected to a service provider's provider edge (PE) router and participates in a

Layer 3 VPN.

cell relay

A data transmission technology based on the use of small, fixed-size packets (cells)

that can be processed and switched in hardware at high speeds. Cell relay is the

basis for many high-speed network protocols, including ATM and IEEE 802.6.

cell-relay mode

A Layer 2 circuit transport mode that allows you to send ATM cells between ATM2

intelligent queuing (IQ) interfaces over an MPLS core network. You use Layer 2

circuit cell-relay transport mode to tunnel a stream of ATM cells over an MPLS or IP

backbone. See also AAL5 mode , Layer 2 circuits , standard AAL5 mode , and trunk

mode .

certificate authority

See CA.

CFEB

Compact Forwarding Engine Board. In M7i and M10i routers, provides route lookup,

filtering, and switching to the destination port.

cflowd

An application available from CAIDA that allows you to collect an aggregate of

sampled flows and send the aggregate to a specified host that runs the cflowd

application.

CFM

Cubic feet per minute. Measure of air flow in volume per minute.

Challenge Handshake

See CHAP .

Authentication Protocol

channel service unit

See CSU/DSU .

CHAP

Challenge Handshake Authentication Protocol. A protocol that authenticates remote

users. CHAP is a server-driven, three-step authentication mechanism that depends

on a shared secret password that resides on both the server and the client.

CIDR

Classless interdomain routing. A method of specifying Internet addresses in which

you explicitly specify the bits of the address to represent the network address

instead of determining this information from the first octet of the address.

CIP

Connector Interface Panel. On an M160 router, the panel that contains connectors

for the Routing Engines, BITS interfaces, and alarm relay contacts.

cipher block chaining

See CBC.

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JUNOS 7.2 Comprehensive Index and Glossary

circuit cross-connect

See CCC .

class of service

See CoS .

classifier

Method of reading a sequence of bits in a packet header or label and determining

how the packet should be forwarded internally and scheduled (queued) for output.

classless interdomain

See CIDR .

routing

Class Selector code

See CSCP.

point

class type

In Differentiated-Services-aware traffic engineering, a collection of traffic flows that

is treated equivalently in a Differentiated Services domain. A class type maps to a

queue and is much like a class-of-service (CoS) forwarding class in concept. It is also

known as a traffic class.

CLEC

(Pronounced “see-lek”) Competitive local exchange carrier. Company that competes

with the already established local telecommunications business by providing its

own network and switching.

CLEI

Common Language Equipment Identifier. Inventory code used to identify and track

telecommunications equipment.

CLI

Command-line interface. Interface provided for configuring and monitoring the

routing protocol software.

client peer

In a BGP route reflection, a member of a cluster that is not the route reflector. See

also nonclient peer .

CLNP

Connectionless Network Protocol. An ISO-developed protocol for OSI

connectionless network service. CLNP is the OSI equivalent of IP.

cluster

In BGP, a set of routers that have been grouped together. A cluster consists of one

system that acts as a route reflector, along with any number of client peers. The

client peers receive their route information only from the route reflector system.

Routers in a cluster do not need to be fully meshed.

Code Division Multiple

See CDMA .

Access

command-line interface

See CLI .

Common Language

See CLEI .

Equipment Identifier

community

1. In BGP, a group of destinations that share a common property. Community

information is included as one of the path attributes in BGP update messages.

2. In SNMP, an authentication scheme that authorizes SNMP clients based on the

source IP address of incoming SNMP packets, defines which MIB objects are

available, and specifies the operations (read-only or read-write) allowed on

those objects.

Compact Forwarding

See CFEB.

Engine Board

8 „ C

: Glossary

competitive local

See CLEC .

exchange carrier

Complete sequence

See CSNP .

number PDU

confederation

In BGP, a group of systems that appears to external autonomous systems as a single

autonomous system.

Connectionless

See CLNP .

Network Protocol

Connector Interface

See CIP .

Panel

constant bit rate

See CBR .

constrained path

In traffic engineering, a path determined using RSVP signaling and constrained

using CSPF. The Explicit Route Object (ERO) carried in the packets contains the

constrained path information. See also ERO.

Constrained Shortest

See CSPF .

Path First

Control Board

See CB .

Cooperative

See CAIDA.

Association for Internet

Data Analysis

core

Central backbone of the network.

CoS

Class of service. Method of classifying traffic on a packet-by-packet basis using

information in the type-of-service (ToS) byte to provide different service levels to

different traffic.

CPE

Customer premises equipment. Telephone, modem, router, or other service

provider equipment located at a customer site.

craft interface

Mechanisms used by a Communication Workers of America craftsperson to

operate, administer, and maintain equipment or provision data communications.

On a Juniper Networks router, the craft interface allows you to view status and

troubleshooting information and perform system control functions.

Critical Security

See CSP .

Parameters

Crypto Officer

A superuser responsible for the proper operation of a router running JUNOS-FIPS.

CSCP

Class Selector code point. Eight Differentiated Services code point (DSCP) values of

the form 'xxx000' (where x may be '0' or '1'). Defined in RFC 2474.

CSNP

Complete sequence number PDU. Packet that contains a complete list of all the

LSPs in the IS-IS database.

CSP

Critical Security Parameter. Routers running JUNOS-FIPS have CSPs of

cryptographic keys and passwords that must be protected at all times.

C „ 9

JUNOS 7.2 Comprehensive Index and Glossary

CSPF

Constrained Shortest Path First. An MPLS algorithm that has been modified to take

into account specific restrictions when calculating the shortest path across the

network.

CSU/DSU

Channel service unit/data service unit. A channel service unit connects a digital

phone line to a multiplexer or other digital signal device. A data service unit

connects a DTE to a digital phone line.

customer edge device

See CE device .

customer premises

See CPE .

equipment

Customized

See CAMEL .

Applications of Mobile

Enhanced Logic

D

daemon

Background process that performs operations for the system software and

hardware. Daemons normally start when the system software is booted, and run as

long as the software is running. In the JUNOS software, daemons are also referred

to as processes.

damping

Method of reducing the number of update messages sent between BGP peers,

thereby reducing the load on these peers without adversely affecting the route

convergence time for stable routes.

data circuit-terminating

See DCE .

equipment

data-driven multicast

See data-MDT .

distribution tree tunnel

Data Encryption

See DES.

Standard

data-link connection

See DLCI .

identifier

data-MDT

Data-driven multicast distribution tree tunnel. A multicast tunnel created and

deleted based on defined traffic loads and designed to ease loading on the default

MDT tunnel.

data service unit

See CSU/DSU .

data terminal

See DTE .

equipment

dcd

Device control process. A JUNOS software interface process (daemon).

DCE

Data circuit-terminating equipment. An RS-232-C device, typically used for a

modem or printer, or a network access and packet switching node.

10 „ D

: Glossary

DCU

Destination class usage. A means of tracking traffic originating from specific

prefixes on the customer edge router and destined for specific prefixes on the

provider core router, based on the IP source and destination addresses.

DE

Discard-eligible bit. In a Frame Relay network, a header bit notifying devices on the

network that traffic can be dropped during congestion to ensure the delivery of

higher priority traffic.

dead-peer detection

See DPD .

default address

Router address that is used as the source address on unnumbered interfaces.

denial of service

See DoS .

dense

See DWDM .

wavelength-division

multiplexing

DES

Data Encryption Standard. A method for encrypting information using a 56-bit key.

Considered to be a legacy method and insecure for many applications. See also

3DES.

designated router

In OSPF, a router selected by other routers that is responsible for sending link-state

advertisements that describe the network, thereby reducing the amount of network

traffic and the size of the routers’ topological databases.

destination class usage

See DCU .

destination prefix

Number of bits of the network address used for the host portion of a CIDR IP

length

address.

DHCP

Dynamic Host Configuration Protocol. Allocates IP addresses dynamically so that

they can be reused when they are no longer needed.

Differentiated Services

Gives different treatment to traffic based on the experimental (EXP) bits in the

MPLS header. Traffic must be marked appropriately and CoS configured.

Differentiated Services

See DiffServ-aware .

aware

Differentiated-

Type of constraint-based routing that can enforce different bandwidth constraints

Services-

for different classes of traffic. It can also do call admission control (CAC) on each

aware traffic

traffic engineering class when a label-switched path (LSP) is established.

engineering

Differentiated Services

See DSCP.

code point

Differentiated Services

Routers in a network that have Differentiated Services enabled.

domain

Diffie-Hellman

A method of key exchange across a nonsecure environment, such as the Internet.

The Diffie-Hellman algorithm negotiates a session key without sending the key itself

across the network by allowing each party to pick a partial key independently and

send part of it to each other. Each side then calculates a common key value. This is

a symmetrical method and keys are typically used only for a short time, then

discarded and regenerated.

D „ 11

JUNOS 7.2 Comprehensive Index and Glossary

DiffServ

Differentiated Services (based on RFC 2474). DiffServ uses the type-of-service (ToS)

byte to identify different packet flows on a packet-by-packet basis. DiffServ adds a

Class Selector code point (CSCP) and a Differentiated Services code point (DSCP).

