Chapter 7Ben Bielskis

WAN

Wide Area Network Connects LANs over a large

geographical area. WAN Link – A connection from one

site to another.

PSTN

Public Switched Telephone Network

Also known as POTS. (Plain Old Telephone Service)

PSTN is adequate for most dial-up connections to LANs.

Doesn’t have the ability to ensure quality or throughput required by many WAN applications.

Modem

Modulator/Demodulator Converts digital pulses into analog

signals for the PSTN.

POP

Point of Presence The place where two telephone

systems meet.

ISDN

Integrated Services Digital Network International standard for

transmitting data over digital lines.

TE

Terminal equipment ISDN devices that may include

cards or simply standalone devices to connect computers to an ISDN line.

TA

Terminal Adapter Converts digital signals into analog

signals for use with ISDN phones and other analog devices.

DSL

Digital Subscriber Lines Uses data modulation techniques

to achieve extraordinary throughput over regular phone lines.

Data modulation is when one signal alters the frequency.

Upstream/Downstream

Upstream refers to data traveling from the customer to the carrier’s POP.

Downstream refers to data traveling from the carrier’s POP to the customer.

Symmetrical/Asymmetrical

Asymmetrical is a technology that offers more throughput in one direction than in the other.

Symmetrical provides equal capacity for data traveling both upstream and downstream.

T-carriers

A collection of T1, fractional T1, and T3 lines.

As a networking professional you will most likely work with T1 and T3 lines.

CSU/DSU

Channel Service Unit/Data Service Unit

The connection point for a T1 line at the customer’s site.

Multiplexer

A device that combines multiple voice or data channels on one line.

Devices that connect to the multiplexer are known as terminal equipment.

Routers and Bridges

On T1 networks they consist of Routers, Bridges, or the combination of the two.

FDDI

Fiber Distributed Data Interface The networking standard originally

specified by ANSI in the mid 1980’s and later refined by ISO.

Uses dual fiber-optic ring to transmit data at speeds of 100 Mbps.

CIR

Committed information rate A minimum amount of bandwidth

guaranteed by the service provider.

ATM

Asynchronous Transfer Mode A WAN transmission method that

relies on a fixed packet size to achieve data transfer rates from 25 to 622 Mbps.

Applications that benefit from ATM technology are those that are time sensetive.

SONET

Synchronous Optical Network Provides data transfer rates from

64 Kbps to 2.4 Gbps using the same TDM technique used by T-carriers.

VPN

Virtual Private Network Long-distance networks logically

defined over public transmission systems that serve all of an organization’s users, but isolate that organization’s traffic from other users of the same public lines.

Dial-up networking

Refers to the process of dialing into a LAN’s access server or to an ISP.