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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.
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