DiffServ-aware

Paradigm that gives different treatment to traffic based on the experimental (EXP)

bits in the MPLS label header and allows you to provide multiple classes of service.

digital certificate

Electronic file based on private and public key technology that verifies the identity

of the certificate’s holder to protect data exchanged online. Digital certificates are

issued by a certificate authority (CA).

Dijkstra algorithm

See SPF .

DIMM

Dual inline memory module. A 168-pin memory module that supports 64-bit data

transfer.

direct routes

See interface routes .

discard-eligible bit

See DE .

DLCI

Data-link connection identifier. Identifier for a Frame Relay virtual connection (also

called a logical interface ).

DNS

Domain Name System. A system that stores information about hostnames and

domain names. It provides an IP address for each hostname, and lists the email

exchange servers accepting e-mail address for each domain.

document type

See DTD .

definition

Domain Name System

See DNS .

DoS

Denial of service. System security breach in which network services become

unavailable to users.

DPD

Process that recognizes the loss of the primary IPSec IKE peer and establishes a

secondary IPSec tunnel to a backup peer.

DRAM

Dynamic random access memory. Storage source on the router that can be

accessed quickly by a process.

drop profile

Drop probabilities for different levels of buffer fullness that are used by RED to

determine from which queue to drop packets.

DSCP

Differentiated Services code point or DiffServ code point. Values for a 6-bit field

defined for IPv4 and IPv6 packet headers that can be used to enforce

class-of-service (CoS) distinctions in routers.

DSU

Data service unit. A device used to connect a DTE to a digital phone line. Converts

digital data from a router to voltages and encoding required by the phone line. See

also CSU/DSU .

DTD

Document type definition. Defines the elements and structure of an Extensible

Markup Language (XML) document or data set.

12 „ D

: Glossary

DTE

Data terminal equipment. An RS-232-C interface that a computer uses to exchange

information with a serial device.

DVMRP

Distance Vector Multicast Routing Protocol. Distributed multicast routing protocol

that dynamically generates IP multicast delivery trees using a technique called

reverse-path multicasting (RPM) to forward multicast traffic to downstream

interfaces.

DWDM

Dense wavelength-division multiplexing. Technology that enables data from

different sources to be carried together on an optical fiber, with each signal carried

on its own separate wavelength.

Dynamic Host

See DHCP .

Configuration Protocol

E

early packet discard

See EPD.

EBGP

External BGP. A BGP configuration in which sessions are established between

routers in different autonomous systems (ASs).

ECSA

Exchange Carriers Standards Association. A standards organization created after

the divestiture of the Bell System to represent the interests of interexchange

carriers.

edge router

In MPLS, a router located at the beginning or end of a label-switching tunnel. When

at the beginning of a tunnel, an edge router applies labels to new packets entering

the tunnel. When at the end of a tunnel, the edge router removes labels from

packets exiting the tunnel. See also MPLS .

EGP

Exterior gateway protocol, such as BGP.

egress router

In MPLS, the last router in a label-switched path (LSP). See also ingress router.

EIA-530

A serial interface that employs the EIA-530 standard for the interconnection of DTE

and DCE equipment.

EIA

Electronic Industries Association. A United States trade group that represents

manufacturers of electronics devices and sets standards and specifications.

EIR

Equipment identity register. A mobile network database that contains information

about devices using the network.

electrostatic discharge

See ESD .

EMI

Electromagnetic interference. Any electromagnetic disturbance that interrupts,

obstructs, or otherwise degrades or limits the effective performance of electronics

or electrical equipment.

Encapsulating Security

See ESP .

Payload

end system

In IS-IS, a network entity that sends and receives packets.

E „ 13

JUNOS 7.2 Comprehensive Index and Glossary

EPD

Early packet discard. For ATM2 interfaces only, a limit on the number of transmit

packets that can be queued. Packets that exceed the limit are dropped. See also

queue length .

ERO

Explicit Route Object. An extension to RSVP that allows an RSVP PATH message to

traverse an explicit sequence of routers that is independent of conventional

shortest-path IP routing.

ESD

Electrostatic discharge. Stored static electricity that can damage electronic

equipment and impair electrical circuitry when released.

ESP

Encapsulating Security Payload. A protocol for securing packet flows for IPSec using

encryption, data integrity checks, and sender authentication, which are added as a

header to an IP packet. If an ESP packet is successfully decrypted, and no other

party knows the secret key the peers share, the packet was not wiretapped in

transit. See also AH .

Ethernet

Local area network (LAN) technology used for transporting information from one

location to another formalized in the IEEE standard 802.3. Ethernet uses either

coaxial cable or twisted-pair cable. Transmission speeds for data transfer vary from

the original 10 Mbps, to Fast Ethernet at 100 Mbps, to Gigabit Ethernet at 1000

Mbps.

ETSI

European Telecommunications Standardization Institute. A nonprofit organization

that produces voluntary telecommunications standards used throughout Europe.

European

See ETSI .

Telecommunications

Standardization

Institute

EXP bits

Experimental bits, also known as the class-of-service (CoS) bits, located in each

MPLS label and used to encode the CoS value of a packet as it traverses an LSP.

exclusive or

See XOR.

explicit path

See signaled path .

Explicit Route Object

See ERO .

export

Placing of routes from the routing table into a routing protocol.

Extensible Markup

See XML .

Language

external BGP

See EBGP.

external metric

Cost included in a route when OSPF exports route information from external

autonomous systems. There are two types of external metrics: Type 1 and Type 2.

Type 1 external metrics are equivalent to the link-state metric; that is, the cost of

the route, used in the internal autonomous system. Type 2 external metrics are

greater than the cost of any path internal to the autonomous system.

14 „ E

: Glossary

F

fabric schedulers

Identify a packet as high or low priority based on its forwarding class, and associate

schedulers with the fabric priorities.

Far-end alarm and

See FEAC.

control

fast port

A Fast Ethernet port on a J4300 Services Router, and either a Fast Ethernet port or

DS3 port on a J6300 Services Router. The number of ports applies to enabled and

not installed ports. A two-port Fast Ethernet PIM with one enabled port counts as

one fast port. The same PIM with both ports enabled counts as two fast ports.

fast reroute

Mechanism for automatically rerouting traffic on an LSP if a node or link in an LSP

fails, thus reducing the loss of packets traveling over the LSP.

FBF

Filter-based forwarding. A filter that classifies packets to determine their forwarding

path within a router. FBF is used to redirect traffic for analysis.

FCS

Frame check sequence. A calculation that is added to a frame for error control

purposes. It is used in HDLC, Frame Relay, and other data-link layer protocols.

FDDI

Fiber Distributed Data Interface. A set of ANSI protocols for sending digital data

over fiber optic cable. FDDI networks are token-passing networks, and support data

rates of up to 100 Mbps (100 million bits). FDDI networks are typically used as

backbones for wide-area networks.

FEAC

Far-end alarm and control. A T3 signal used to send alarm or status information

from the far-end terminal back to the near-end terminal and to initiate T3

loopbacks at the far-end terminal from the near-end terminal.

FEB

Forwarding Engine Board. In M5 and M10 routers, provides route lookup, filtering,

and switching to the destination port.

FEC

Forwarding equivalence class. Criteria used to forward a set of packets in an

equivalent fashion. Forwarding equivalence classes are defined in the base LDP

specification and may be extended through the use of additional parameters. FECs

are also represented in other label distribution protocols.

FECN

Forward explicit congestion notification. In a Frame Relay network, a header bit

transmitted by the source device requesting that the destination device slow down

its requests for data. FECN and BECN minimize the possibility that packets will be

discarded when more packets arrive than can be handled. See also BECN .

Federal Information

See FIPS .

Processing Standards

Fiber Distributed Data

See FDDI.

Interface

field-replaceable unit

See FRU .

FIFO

First in, first out.

F „ 15

JUNOS 7.2 Comprehensive Index and Glossary

filter

Process or device that screens packets based on certain characteristics, such as

source address, destination address, or protocol, and forwards or discards packets

that match the filter. Filters are used to control data packets or local packets. See

also packet .

filter-based forwarding

See FBF.

FIPS

Federal Information Processing Standards. Define, among other things, security

levels for computer and networking equipment. FIPS is usually applied to military

environments.

firewall

Security gateway positioned between two different networks, usually between a

trusted network and the Internet. A firewall ensures that all traffic that crosses it

conforms to the organization's security policy. Firewalls track and control

communications, deciding whether to pass, reject, discard, encrypt, or log them.

Firewalls also can be used to secure sensitive portions of a local network.

flap damping

See damping .

flapping

See route flapping .

flash drive

Nonvolatile memory card in Juniper Networks M-series and T-series routing

platforms used for storing a copy of the JUNOS software and the current and most

recent router configurations. It also typically acts as the primary boot device.

Flexible PIC

See FPC .

