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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.

callback — Alternative feature to dial-in that enables a J-series Services Router to call back the caller from the remote end of a backup ISDN connection. Instead of accepting a call from the remote end of the connection, the router rejects the call, waits a configured period of time, and calls a number configured on the router’s dialer interface. See also dial-in.

Call Detail Record — See CDR.

caller ID — Telephone number of the caller on the remote end of a backup ISDN connection, used to dial in and also to identify the caller. Multiple caller IDs can be configured on an ISDN dialer interface. During dial-in, the router matches the incoming call’s caller ID against the caller IDs configured on its dialer interfaces. Each dialer interface accepts calls only from callers whose caller IDs are configured on it.

CAMEL — Customized Applications of Mobile Enhanced Logic. An ETSI standard for GSM networks that enhances the provision of Intelligent Network services.

candidate configuration — File maintained by the JUNOS software containing changes to the router’s active configuration. This file becomes the active configuration when a user issues the commit command.

candidate RP advertisements — Information sent by routers in a multicast network when they are configured as a local rendezvous point. This information is unicast to the bootstrap router for the multicast domain.

carrier-of-carriers VPN — 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 in which 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 need to periodically burst to a higher rate, such as nonpacketized voice and audio.

CCC — Circuit cross-connect. A JUNOS software feature that allows you to configure transparent connections between two circuits. A circuit can be a Frame Relay DLCI, an ATM virtual channel (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 — Customer edge. The customer router that is connected to the service provider network.

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 — 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 — Layer 2 circuit transport mode that sends 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, trunk mode.

cell tax — Physical transmission capacity used by header information when sending data packets in an ATM network. Each ATM cell uses a 5-byte header.

central office — See CO.

certificate authority — See CA.

certificate revocation list — See CRL.

CFEB — Compact Forwarding Engine Board. In M7i and M10i routers, provides route lookup, filtering, and switching to the destination port.

cflowd — Application available from CAIDA that collects an aggregate of sampled flows and sends the aggregate to a specified host running the cflowd application.

CFM — Connectivity fault management. An end-to-end per-service-instance Ethernet layer operation, administration, and management (OAM) protocol. CFM includes proactive connectivity monitoring, fault verification, and fault isolation for large Ethernet metropolitan-area networks.

Challenge Handshake Authentication Protocol — See CHAP.

channel — Communication circuit linking two or more devices. A channel provides an input/output interface between a processor and a peripheral device, or between two systems. A single physical circuit can consist of one or many channels, or two systems carried on a physical wire or wireless medium. For example, the dedicated channel between a telephone and the central office (CO) is a twisted-pair copper wire. See also frequency-division multiplexed channel, time-division multiplexed channel.

channel group — Combination of DS0 interfaces partitioned from a channelized interface into a single logical bundle.

channelized E1 — A 2.048-Mbps interface that can be configured as a single clear-channel E1 interface or channelized into as many as 31 discrete DS0 interfaces. On most channelized E1 interfaces, time slots are numbered from 1through 32, and time slot 1 is reserved for framing. On some legacy channelized E1 interfaces, time slots are numbered from 0 through 31, and time slot 0 is reserved for framing.

channelized interface — Interface that is a subdivision of a larger interface, minimizing the number of Physical Interface Cards (PICs) or Physical Interface Modules (PIMs) that an installation requires. On a channelized PIC or PIM, each port can be configured as a single clear channel or partitioned into multiple discrete T3, T1, E1, and DS0 interfaces, depending on the size of the channelized PIC or PIM.

channelized T1 — A 1.544-Mbps interface that can be configured as a single clear-channel T1 interface or channelized into as many as 24 discrete DS0 interfaces. Time slots are numbered from 1 through 24.

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.

chassisd — Chassis daemon. A JUNOS software process responsible for managing the interaction of the router’s physical components.

chassis daemon — See chassisd.

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.

CIR — Committed information rate. The CIR specifies the average rate at which packets are admitted to the network. As each packet enters the network, it is counted. Packets that do not exceed the CIR are marked green, which corresponds to low loss priority. Packets that exceed the CIR but are below the peak information rate (PIR) are marked yellow, which corresponds to medium loss priority. See also trTCM, PIR.

circuit cross-connect — See CCC.

Cisco-RP-Announce — Message advertised into a multicast network by a router configured as a local rendezvous point (RP) in an auto-RP network. A Cisco-RP-Announce message is advertised in dense-mode PIM to the 224.0.1.39 multicast group address.

Cisco-RP-Discovery — Message advertised by the mapping agent in an auto-RP network. A Cisco-RP-Discovery message contains the rendezvous point (RP) to multicast group address assignments for the domain. It is advertised in dense-mode PM to the 224.0.1.40 multicast group address.

CIST — Common and internal spanning tree. The single spanning tree calculated by the Spanning Tree Protocol (STP) and the Rapid Spanning Tree Protocol (RSTP) and the logical continuation of that connectivity through multiple spanning-tree (MST) bridges and regions, calculated to ensure that all LANs in the bridged LAN are simply and fully connected. See also MSTI.

classification — In class of service (CoS), the examination of an incoming packet that associates the packet with a particular CoS servicing level. There are two kinds of classifiers, behavior aggregate and multifield. See also BA classifier, multifield classifier.

