Part of a network that acts as the primary path, usually high-speed, for traffic that is most often sourced from, and destined for, other networks.
Backhaul Router
Another term used to describe a default gateway router. The Cisco AS5300 network access server can be used as a default gateway router. See Default Gateway.
BRI
Basic Rate Interface. The BRI 0 interface corresponds to dsl 0, which has three channels—two bearer channels and one data channel (2B + D).
B Channel
Bearer Channel. A 64 Kbps channel used in ISDN that provides full-duplex communication for the user.
C
CCB
Call Control Block. The CCB counter increases by 1 for each active call on the Cisco 1604. The CCB counter for one call is destroyed upon disconnect.
CHAP
Challenge Handshake Authentication Protocol. Security feature supported on lines using PPP encapsulation that prevents unauthorized access. CHAP does not itself prevent unauthorized access, but merely identifies the remote end. The router or access server then determines whether that user is allowed access.
Client
Equipment. Refers to PC and the modem. Node or software program (front-end device) that requests services from a server.
D
D Channel
Data Channel. A 16 Kbps (BRI) or 64 Kbps (PRI) full-duplex ISDN channel.
Default Gateway
The router that all packets are sent to when the sending device does not have the address of the destination device. The default gateway then forwards the incoming packets to other appropriate networks and becomes the static route to the other networks. Cisco AS5300 network access servers can be configured to be default gateways. See also Backhaul Router.
DSL
Digital Subscriber Line. A public network technology that delivers high bandwidth over conventional copper wiring at limited distances. Because most DSL technologies do not use the whole bandwidth of the twisted pair, there is room left for a voice channel.
E
Easy IP
An implementation of port address translation (PAT), which vastly simplifies IP addressing design when supporting remote sites.
G
Gateway
In the IP community, an older term referring to a routing device. Today, the term router is used to describe nodes that perform this function, and gateway refers to a special-purpose device that performs an application layer conversion of information from one protocol stack to another.
H
Hunt group number
The PRI telephone number assigned to the central site that distributes calls among the available B channels.
I
IP Backbone
The part of a network that acts as the primary path for traffic that is most often sourced from, and destined for, other networks.
ISDN
Integrated Services Digital Network.
L
LAN
The router and the subnet behind it. The remote LAN is the ISDN router and the IP subnet behind it.
LCP
Link Control Protocol.
LDN
Local Directory Number.
N
Node
Can be a client (PC, Mac, UNIX). Connected to an analog modem.
P
PAP
Password Authentication Protocol. Authentication protocol that allows PPP peers to authenticate one another. The remote router attempting to connect to the local router is required to send an authentication request. Unlike CHAP, PAP passes the password and host name or username in the clear (unencrypted). PAP does not itself prevent unauthorized access, but merely identifies the remote end. The router or access server then determines if that user is allowed access. PAP is supported only on PPP lines.
PAT
Port address translation.
PRI
Primary Rate Interface. ISDN interface to Primary Rate Access. Primary Rate Access consists of a single 64 Kbps D (data) channel plus 23 (T1) or 30 (E1) B (bearer) channels for voice or data.
S
SPID
Service Profile Identifier. Number that some service providers use to define the services to which an ISDN device subscribes. The ISDN device uses the SPID when accessing the switch that initializes the connection to a service provider.
Spoofing
A term in the CLI that means that the interface is presenting itself to the Cisco IOS software as being up and operational.
T
TEI
Terminal Equipment Identifier.
TTY
Basic asynchronous ASCII-coded data communications.