Concentrator

flow

Stream of routing information and packets that are handled by the Routing Engine

and the Packet Forwarding Engine. The Routing Engine handles the flow of routing

information between the routing protocols and the routing tables and between the

routing tables and the forwarding tables, as well as the flow of local packets from

the router physical interfaces to the Routing Engine. The Packet Forwarding Engine

handles the flow of data packets into and out of the router physical interfaces.

flow collection interface

Interface that combines multiple cflowd records into a compressed ASCII data file

and exports the file to an FTP server for storage and analysis, allowing users to

manipulate the output from traffic monitoring operations.

flow monitoring

Application that monitors the flow of traffic and enables lawful interception of

packets transiting between two routers. Traffic flows can be passively monitored by

an offline router or actively monitored by a router participating in the network.

forward explicit

See FECN .

congestion notification

forwarding classes

Affect the forwarding, scheduling, and marking policies applied to packets as they

transit a routing platform. The forwarding class plus the loss priority define the

per-hop behavior. Also known as ordered aggregates in the IETF’s Differentiated

Services architecture.

Forwarding Engine

See FEB .

Board

forwarding equivalence

See FEC.

class

16 „ F

: Glossary

forwarding information

See forwarding table .

base

forwarding table

JUNOS software forwarding information base. The JUNOS routing protocol process

installs active routes from its routing tables into the Routing Engine forwarding

table. The kernel copies this forwarding table into the Packet Forwarding Engine,

which is responsible for determining which interface transmits the packets.

FPC

Flexible PIC Concentrator. An interface concentrator on which PICs are mounted.

An FPC inserts into a slot in a Juniper Networks router. See also PIC.

fragmentation

In TCP/IP, fragmentation refers to the process of breaking packets into the smallest

maximum size packet data unit (PDU) supported by any of the underlying

networks. In the Open Systems Interconnection (OSI) reference model, this process

is known as segmentation. For JUNOS applications, split Layer 3 packets can then

be encapsulated in MLFR or MLPPP for transport.

frame check sequence

See FCS.

Frame Relay

An efficient replacement for the older X.25 protocol because it does not require

explicit acknowledgment of each frame of data. Frame Relay allows private

networks to reduce costs by using shared facilities between the end-point switches

of a network managed by a Frame Relay service provider. Individual data-link

connection identifiers (DLCIs) are assigned to ensure that each customer receives

only their own traffic.

FRF

Frame Relay Forum. A technical committee that promotes Frame Relay by

negotiating agreements and developing standards.

FRF.15

End-to-end Frame Relay Implementation Agreement. An implementation of MLFR

using multiple virtual connections to aggregate logical bandwidth for end-to-end

Frame Relay. Released by the Frame Relay Forum.

FRF.16

Multilink Frame Relay Implementation Agreement. An implementation of MLFR in

which a single logical connection is provided by multiplexing multiple physical

interfaces for user-to-network interface and network-to-network interface (UNI/NNI)

connections. Released by the Frame Relay Forum.

FRU

Field-replaceable unit. A router component that customers can replace onsite.

G

G-CDR

GGSN call detail record. Collection of charges in ASN.1 format that is eventually

billed to a mobile station user.

Generalized

See GMPLS.

Multiprotocol Label

Switching

generic routing

See GRE .

encapsulation

GGSN

Gateway GPRS support node. A router that serves as a gateway between mobile

networks and packet data networks.

G „ 17

JUNOS 7.2 Comprehensive Index and Glossary

Global System for

See GSM .

Mobile Communications

GMPLS

Generalized Multiprotocol Label Switching. A protocol that extends the functionality

of MPLS to include a wider range of label-switched path (LSP) options for a variety

of network devices.

GMSC

Gateway Mobile Switching Center.

GPRS

General Packet Radio System. A packet-switched service that allows full mobility

and wide-area coverage as information is sent and received across a mobile

network.

graceful restart

Process that allows a router whose control plane is undergoing a restart to continue

to forward traffic while recovering its state from neighboring routers. Without

graceful restart, a control plane restart disrupts any services provided by the router.

graceful switchover

JUNOS software feature that allows a change from the primary device, such as a

Routing Engine, to the backup device without interrupting packet forwarding.

gratuitous ARP

A broadcast request for a router’s own IP address to check if that address is being

used by another node. It is primarily used to detect IP address duplication.

GRE

Generic routing encapsulation. A tunneling protocol that encapsulates a variety of IP

packets to enable data transmission through an IP tunnel. It is used to create a

virtual point-to-point link to routers at remote points in a network.

group

Collection of related BGP peers.

GSM

Global System for Mobile Communications. A second-generation (2G) mobile

wireless networking standard defined by ETSI that uses TDMA technology and

operates in the 900-MHz radio band. See also TDMA .

GTP

GPRS tunneling protocol. A protocol that transports IP packets between an SGSN

and a GGSN.

GTP-C

GGSN tunneling protocol, control. A protocol that allows an SGSN to establish packet

data network access for a mobile station.

GTP-U

GGSN tunneling protocol, user plane. A protocol that carries mobile station user

data packets.

H

Hashed Message

See HMAC .

Authentication Code

hashing

A cryptographic technique that is applied over and over (iteratively) to a message of

arbitrary length that produces a hash “message digest” or “signature” of fixed

length that is appended to the message when sent. In security, used to validate that

the contents of a message have not been altered in transit. The Secure Hash

Algorithm (SHA-1) and Message Digest 5 (MD5) are commonly used hashes. See

SHA-1 and MD5

18 „ H

: Glossary

HDLC

High-level Data Link Control. An International Telecommunication Union (ITU)

standard for a bit-oriented data-link layer protocol on which most other bit-oriented

protocols are based.

HLR

Home Location Register. Database containing information about a subscriber and

the current location of a subscriber’s mobile station.

HMAC

Hashed Message Authentication Code. A mechanism for message authentication

that uses cryptographic hash functions. HMAC can be used with any iterative

cryptographic hash function—for example, MD5 or SHA-1—in combination with a

secret shared key. The cryptographic strength of HMAC depends on the properties

of the underlying hash function. Defined in RFC 2104, HMAC: Keyed-Hashing for

Message Authentication .

hold time

Maximum number of seconds allowed to elapse between the time a BGP system

receives successive keepalive or update messages from a peer.

host module

On an M160 router, provides the routing and system management functions of the

router. Consists of the Routing Engine and Miscellaneous Control Subsystem (MCS).

host subsystem

On a T640 routing node, provides the routing and system management functions of

the router. Consists of a Routing Engine and an adjacent Control Board (CB).

HSCSD

High-Speed Circuit Switched Data. Circuit-switched wireless data transmission for

mobile users, at data rates up to 38.4 Kbps.

I

IANA

Internet Assigned Numbers Authority. A regulatory group that maintains all

assigned and registered Internet numbers, such as IP and multicast addresses. See

also NIC .

IBGP

Internal BGP. A BGP configuration in which sessions are established between

routers in the same autonomous systems (ASs).

ICMP

Internet Control Message Protocol. Used in router discovery, ICMP allows router

advertisements that enable a host to discover addresses of operating routers on the

subnet.

ICMP Router Discovery

See IRDP.

Protocol

IDE

Integrated Drive Electronics. Type of hard disk on the Routing Engine.

IDEA

International Data Encryption Algorithm. An algorithm that uses a 128-bit key and

is one of the methods at the heart of Pretty Good Privacy (PGP). IDEA is patented by

Ascom Tech AG and is popular in Europe.

IDS

Intrusion detection service. A service that inspects all inbound and outbound

network activity and identifies suspicious patterns that may indicate a network or

system attack from someone attempting to break into or compromise a system.

IEC

International Electrotechnical Commission. See ISO .

I „ 19

JUNOS 7.2 Comprehensive Index and Glossary

IEEE

Institute of Electrical and Electronics Engineers. An international professional

society for electrical engineers.

IETF

Internet Engineering Task Force. An international community of network designers,

operators, vendors, and researchers concerned with the evolution of the Internet

architecture and the smooth operation of the Internet.

IGMP

Internet Group Management Protocol. Used with multicast protocols to determine

whether group members are present.

IGP

Interior gateway protocol, such as IS-IS, OSPF, and RIP.

IKE

Internet Key Exchange. Part of IPSec that provides ways to securely negotiate the

shared private keys that the AH and ESP portions of IPSec need to function

properly. IKE employs Diffie-Hellman methods and is optional in IPSec (the shared

keys can be entered manually at the endpoints).

ILMI

Integrated local management interface. A specification developed by the ATM

Forum that incorporates network management capabilities into the ATM

user-to-network interface (UNI) and provides bidirectional exchange of

management information between UNI management entities (UMEs).

IMEI

International Mobile Station Equipment Identity. A unique code used to identify an

individual mobile station to a GSM network.

import

Installation of routes from the routing protocols into a routing table.

IMSI

International Mobile Subscriber Identity. Information that identifies a particular

subscriber to a GSM network.