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 routing — See CIDR.

class of service — See CoS.

class-of-service process — See cosd.

Class Selector code point — See CSCP.

class type — In Differentiated-Services-aware traffic engineering, a collection of traffic flows that are 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.

clear channel — Interface configured on a channelized PIC or PIM that operates as a single channel, does not carry signaling, and uses the entire port bandwidth.

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.

CLNS — Connectionless Network Service. A Layer 3 protocol, similar to Internet Protocol version 4 (IPv4). CLNS uses network service access points (NSAP) instead of the prefix addresses found in IPv4 to specify end systems and intermediate systems.

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.

CO — Central office. The local telephone company building that houses circuit switching equipment used for subscriber lines in a given area.

Code Division Multiple Access — See CDMA.

code-point alias — Name assigned to a pattern of code-point bits. This name is used, instead of the bit pattern, in the configuration of other class-of-service (CoS) components, such as classifiers, drop-profile maps, and rewrite rules.

command completion — Function of a router’s command-line interface (CLI) that allows a user to enter only the first few characters in any command. Users access this function through the Spacebar or Tab key.

command-line interface — See CLI.

commit — JUNOS software command-line interface (CLI) configuration-mode command that saves changes made to a router configuration, verifies the syntax, applies the changes to the configuration currently running on the router, and identifies the resulting file as the current operational configuration.

commit script — Script that enforces custom configuration rules. A script runs each time a new candidate configuration is committed and inspects the configuration. If a configuration breaks your custom rules, the script can generate actions for the JUNOS software.

commit script macro — Sequence of commands that allow you to create custom configuration syntax to simplify the task of configuring a routing platform. By itself, your custom syntax has no operational impact on the routing platform. A corresponding commit script macro uses your custom syntax as input data for generating standard JUNOS configuration statements that execute your intended operation.

committed information rate — See CIR.

common and internal spanning tree — See CIST.

Common Criteria — International standard (ISO/IEC 15408) for computer security. See also EAL3

Common Criteria Evaluation Assurance Level 3 — See EAL3.

Common Language Equipment Identifier — See CLEI.

community — 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.

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 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.

Compact Forwarding Engine Board — See CFEB.

competitive local exchange carrier — See CLEC.

complete sequence number PDU — See CSNP.

Compressed Real-Time Transport Protocol — See CRTP.

Concurrent Versions System — See CVS.

confederation — In BGP, a group of systems that appears to external autonomous systems as a single autonomous system.

configuration mode — JUNOS software mode that allows a user to alter the router’s current configuration.

Connect — BGP neighbor state in which the local router has initiated the TCP session and is waiting for the remote peer to complete the TCP connection.

Connectionless Network Protocol — See CLNP.

Connectionless Network Service — See CLNS.

Connectivity fault management — See CFM.

Connector Interface Panel — See CIP.

constant bit rate — See CBR.

constrained path — In traffic engineering, a path determined using the CSPF algorithm. The ERO carried in the RSVP packets contains the constrained path information. See also ERO.

Constrained Shortest Path First — See CSPF.

context node — Node that the Extensible Stylesheet Language for Transformations (XSLT) processor is currently examining. XSLT changes the context as it traverses the XML document’s hierarchy. see also XSLT.

context-sensitive help — Function of the router’s command-line interface (CLI) that allows a user to request information on the JUNOS software hierarchy. You can access context-sensitive help in both operational and configuration mode.

contributing routes — Active IP routes in the routing table that share the same most-significant bits and are more specific than an aggregate or generate route.

Control Board — See CB.

control plane — Virtual network path used to set up, maintain, and terminate data plane connections. See also data plane.

Cooperative Association for Internet Data Analysis — See CAIDA.

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.

cosd — Class-of-service process that enables the routing platform to provide different levels of service to applications based on packet classifications.

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 Parameter — See CSP.

CRL — Certificate revocation list. A list of digital certificates that have been invalidated, including the reasons for revocation and the names of the entities that issued them. A CRL prevents usage of digital certificates and signatures that have been compromised.

CRTP — Compressed Real-Time Transport Protocol. Protocol that decreases the size of the IP, UDP, and RTP headers and works with reliable and fast point-to-point links for voice over IP (VoIP) traffic. CRTP is defined in RFC 2508.

Crypto Accelerator Module — Processor card that speeds up certain cryptographic IP Security (IPSec) services on some J-series Services Routers. For the supported cryptographic algorithms, See the J-series documentation.

Crypto Officer — Superuser responsible for the proper operation of a router running JUNOS-FIPS software.

CSCP — Class Selector code point. Eight Differentiated Services code point (DSCP) values of the form xxx000 (where x can 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. On routers running JUNOS-FIPS software, a collection of cryptographic keys and passwords that must be protected at all times.

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 — See CE.

customer edge device — See CE device.

customer premises equipment — See CPE.

Customized Applications of Mobile Enhanced Logic — See CAMEL.

CVS — Concurrent Versions System. A widely used version control system for software development or data archives.

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