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.

database description packet

OSPF packet type used in the formation of an adjacency. The packet sends summary information about the local router's database to the neighboring router.

data circuit-terminating equipment

See DCE.

data-driven multicast distribution tree tunnel

See data-MDT.

Data Encryption Standard

See DES.

data-link connection identifier

See DLCI.

data link switching

See DLSw.

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 plane

Virtual network path used to distribute data between nodes. See also control plane.

data service unit

See CSU/DSU.

data terminal equipment

See DTE.

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.

D-channel

Delta channel. A circuit-switched channel that carries signaling and control for B channels. In Basic Rate Interface (BRI) applications, it can also support customer packet data traffic at speeds up to 9.6 kbps. See also B-channel and BRI.

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.

deactivate

Method of modifying the router's active configuration. Portions of the hierarchy marked as inactive using this command are ignored during the router's commit process as if they were not configured at all.

dead interval

Amount of time that an OSPF router maintains a neighbor relationship before declaring that neighbor as no longer operational. The JUNOS software uses a default value of 40 seconds for this timer.

dead-peer detection

See DPD.

default address

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

default route

Route used to forward IP packets when a more specific route is not present in the routing table. Often represented as 0.0.0.0/0, the default route is sometimes referred to as the route of last resort.

delta channel

See D-channel.

demand circuit

Interface configured for dial-on-demand routing. In OSPF, the demand circuit reduces the amount of OSPF traffic by removing all OSPF protocols when the routing domain is in a steady state.

denial of service

See DoS.

dense mode

Method of forwarding multicast traffic to interested listeners. Dense mode forwarding assumes that most of the hosts on the network will receive the multicast data. Routers flood packets and prune unwanted traffic every 3 minutes.

dense wavelength-division multiplexing

See DWDM.

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 (LSAs) 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 length

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

destination service access point

See DSAP.

device control process

See dcd.

DFC

Dynamic flow capture. Process of collecting packet flows that match a particular filter list to one or more content destinations using an on-demand control protocol that relays requests from one or more control sources.

DHCP

Dynamic Host Configuration Protocol. Allocates IP addresses dynamically so that they can be reused when no longer needed.

dialer interface

Logical interface for configuring dialing properties and the control interface for a backup ISDN connection.

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 aware

See DiffServ-aware.

Differentiated-
Services-
aware traffic engineering

Type of constraint-based routing that can enforce different bandwidth constraints for different classes of traffic. It can also do call admission control (CAC) on each traffic engineering class when a label-switched path (LSP) is established.

Differentiated Services code point

See DSCP.

Differentiated Services domain

Routers in a network that have Differentiated Services enabled.

Diffie-Hellman

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.

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.

disable

Method of modifying the router's active configuration. Portions of the hierarchy marked as disabled (mainly router interfaces) cause the router to use the configuration but stop the pertinent operation of the configuration.

discard

JUNOS software syntax command used in a routing policy or a firewall filter. The command halts the logical processing of the policy or filter when a set of match conditions is met. The specific route or IP packet is dropped from the network silently. It can also be a next-hop attribute assigned to a route in the routing table.

discard-eligible bit

See DE.

distance-vector

Method used in Bellman-Ford routing protocols to determine the best path to all routers in the network. Each router determines the distance (metric) to the destination and the vector (next hop) to follow.

Distributed Buffer Manager ASICs

Juniper Networks ASIC responsible for managing the router's packet storage memory.

DLCI

Data-link connection identifier. Identifier for a Frame Relay virtual connection (also called a logical interface).

DLSw

Data link switching. Method of tunneling IBM System Network Architecture (SNA) and NetBIOS traffic over an Internet Protocol (IP) network. (The JUNOS software does not support NetBIOS.) See also tunneling protocol.

DLSw circuit

Path formed by establishing data link control (DLC) connections between an end system and a local router configured for DLSw. Each DLSw circuit is identified by the circuit ID that includes the end system method authenticity check (MAC) address, local service access point (LSAP), and DLC port ID. Multiple DLSw circuits can operate over the same DLSw connection.

DLSw connection

Set of TCP connections between two DLSw peers that is established after the initial handshake and successful capabilities exchange.

DNS

Domain Name System. A system that stores information about hostnames and domain names. DNS provides an IP address for each hostname, and lists the e-mail exchange servers accepting e-mail addresses for each domain.

document type definition

See DTD.

Domain Name System

See DNS.

DoS

Denial of service. A 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 random early detection (RED) to determine from which queue to drop packets.

DSAP

Destination service access point. Service access point (SAP) that identifies the destination for which a logical link control protocol data unit (LPDU) is intended.

DS0

Digital signal level 0. In T-carrier systems, a basic digital signaling rate of 64 Kbps. The DS0 rate forms the basis for the North American digital multiplex transmission hierarchy.

DS1

Digital signal level 1. In T-carrier systems, a digital signaling rate of 1.536 Mbps. A standard used in telecommunications to transmit voice and data between devices. Also known as T1. See T1.

DS3

Digital signal level 3. In T-carrier systems, a digital signaling rate of 44.736 Mbps. This level of carrier can transport 28 DS1 level signals and 672 DS0 level channels within its payload. Also known as T3. See T3.

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. DSU 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.

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 Configuration Protocol

See DHCP.

dynamic label-switched path

MPLS network path established by signaling protocols such as RSVP and LDP.