IMT-2000

International Mobile Telecommunications 2000. Global standard for

third-generation (3G) wireless communications, defined by a set of interdependent

ITU Recommendations. IMT-2000 provides a framework for worldwide wireless

access by linking the diverse systems of terrestrial and/or satellite-based networks.

integrated local

See ILMI.

management interface

Integrated Drive

See IDE.

Electronics

ingress router

In MPLS, the first router in a label-switched path (LSP). See also egress router.

inter-AS routing

Routing of packets among different autonomous systems (ASs). See also EBGP.

intercluster reflection

In a BGP route reflection, the redistribution of routing information by a route

reflector system to all nonclient peers (BGP peers not in the cluster). See also route

reflection .

interface routes

Routes that are in the routing table because an interface has been configured with

an IP address. Also called direct routes .

International Data

See IDEA.

Encryption Algorithm

20 „ I

: Glossary

International Mobile

See IMT-2000 .

Telecommunications-

2000

interprovider VPN

A VPN that provides connectivity between separate autonomous systems (ASs) with

separate border edge routers. It is used by VPN customers who have connections to

several different ISPs, or different connections to the same ISP in different

geographic regions, each of which has a different AS.

intermediate system

In IS-IS, the network entity that sends and receives packets and can also route

packets.

internal BGP

See IBGP.

Internet Key Exchange

See IKE .

Internet Security

See ISAKMP .

Association and Key

Management Protocol

intra-AS routing

Routing of packets within a single autonomous system (AS). See also IBGP.

intrusion detection

See IDS.

service

IP

Internet Protocol. The protocol used for sending data from one point to another on

the Internet.

IP Control Protocol

See IPCP .

IPCP

IP Control Protocol. Protocol that establishes and configures IP over the

Point-to-Point Protocol (PPP).

IPSec

IP Security. A standard way to add security to Internet communications. The secure

aspects of IPSec are usually implemented in three parts: the authentication header

(AH), the Encapsulating Security Payload (ESP), and the Internet Key Exchange

(IKE).

IP Security

See IPSec .

IRDP

ICMP Router Discovery Protocol. A protocol that enables a host to determine the

address of a router that it can use as a default gateway.

ISAKMP

Internet Security Association and Key Management Protocol. A protocol that allows

the receiver of a message to obtain a public key and use digital certificates to

authenticate the sender's identity. ISAKMP is designed to be key exchange

independent; that is, it supports many different key exchanges. See also IKE and

Oakley .

IS-IS

Intermediate System-to-Intermediate System. A link-state, interior gateway routing

protocol for IP networks that also uses the shortest-path-first (SPF) algorithm to

determine routes.

ISO

International Organization for Standardization. A worldwide federation of standards

bodies that promotes international standardization and publishes international

agreements as International Standards.

I „ 21

JUNOS 7.2 Comprehensive Index and Glossary

ISP

Internet service provider. Company that provides access to the Internet and related

services.

ITU-T

International Telecommunication Union Telecommunication Standardization

(formerly known as the CCITT). Group supported by the United Nations that makes

recommendations and coordinates the development of telecommunications

standards for the entire world.

J

jitter

Small random variation introduced into the value of a timer to prevent multiple

timer expirations from becoming synchronized.

K

keepalive message

Messages sent between network devices to inform each other that they are still

active.

kernel forwarding table

See forwarding table .

L

L2TP

Layer 2 Tunneling Protocol. A procedure for secure communication of data across a

Layer 2 network that enables users to establish PPP sessions between tunnel

endpoints. L2TP uses profiles for individual user and group access to ensure secure

communication that is as transparent as possible to both end users and

applications.

label

In MPLS, a 20-bit unsigned integer in the range from 0 through 1,048,575, used to

identify a packet traveling along an LSP.

Label Distribution

See LDP.

Protocol

label-switched path

See LSP .

label switching

See MPLS .

Layer 2 circuits

A collection of transport modes that accept a stream of ATM cells, convert these to

an encapsulated Layer 2 format, then tunnel them over an MPLS or IP backbone,

where a similarly configured routing platform segments these packets back into a

stream of ATM cells, to be forwarded to the virtual circuit configured for the far-end

routing platform. Layer 2 circuits are designed to transport Layer 2 frames between

provider edge (PE) routing platforms across a Label Distribution Protocol

(LDP)-signaled MPLS backbone. See also AAL5 mode , cell-relay mode , standard AAL5

mode , and trunk mode .

Layer 2 Tunneling

See L2TP.

Protocol

22 „ J

: Glossary

Layer 2 VPN

Provides a private network service among a set of customer sites using a service

provider's existing MPLS and IP network. A customer's data is separated from other

data using software rather than hardware. In a Layer 2 VPN, the Layer 3 routing of

customer traffic occurs within the customer's network.

Layer 3 VPN

Provides a private network service among a set of customer sites using a service

provider's existing MPLS and IP network. A customer's routes and data are

separated from other routes and data using software rather than hardware. In a

Layer 3 VPN, the Layer 3 routing of customer traffic occurs within the service

provider's network.

LCC

Line-card chassis. Term used by the JUNOS command-line interface (CLI) to refer to

a T640 routing node in a routing matrix.

LCP

Link Control Protocol. A traffic controller that is used to establish, configure, and

test data-link connections for the Point-to-Point Protocol (PPP).

LDAP

Lightweight Directory Access Protocol. Software protocol used for locating resources

on a public or private network.

LDP

Label Distribution Protocol. A protocol for distributing labels in

non-traffic-engineered applications. LDP allows routers to establish label-switched

paths (LSPs) through a network by mapping network-layer routing information

directly to data-link layer switched paths.

LFI

Link fragmentation and interleaving. For MLFR with PPP traffic or MLPPP with PPP

traffic, reduces excessive delays by fragmenting long packets into smaller packets

and interleaving them with real-time frames. For example, short delay-sensitive

packets, such as packetized voice, can race ahead of larger delay-insensitive

packets, such as common data packets.

limited operational

A term used to describe the restrictions placed on FIPS-certified equipment. See

environment

FIPS.

line-card chassis

See LCC .

link

Communication path between two neighbors. A link is up when communication is

possible between the two end points.

Link Control Protocol

See LCP .

link fragmentation and

See LFI .

interleaving

Link Management

See LMP.

Protocol

link services intelligent

See LSQ.

queuing interfaces

link-state PDU

Packets that contain information about the state of adjacencies to neighboring

systems.

LMP

Link Management Protocol. Part of GMPLS, a protocol used to define a forwarding

adjacency between peers and to maintain and allocate resources on the traffic

engineering links.

L „ 23

JUNOS 7.2 Comprehensive Index and Glossary

load balancing

A process that installs all next-hop destinations for an active route in the forwarding

table. You can use load balancing across multiple paths between routers. The

behavior of load balancing varies according to the version of the Internet Protocol

ASIC in the router. Also called per-packet load balancing .

local preference

Optional BGP path attribute carried in internal BGP update packets that indicates

the degree of preference for an external route.

logical router

Logical routing device that is partitioned from an M-series or T-series routing

platform. Each logical router independently performs a subset of the tasks

performed by the main router and has a unique routing table, interfaces, policies,

and routing instances.

loose

In the context of traffic engineering, a path that can use any route or any number of

other intermediate (transit) points to reach the next address in the path. (Definition

from RFC 791, modified to fit LSPs.)

loss-priority map

Maps the loss priority of incoming packets based on code point values.

lower-speed IQ

E1, N xDS0, and T1 interfaces configured on an IQ-based PIC.

interfaces

LSP

1. Sequence of routers that cooperatively perform MPLS operations for a packet

stream. The first router in an LSP is called the ingress router , and the last router

in the path is called the egress router . An LSP is a point-to-point, half-duplex

connection from the ingress router to the egress router. (The ingress and egress

routers cannot be the same router.)

2. See link-state PDU .

LSQ

Link services intelligent queuing interfaces. Interfaces configured on the AS PIC or

ASM that support MLPPP and MLFR traffic and also fully support JUNOS Class of

Service (CoS) components.

M

MAC

Method authenticity check. Any general method that uses encryption to compute a

digital fingerprint (signature) for the original message. The recipient recomputes the

fingerprint and compares it to the fingerprint sent.

MAM

Maximum allocation bandwidth constraints model. In Differentiated-Services-aware

traffic engineering, a constraint model that divides the available bandwidth

between the different classes. Sharing of bandwidth between the class types is not

allowed.

martian address

Network address about which all information is ignored.

MAS

Mobile network access subsystem. A GSN application subsystem that contains the

access server.

mask

See subnet mask .

maximum allocation

See MAM .

bandwidth constraints

model

24 „ M

: Glossary

MBGP

Multiprotocol Border Gateway Protocol. An extension to BGP that allows you to

connect multicast topologies within and between BGP ASs.

MBone

Multicast Backbone. An interconnected set of subnetworks and routers that support

the delivery of IP multicast traffic. The MBone is a virtual network that is layered on

top of sections of the physical Internet.

MCS

Miscellaneous Control Subsystem. On the M40e and M160 routers, provides control

and monitoring functions for router components and SONET clocking for the router.

MD5

Message Digest 5. A one-way hashing algorithm that produces a 128-bit hash used

for generating message authentication signatures. MD-5 is used in AH and ESP. See

also SHA-1 .

MDRR

Modified Deficit Round Robin. A method for selecting queues to be serviced.

MDT

Multicast distribution tree. The path between the sender (host) and the multicast

group (receiver or listener).

MED

Multiple exit discriminator. An optional BGP path attribute consisting of a metric

value that is used to determine the exit point to a destination when all other factors

in determining the exit point are equal.

mesh

Network topology in which devices are organized in a manageable, segmented

manner with many, often redundant, interconnections between network nodes.

Message Digest 5

See MD5 .

method authenticity

See MAC.

check

MIB

Management Information Base. Definition of an object that can be managed by

SNMP.

midplane

Physically separates front and rear cavities inside the chassis, distributes power

from the power supplies, and transfers packets and signals between router

components, which plug into it.

Miscellaneous Control

See MCS .

Subsystem

MLD

Multicast listener discovery. A protocol that manages the membership of hosts and

routers in multicast groups. IPv6 multicast routers use MLD to learn, for each of

their attached physical networks, which groups have interested listeners.

MLFR

Multilink Frame Relay. Logically ties together individual circuits, creating a bundle.

The logical equivalent of MLPPP, MLFR is used for Frame Relay traffic instead of

PPP traffic. FRF.15 and FRF.16 are two implementations of MLFR.

MLPPP

Multilink Point-to-Point Protocol. Enables you to bundle multiple PPP links into a

single logical link between two network devices to provide an aggregate amount of

bandwidth. The technique is often called bonding or link aggregation. Defined in

RFC 1990. See also PPP .

M „ 25

JUNOS 7.2 Comprehensive Index and Glossary

MMF

Multimode fiber. Optical fiber supporting the propagation of multiple frequencies of

light. MMF is used for relatively short distances because the modes tend to disperse

over longer lengths (called modal dispersion) . For longer distances, single mode

fiber (sometimes called monomode) fiber is used. See also single-mode fiber.

mobile station

A mobile device, such as a cellular phone or a mobile personal digital assistant

(PDA).

MPLS

Multiprotocol Label Switching. Mechanism for engineering network traffic patterns

that functions by assigning to network packets short labels that describe how to

forward them through the network. Also called label switching . See also traffic

engineering .

MPS

Mobile point-to-point control subsystem. A GSN application subsystem that controls

all functionality associated with a particular connection.

MSC

Mobile Switching Center. Provides origination and termination functions to calls

from a mobile station user.

MSDP

Multicast Source Discovery Protocol. A protocol used to connect multicast routing

domains to allow domains to discover multicast sources from other domains. It

typically runs on the same router as the PIM sparse mode rendezvous point (RP).

MSISDN

Mobile Station Integrated Services Digital Network Number. A number that callers

use to reach a mobile services subscriber.

MTBF

Mean time between failures. Measure of hardware component reliability.

MTS

Mobile transport subsystem. A GSN application subsystem that implements all the

protocols used by the GSN.

MTU

Maximum transmission unit. Limit on segment size for a network.

multicast

Operation of sending network traffic from one network node to multiple network

nodes.

multicast distribution

See MDT.

tree

multicast listener

See MLD .

discovery

Multiclass MLPPP

Enables multiple classes of service while using MLPPP. Defined in RFC 2686, The

Multi-Class Extension to Multi-Link PPP .

Multicast Source

See MSDP.

Discovery Protocol

Multiclass LSP

In Differentiated-Services-aware traffic engineering, a multiclass LSP functions like

a standard LSP, but also allows you to reserve bandwidth for multiple class types.

The experimental (EXP) bits of the MPLS header are used to distinguish between

class types.

Multilink Frame Relay

See MLFR.

multimode fiber

See MMF.

26 „ M

: Glossary

multiprotocol BGP

See MBGP .

Multiprotocol Label

See MPLS .

Switching

MVS

Mobile visitor register subsystem.

N

NAT

Network Address Translation. A method of concealing a set of host addresses on a

private network behind a pool of public addresses. It can be used as a security

measure to protect the host addresses from direct targeting in network attacks.

National Institute of

See NIST.

Standards and

Technology

NCP

Network Control Protocol. A traffic controller used to establish and configure

different network layer protocols for the Point-to-Point Protocol (PPP).

neighbor

Adjacent system reachable by traversing a single subnetwork. An immediately

adjacent router. Also called a peer .

NET

Network entity title. Network address defined by the ISO network architecture and

used in CLNS-based networks.

NetBIOS

Network basic input/output system. An application programming interface (API)

used by programs on a LAN. NetBIOS provides a uniform set of commands for

requesting the lower-level services required to manage names, conduct sessions,

and send datagrams between nodes on a network.

Network Address

See NAT.

Translation

network basic

See NetBIOS.

input/output system

Network Control

See NCP .

Protocol

network layer

See NLRI .

reachability information

network link

OSPF link-state advertisement flooded throughout a single area by designated

advertisement

routers to describe all routers attached to the network.

Network Time Protocol

See NTP .

NIC

Network Information Center. Internet authority responsible for assigning

Internet-related numbers, such as IP addresses and autonomous system (AS)

numbers. See also IANA .

NIST

National Institute of Standards and Technology. A nonregulatory U.S. federal agency

whose mission is to develop and promote measurement, standards, and

technology.

N „ 27

JUNOS 7.2 Comprehensive Index and Glossary

NLRI

Network layer reachability information. Information that is carried in BGP packets

and is used by MBGP.

nonclient peer

In a BGP route reflection, a BGP peer that is not a member of a cluster. See also

client peer .

not-so-stubby area

See NSSA.

NSAP

Network service access point. Connection to a network that is identified by a

network address.

n-selector

Last byte of a nonclient peer address.

NSSA

Not-so-stubby area. In OSPF, a type of stub area in which external routes can be

flooded.

NTP

Network Time Protocol. A protocol used to synchronize computer clock times on a

network.

O

Oakley

Key determination protocol based on the Diffie-Hellman algorithm that provides

added security, including authentication. Oakley was the key-exchange algorithm

mandated for use with the initial version of ISAKMP, although various algorithms

can be used. Oakley describes a series of key exchanges called “modes” and details

the services provided by each; for example, Perfect Forward Secrecy for keys,

identity protection, and authentication. See also ISAKMP .

OAM

Operation, Administration, and Maintenance. An ATM Forum specification for

monitoring ATM virtual connections. OAM performs standard loopback, fault

detection and notification, and remote defect identification for each connection,

verifying that the connection is up and the router is operational.

OC

Optical Carrier. In SONET, OC levels indicate the transmission rate of digital signals

on optical fiber.

Operation,

See OAM.

Administration, and

Maintenance

OSI

Open Systems Interconnection. Standard reference model for how messages are

transmitted between two points on a network.

OSPF

Open Shortest Path First. A link-state IGP that makes routing decisions based on the

shortest-path-first (SPF) algorithm (also referred to as the Dijkstra algorithm ).

P

package

Collection of files that make up a JUNOS software component.

packet

Data packets and local packets. Data packets are chunks of data transiting the

router as they are forwarded from the source to a destination. Local packets are

chunks of data that are destined for or sent by the Routing Engine.

28 „ O

: Glossary

Packet Forwarding

Architectural portion of the router that processes packets by forwarding them

Engine

between input and output interfaces.

packet loss priority

See PLP.

PADI

PPPoE Active Discovery Initiation packet. A Point-to-Point Protocol over Ethernet

(PPPoE) initiation packet that is broadcast by the client to start the discovery

process.

PADO

PPPoE Active Discovery Offer packet. A Point-to-Point Protocol over Ethernet

(PPPoE) offer packet that is sent to the client by one or more access concentrators

in reply to a PPPoE Active Discovery Initiation (PADI) packet.

PADR

PPPoE Active Discovery Request packet. A Point-to-Point Protocol over Ethernet

(PPPoE) packet sent by the client to one selected access concentrator to request a

session.

PADS

PPPoE Active Discovery Session-Confirmation packet. A Point-to-Point Protocol over

Ethernet (PPPoE) packet sent by the selected access concentrator to confirm the

session.

PADT

PPPoE Active Discovery Termination packet. A Point-to-Point Protocol over Ethernet

(PPPoE) packet sent by either the client or the access concentrator to terminate a

session.

path attribute

Information about a BGP route, such as the route origin, AS path, and next-hop

router.

PC card

(Previously known as a PCMCIA card.) The removable storage media that ships with

each router that contains a copy of the JUNOS software. The PC card is based on

standards published by the Personal Computer Memory Card International

Association (PCMCIA).

PCI

Peripheral Component Interconnect. Standard, high-speed bus for connecting

computer peripherals. Used on the Routing Engine.

PCMCIA

Personal Computer Memory Card International Association. Industry group that

promotes standards for credit card-size memory or I/O devices.

PDP

Packet data protocol. Network protocol, such as IP, used by packet data networks

connected to a GPRS network.

PDU

Protocol data unit. A packet of data passed across a network. The term implies a

specific layer of the OSI seven-layer model and a specific protocol.

Peripheral Component

See PCI .

Interconnect

PE router

Provider edge router. A router in the service provider's network that is connected to

a customer edge (CE) device and participates in a virtual private network (VPN).

PEC

Policing equivalence classes. In traffic policing, a set of packets that is treated the

same by the packet classifier.

peer

Immediately adjacent router with which a protocol relationship has been

established. Also called a neighbor .

P „ 29

JUNOS 7.2 Comprehensive Index and Glossary

peering

The practice of exchanging Internet traffic with directly connected peers according

to commercial and contractual agreements.

Perfect Forward

See PFS .

Secrecy

PFS

Perfect Forward Secrecy protocol. A condition derived from an encryption system

that changes encryption keys often and ensures that no two sets of keys have any

relation to each other. The advantage of PFS is that if one set of keys is

compromised, only communications using those keys are at risk. An example of a

system that uses PFS is Diffie-Hellman.

PGM

Pragmatic General Multicast. A protocol layer that can be used between the IP layer

and the multicast application on sources, receivers, and routers to add reliability,

scalability, and efficiency to multicast networks.

PGP

Pretty Good Privacy. A strong cryptographic technique invented by Philip

Zimmerman in 1991.

Physical Interface Card

See PIC .

PIC

Physical Interface Card. A network interface-specific card that can be installed on

an FPC in the router.

PIM

Protocol Independent Multicast. A protocol-independent multicast routing protocol.

PIM sparse mode routes to multicast groups that might span wide-area and

interdomain internets. PIM dense mode is a flood-and-prune protocol.

PLMN

Public Land Mobile Network. A telecommunications network for mobile stations.

PLP

Packet loss priority. Used to determine the RED drop profile when queuing a packet.

You can set it by configuring a classifier or policer. The system supports two PLP

designations, low and high.

PLP bit

Packet loss priority bit. Used to identify packets that have experienced congestion

or are from a transmission that exceeded a service provider’s customer service

license agreement. This bit can be used as part of a router’s congestion control

mechanism and can be set by the interface or by a filter.

policing

To apply rate limits on bandwidth and burst size for traffic on a particular interface.

pop

Removal of the last label, by a router, from a packet as it exits an MPLS domain.

PPP

Point-to-Point Protocol. A link-layer protocol that provides multiprotocol

encapsulation. PPP is used for link-layer and network-layer configuration. Provides

a standard method for transporting multiprotocol datagrams over point-to-point

links. Defined in RFC 1661.

PPPoE

Point-to-Point Protocol over Ethernet. Network protocol that encapsulates PPP

frames in Ethernet frames and connects multiple hosts over a simple bridging

access device to a remote access concentrator.

PPPoE Active Discovery

See PADI.

Initiation packet

30 „ P

: Glossary

PPPoE Active Discovery

See PADO.

Offer packet

PPPoE Active Discovery

See PADR.

Request packet

PPPoE Active Discovery

See PADS .

Session-Confirmation

packet

PPPoE Active Discovery

See PADT.

Termination packet

PPPoE over ATM

Point-to-Point Protocol over Ethernet frames in Asynchronous Transfer Mode.

Network protocol that encapsulates Point-to-Point Protocol over Ethernet (PPPoE)

frames in Asynchronous Transfer Mode (ATM) frames for digital subscriber line

(DSL) transmission, and connects multiple hosts over a simple bridging access

device to a remote access concentrator.

Pragmatic General

See PGM.

Multicast

precedence bits

First three bits in the type-of-service (ToS) byte. On a Juniper Networks router, these

bits are used to sort or classify individual packets as they arrive at an interface. The

classification determines the queue to which the packet is directed upon

transmission.

preference

Desirability of a route to become the active route. A route with a lower preference

value is more likely to become the active route. The preference is an arbitrary value

in the range from 0 through 255 that the routing protocol process uses to rank

routes received from different protocols, interfaces, or remote systems.

preferred address

On an interface, the default local address used for packets sourced by the local

router to destinations on the subnet.

Pretty Good Privacy

See PGP.

primary address

On an interface, the address used by default as the local address for broadcast and

multicast packets sourced locally and sent out the interface.

primary interface

Router interface that packets go out on when no interface name is specified and

when the destination address does not imply a particular outgoing interface.

Protocol Independent

See PIM .

Multicast

provider edge router

See PE router .

provider router

Router in the service provider’s network that does not attach to a customer edge

(CE) device.

PSNP

Partial sequence number PDU. A packet that contains only a partial list of the LSPs

in the IS-IS link-state database.

push

Addition of a label or stack of labels, by a router, to a packet as it enters an MPLS

domain.

P „ 31

JUNOS 7.2 Comprehensive Index and Glossary

PVC

Permanent virtual circuit. A software-defined logical connection in a network.

Q

QoS

Quality of service. Performance, such as transmission rates and error rates, of a

communications channel or system.

quality of service

See QoS .

queue

A first-in, first-out (FIFO) number of packets waiting to be forwarded over a router

interface. You can configure the minimum and maximum size of the packet queue,

queue admission policies, and other parameters to manage the flow of packets

through the router.

queue length

For ATM1 interfaces only, a limit on the number of transmit packets that can be

queued. Packets that exceed the limit are dropped. See also EPD .

R

RADIUS

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 .

RBOC

(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.

RDM

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

See RPM .

Monitoring

real-time transport

See RTP .

protocol

RED

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.

remote monitoring

See RMON.

32 „ Q

: Glossary

rendezvous point

See RP .

Resource Reservation

See RSVP .

Protocol

reverse-path forwarding

See RPF.

reverse-path

See RPM.

multicasting

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.

RFC

Request for Comments. Internet standard specifications published by the Internet

Engineering Task Force (IETF).

RFI

Radio frequency interface. Interference from high-frequency electromagnetic waves

emanating from electronic devices.

RIP

Routing Information Protocol. Used in IPv4 networks, a distance-vector interior

gateway protocol that makes routing decisions based on hop count.

RIPng

Routing Information Protocol next generation. Used in IPv6 networks, a

distance-vector interior gateway protocol that makes routing decisions based on

hop count.

RMON

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.

RNC

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

route distinguisher

A 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 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 reflection

In BGP, configuring 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 link

OSPF link-state advertisement flooded throughout a single area by all routers to

advertisement

describe the state and cost of the router’s links to the area.

routing domain

See AS .

R „ 33

JUNOS 7.2 Comprehensive Index and Glossary

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

See RIP.

Protocol

Routing Information

See RIPng.

Protocol next

generation

routing instance

A 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 table

Common database of routes learned from one or more routing protocols. All routes

are maintained by the JUNOS routing protocol process.

RP

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

tree in a shared tree.

rpd

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.

RPF

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.

RPM

1. Reverse-path multicasting. Routing algorithm used by Distance Vector Multicast

Routing Protocol (DVMRP) to forward multicast traffic.

2. Real-Time Performance Monitoring. A tool for creating active probes to track

and monitor traffic.

RSA codes

See RC2, RC4, RC5.

RSVP

Resource Reservation Protocol. A resource reservation setup protocol designed to

interact with integrated services on the Internet.

RTP

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.

RTVBR

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.

34 „ R

: Glossary

S

SA

Security association. An IPSec term that describes an agreement between two

parties about what rules to use for authentication and encryption algorithms, key

exchange mechanisms, and secure communications.

SAP

Session Announcement Protocol. Used with multicast protocols to handle session

conference announcements.

SAR

Segmentation and reassembly. Buffering used with ATM.

SCB

System Control Board. On an M40 router, the part of the Packet Forwarding Engine

that performs route lookups, monitors system components, and controls FPC

resets.

SCC

Switch-card chassis. Term used by the JUNOS command-line interface (CLI) to refer

to the TX Matrix platform in a routing matrix.

SCG

SONET Clock Generator. On a T640 routing node, provides the Stratum 3 clock

signal for the SONET/SDH interfaces. Also provides external clock inputs.

scheduler maps

In class of service, associate schedulers with forwarding classes. See also schedulers

and forwarding classes .

schedulers

Define the priority, bandwidth, delay buffer size, rate control status, and RED drop

profiles to be applied to a particular forwarding class for packet transmission. See

also scheduler maps .

SCU

Source class usage. A means of tracking traffic originating from specific prefixes on

the provider core router and destined for specific prefixes on the customer edge

router, based on the IP source and destination addresses.

SDH

Synchronous Digital Hierarchy. A CCITT variation of the SONET standard.

SDP

Session Description Protocol. Used with multicast protocols to handle session

conference announcements.

SDRAM

Synchronous dynamic random access memory.

Secure Hash Algorithm

See SHA-1 .

secure shell

See SSH .

security association

See SA .

Security Parameter

See SPI .

Index

Session Initiation

See SIP .

Protocol

SFM

Switching and Forwarding Module. On an M160 router, a component of the Packet

Forwarding Engine that provides route lookup, filtering, and switching to FPCs.

S „ 35

JUNOS 7.2 Comprehensive Index and Glossary

SFP

Small form-factor pluggable transceiver. Optical transceivers that provide support

for SX, LX, and LH optics, and can be removed from a PIC. SFPs are hot-insertable

and hot-removable.

SGSN

Serving GPRS Support Node. Device in the mobile network that requests PDP

contexts with a GGSN.

SHA-1

Secure Hash Algorithm 1. A secure hash algorithm standard defined in FIPS PUB

180-1 (SHA-1). Developed by the National Institute of Standard Technology (NIST),

SHA-1 (which effectively replaces SHA-0) produces a 160-bit hash for message

authentication. Longer-hash variants include SHA-224, SHA-256, SHA-384, and

SHA-512 (sometimes grouped under the name “SHA-2”). SHA-1 is more secure than

MD5.

shaping rate

In class of service, controls the maximum rate of traffic transmitted on an interface.

See also traffic shaping .

short message service

See SMS.

shortest path first

See SPF .

shortest-path tree

See SPT.

SIB

Switch Interface Board. On a T640 routing node, provides the switching function to

the destination Packet Forwarding Engine.

signaled path

In traffic engineering, an explicit path; that is, a path determined using RSVP

signaling. The ERO carried in the packets contains the explicit path information.

simplex interface

Interface that assumes that packets it receives from itself are the result of a software

loopback process. The interface does not consider these packets when determining

whether the interface is functional.

single-mode fiber

Optical fiber designed for transmission of a single ray or mode of light as a carrier

and is used for long-distance signal transmission. For short distances, multimode

fiber is used. See also MMF.

SIP

Session Initiation Protocol. An Adaptive Services application protocol option used

for setting up sessions between endpoints on the Internet. Examples includes

telephony, fax, videoconferencing, file exchange, and person-to-person sessions.

small form-factor

See SFM .

pluggable transceiver

SMS

Short message service. A GSM service that enables short text messages to be sent to

and from mobile telephones.

SNMP

Simple Network Management Protocol. A protocol governing network management

and the monitoring of network devices and their functions.

SONET

Synchronous Optical Network. A high-speed (up to 2.5 Gbps) synchronous network

specification developed by Bellcore and designed to run on optical fiber. STS-1 is the

basic building block of SONET. Approved as an international standard in 1988. See

also SDH.

source class usage

See SCU .

36 „ S

: Glossary

source-specific

See SSM.

multicast

SPF

Shortest path first. An algorithm used by IS-IS and OSPF to make routing decisions

based on the state of network links. Also called the Dijkstra algorithm .

SPI

Security Parameter Index. In IPSec, a numeric identifier used with the destination

address and security protocol to identify an SA. When IKE is used to establish an

SA, the SPI is randomly derived. When manual configuration is used for an SA, the

SPI must be entered as a parameter.

SPQ

Strict Priority Queuing. A dequeuing method that provides a special queue that is

serviced until it is empty. The traffic sent to this queue tends to maintain a lower

latency and more consistent latency numbers than traffic sent to other queues. See

also APQ .

SPT

Shortest-path tree. An algorithm that builds a network topology that attempts to

minimize the path from one router (the root) to other routers in a routing area.

src port

TCP or UDP port for the source IP address in a packet.

SS7

Signaling System 7. A protocol used in telecommunications for delivering calls and

services.

SSB

System and Switch Board. On an M20 router, a Packet Forwarding Engine

component that performs route lookups and component monitoring and monitors

FPC operation.

SSH

Secure shell. An application that uses strong authentication and encryption for

remote access across a nonsecure network. SSH provides remote login, remote

program execution, file copy, and other functions. In a UNIX environment, SSH is

intended as a secure replacement for rlogin, rsh, and rcp.

SSH/TLS

Secure shell with Transport Layer Security. A combination of two standard methods

used to secure communications over the Internet. TLS is the name of a standard

protocol based on SSL 3.0 and is defined in RFC 2246. In combination, SSH/TLS is

also known as SSHv2 and uses FIPS-restricted cipher sets in a FIPS environment.

SSL

Secure sockets layer. A protocol that encrypts security information using

public-private key technology, which requires a paired private key and

authentication certificate, before transmitting data across a network.

SSM

Source-specific multicast. A service that allows a client to receive multicast traffic

directly from the source. Typically, SSM uses a subset of the PIM sparse-mode

functionality along with a subset of IGMPv3 to create a shortest-path tree between

the client and the source, but builds the shortest-path tree without the help of a

rendezvous point.

SSRAM

Synchronous Static Random Access Memory. Used for storing routing tables, packet

pointers, and other data such as route lookups, policier counters, and other statistics

to which the microprocessor needs quick access.

standard AAL5 mode

A transport mode that allows multiple applications to tunnel the protocol data units

of their Layer 2 protocols over an ATM virtual circuit. You use this transport mode to

tunnel IP packets over an ATM backbone. See also AAL5 mode , cell-relay mode , Layer

2 circuits , and trunk mode .

S „ 37

JUNOS 7.2 Comprehensive Index and Glossary

stateful firewall

A type of firewall filter that evaluates the context of connections, permits or denies

traffic based on the context, and updates this information dynamically. Context

includes IP source and destination addresses, port numbers, TCP sequencing

information, and TCP connection flags. The context received in the first packet of a

TCP session must match the context contained in all subsequent packets if a

session is to remain active.

static LSP

See static path .

static path

In the context of traffic engineering, a static route that requires hop-by-hop manual

configuration. No signaling is used to create or maintain the path. Also called a

static LSP .

static route

An explicitly configured route that is entered into the routing table. Static routes

have precedence over routes chosen by dynamic routing protocols.

STM

Synchronous transport module. CCITT specification for SONET at 155.52 Mbps.

strict

In the context of traffic engineering, a route that must go directly to the next

address in the path. (Definition from RFC 791, modified to fit LSPs.)

STS

Synchronous transport signal. Synchronous transport signal level 1 is the basic

building block signal of SONET, operating at 51.84 Mbps. Faster SONET rates are

defined as STS- n , where n is a multiple of 51.84 Mbps. See also SONET .

stub area

In OSPF, an area through which, or into which, AS external advertisements are not

flooded.

subnet mask

Number of bits of the network address used for the host portion of a Class A, Class

B, or Class C IP address.

subrate value

Value that reduces the maximum allowable peak rate by limiting the

HDLC-encapsulated payload. The subrate value must exactly match that of the

remote channel service unit (CSU).

summary link

OSPF link-statement advertisement flooded throughout the advertisement’s

advertisement

associated areas by area border routers to describe the routes that they know about

in other areas.

SVC

Switched virtual connection. A dynamically established, software-defined logical

connection that stays up as long as data is being transmitted. Once transmission is

complete, the software tears down the SVC. See also PVC.

switch-card chassis

See SCC .

switched virtual

See SVC .

connection

Synchronous Static

See SSRAM .

Random Access

Memory

system ID

System identifier. Portion of the ISO nonclient peer. The system ID can be any six

bytes that are unique throughout a domain.

38 „ S

: Glossary

System and Switch

See SSB .

Board

T

T1

Basic physical layer protocol used by the Digital Signal level 1 (DS1) multiplexing

method in North America. A T1 interface operates at a bit rate of 1.544 Mbps and

can support 24 DS0 channels.

T3

Physical layer protocol used by the Digital Signal level 3 (DS3) multiplexing method

in North America. A T3 interface operates at a bit rate of 44.736 Mbps.

TACACS+

Terminal Access Controller Access Control System Plus. Authentication method for

validating users who attempt to access the router using telnet.

tail drop

Queue management algorithm for dropping packets from the input end (tail) of the

queue when the length of the queue exceeds a configured threshold. See also RED .

TCP

Transmission Control Protocol. Works in conjunction with the Internet Protocol (IP)

to send data over the Internet. Divides a message into packets and tracks the

packets from point of origin to destination.

TDMA

Time-Division Multiplex Access. A type of multiplexing in which two or more

channels of information are transmitted over the same link, where the channels

take turns to use the link. Each link is allocated a different time interval ("slot" or

"slice") for the transmission of each channel. For the receiver to distinguish one

channel from the other, some kind of periodic synchronizing signal or

distinguishing identifier is required. See also GSM.

Third-generation

See 3GPP .

Partnership Project

Time-Division Multiplex

See TDMA.

Access

TNP

Trivial Network Protocol. A Juniper Networks proprietary protocol automatically

configured on an internal interface by the JUNOS software. It is used to

communicate between the Routing Engine and components of the Packet

Forwarding Engine and is critical to the operation of the router.

ToS

Type of service. The method of handling traffic using information extracted from

the fields in the ToS byte to differentiate packet flows.

traffic engineering

Process of selecting the paths chosen by data traffic in order to balance the traffic

load on the various links, routers, and switches in the network. (Definition from

http://www.ietf.org/internet-drafts/draft-ietf-mpls-framework-04.txt.) See also MPLS.

traffic engineering class

In Differentiated-Services-aware traffic engineering, a paired class type and priority.

traffic engineering class

In Differentiated-Services-aware traffic engineering, a map among the class types,

map

priorities, and traffic engineering classes. The traffic engineering class mapping

must be consistent across the Differentiated Services domain.

T „ 39

JUNOS 7.2 Comprehensive Index and Glossary

traffic shaping

For class of service, a traffic regulation mechanism that controls the traffic going out

of an interface in order to match its flow to the speed of the remote, target interface

and to ensure that the traffic conforms to policies contracted for it. Traffic adhering

to a particular profile can be shaped to meet downstream requirements, thereby

eliminating bottlenecks in topologies with data-rate mismatches. A shaper typically

delays excess traffic using a buffer, or queuing mechanism, to hold packets and

shape the flow when the data rate of the source is higher than expected. See also

shaping rate .

transit area

In OSPF, an area used to pass traffic from one adjacent area to the backbone, or to

another area if the backbone is more than two hops away from an area.

transit router

In MPLS, any intermediate router in the LSP between the ingress router and the

egress router.

transport mode

IPSec mode of operation in which the data payload is encrypted, but the original IP

header is left untouched. The IP addresses of the source or destination can be

modified if the packet is intercepted. Because of its construction, transport mode

can be used only when the communication endpoint and cryptographic endpoint

are the same. VPN gateways that provide encryption and decryption services for

protected hosts cannot use transport mode for protected VPN communications. See

also tunnel mode .

trap

Reports significant events occurring on a network device, most often errors or

failures. SNMP traps are defined in either standard or enterprise-specific MIBs.

Triple Data Encryption

See 3DES.

Standard

Trivial Network Protocol

See TNP .

trunk mode

A Layer 2 circuit cell-relay transport mode that allows you to send ATM cells

between ATM2 IQ interfaces over an MPLS core network. You use Layer 2 circuit

trunk mode (as opposed to standard Layer 2 circuit cell-relay mode) to transport

ATM cells over an MPLS core network that is implemented between other vendors'

switches or routers. The multiple connections associated with a trunk increase

bandwidth and provide failover redundancy. See also AAL5 mode , cell-relay mode ,

Layer 2 circuits , and standard AAL5 mode .

tunnel

Private, secure path through an otherwise public network.

tunnel mode

IPSec mode of operation in which the entire IP packet, including the header, is

encrypted and authenticated and a new VPN header is added, protecting the entire

original packet. This mode can be used by both VPN clients and VPN gateways, and

protects communications that come from or go to non-IPSec systems. See also

transport mode .

Tunnel PIC

Physical interface card that allows the router to perform the encapsulation and

decapsulation of IP datagrams. The Tunnel PIC supports IP-IP, GRE, and PIM register

encapsulation and decapsulation. When the Tunnel PIC is installed, the router can

be a PIM rendezvous point (RP) or a PIM first-hop router for a source that is directly

connected to the router.

type of service

See ToS .

40 „ T

: Glossary

TX Matrix platform

Routing platform that provides the centralized switching fabric of the routing

matrix.

U

UDP

User Datagram Protocol. In TCP/IP, a connectionless transport layer protocol that

exchanges datagrams without acknowledgments or guaranteed delivery, requiring

that error processing and retransmission be handled by other protocols.

UME

UNI management entity. The code residing in the ATM devices at each end of a UNI

(user-to-network interface) circuit that functions as an SNMP agent, maintaining

network and connection information specified in an ILMI MIB.

UMTS

Universal mobile telecommunications system. Third-generation (3G), packet-based

transmission of text, digitized voice, video, and multimedia, at data rates up to 2

Mbps.

UNI

User-to-network interface. ATM Forum specification that defines an interoperability

standard for the interface between a router or an ATM switch located in a private

network and the ATM switches located within the public carrier networks. Also used

to describe similar connections in Frame Relay networks.

UNI management entity

See UME .

unicast

Operation of sending network traffic from one network node to another individual

network node.

UPS

Uninterruptible power supply. A device that sits between a power supply and a

router (or other piece of equipment) and prevents undesired power-source events,

such as outages and surges, from affecting or damaging the device.

User Datagram Protocol

See UDP .

UTRAN

UMTS Terrestrial Radio Access Network. The WCDMA radio network in UMTS.

V

vapor corrosion inhibitor

See VCI.

variable bit rate

See VBR .

VBR

Variable bit rate. For ATM1 and ATM2 intelligent queuing (IQ) interfaces, data that is

serviced at a varied rate within defined limits. VBR traffic adds the ability to

statistically oversubscribe user traffic.

VC

Virtual circuit. A software-defined logical connection between two network devices

that is not a dedicated connection but acts as though it is. It can be either

permanent (PVC) or switched (SVC). VCs are used in ATM, Frame Relay, and X.25.

See also VPI, VCI, PVC, and SVC.

VCI

1. Vapor corrosion inhibitor. Small cylinder packed with the router that prevents

corrosion of the chassis and components during shipment.

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JUNOS 7.2 Comprehensive Index and Glossary

2. Virtual circuit identifier. A 16-bit field in the header of an ATM cell that indicates

the particular virtual circuit the cell takes through a virtual path. Also called a

logical interface . See also VPI .

virtual channel

Enables queuing, packet scheduling, and accounting rules to be applied to one or

more logical interfaces. See also virtual channel group .

virtual channel group

Combines virtual channels into a group and then applies the group to one or more

logical interfaces. See also virtual channel .

virtual circuit identifier

See VCI.

virtual connection

See VC.

virtual LAN

A tagged frame whose tag header carries both VLAN identification and priority

(VLAN)-tagged frame

information.

virtual link

In OSPF, a link created between two routers that are part of the backbone but are

not physically contiguous.

virtual local area

See VLAN .

network

virtual path identifier

See VPI .

virtual private network

See VPN .

Virtual Router

See VRRP .

Redundancy Protocol

VLAN

Virtual local area network. A logical group of network devices that appear to be on

the same LAN, regardless of their physical location. VLANs are configured with

management software, and are extremely flexible because they are based on

logical, rather than physical, connections.

VPI

Virtual path identifier. An 8-bit field in the header of an ATM cell that indicates the

virtual path the cell takes. See also VCI.

VPN

Virtual private network. A private data network that makes use of a public TCP/IP

network, typically the Internet, while maintaining privacy with a tunneling protocol,

encryption, and security procedures.

VRF instance

VPN routing and forwarding instance. A VRF instance for a Layer 3 VPN

implementation that consists of one or more routing tables, a derived forwarding

table, a set of interfaces that use the forwarding table, and a set of policies and

routing protocols that determine what goes into the forwarding table.

VRRP

Virtual Router Redundancy Protocol. On Fast Ethernet and Gigabit Ethernet

interfaces, allows you to configure virtual default routers.

42 „ V

: Glossary

W

WAP

Wireless Application Protocol. A standard protocol that enables mobile users to

access the Internet in a limited fashion if WAP is supported and enabled on the

mobile device, the server, and the wireless network. WAP users can send and

receive e-mails and access Web sites in text format only (WAP does not support

graphics).

wavelength-division

See WDM .

multiplexing

WCDMA

Wideband Code Division Multiple Access. Radio interface technology used in most

third-generation (3G) systems.

WDM

Wavelength-division multiplexing. Technique for transmitting a mix of voice, data,

and video over various wavelengths (colors) of light.

weighted round-robin

See WRR .

Windows Internet Name

See WINS.

Service

WINS

Windows Internet Name Service. A Windows name resolution service for network

basic input/output system (NetBIOS) names. WINS is used by hosts running

NetBIOS over TCP/IP (NetBT) to register NetBIOS names and resolve NetBIOS

names to Internet Protocol (IP) addresses.

WRR

Weighted round-robin. Scheme used to decide the queue from which the next

packet should be transmitted.

X

XENPAK

A standard that defines a type of pluggable fiber-optic transceiver module which is

compatible with the 10 Gigabit Ethernet (10 GbE) standard.

XENPAK-ZR -

A media type used for long-reach, single-mode (80-120 km) 10-Gigabit Ethernet

10GBASE-ZR XENPAK

metro applications.

XENPAK-SR 10BASE-SR

A media type that supports a link length of 26 meters on standard Fiber Distributed

XENPAK

Data Interface (FDDI) grade multimode fiber (MMF). Up to 300-meter link lengths

are possible when using 2000 MHz/km MMF (OM3).

XML

Extensible Markup Language. Language used for defining a set of markers, called

tags, that define the function and hierarchical relationships of the parts of a

document or data set.

XML schema

Definition of the elements and structure of one or more Extensible Markup

Language (XML) documents. Similar to a document type definition (DTD), but with

additional information and is written in XML.

XOR

Exclusive or. A logical operator (exclusive disjunction) in which the operation yields

the result of true when one, and only one, of its operands is true.

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JUNOS 7.2 Comprehensive Index and Glossary

Z

zeroize

A term used to describe the process of removing all sensitive information such as

cryptographic keys and user passwords, from a router running JUNOS-FIPS.

44 „ Z