Transcript Chapter 15 PowerPoint

Chapter Overview


Modems
The Internet and Web Browsers
1
Modem Basics



A modem allows computers to communicate over
telephone lines by modulating and demodulating
signals.
Integrated Services Digital Network (ISDN) uses a
terminal adapter (TA) for high-speed digital
connections.
You should understand the following terms:



Baud rate
Bits per second (bps)
IP address

Transmission Control
Protocol/Internet Protocol
(TCP/IP)
2
Communication
3
Digital Communication


Asynchronous communication does not use a
common data clock.
Synchronous communication uses the system
clock at timed intervals.
4
How Communication Protocols Work
5
Hardware



Internal modems
Universal serial bus (USB) modems
External analog modems
6
ISDN Terminal Adapters



ISDN is an all-digital phone connection that
carries voice and high-speed data
transmissions.
ISDN uses a TA instead of a modem.
TAs are difficult to install.
7
The RS-232 Port


The Electronic Industries Association (EIA)
developed the RS-232 standard for low-speed
data communication.
The RS-232 cable uses either a 25-pin or
9-pin connector.
8
Telephone-Line Basics for Modems



Half-duplex uses RJ-11 and has two wires, so
it can send or receive only one signal at a
time.
Full-duplex uses RJ-12 and has four wires, so
it can simultaneously send and receive.
Multifunction modems can send faxes and
handle voice mail.
9
Modem Installation


Installing an internal modem expansion card
requires you to check settings, install the
board and drivers, and set up the command
set.
Installing an external modem requires you to
connect to a COM port, plug in the cabling,
and configure the software.
10
Modem Speeds




Modem speed is measured in baud rate and
bps.
Baud rate is the number of voltage or
frequency changes per second.
Bps is the actual number of bits that are
transmitted per baud cycle.
CCITT (Comité Consultatif International
Télégraphique et Téléphonique) sets modem
speed standards.
11
Fax Speeds



Groups 1 and 2 pertain to slower analog
devices.
Group 3 is for digital equipment.
Group 4 allows the highest resolution of
output.
12
Information Transfer Protocols





American Standard Code for Information
Interchange (ASCII) is an old protocol that
uses the standard ASCII character set.
Kermit was an early synchronous protocol
that is rarely used today.
Xmodem transfers data in 128-byte blocks
and uses parity error checking.
Ymodem transfers data in 1024-byte blocks.
Zmodem adds new features: crash recovery,
automatic downloading, and streaming file
transfer.
13
Handshaking




Handshaking negotiates the communication
rules between modems.
Modems on both ends must agree on the
rules.
Modems can handle flow control through
hardware or software.
Hardware flow control is faster and more
dependable.
14
Modem Standards





Modem standards include error detection and
data compression standards.
Manufacturers and standards committees
develop communication standards.
Bell Telephone developed early modem
standards 103 and 212A.
CCITT modem standards are commonly
known as Vdot standards.
The V.90 standard has replaced K56flex and
x2 as the 56-Kbps modem standard.
15
Modem Commands



The Hayes AT command set is an unofficial
standard.
Commands can be used for troubleshooting.
The computer must be in terminal mode to
use these commands.
16
Troubleshooting
17
Troubleshooting (Cont.)
18
The Internet




The Internet is a worldwide network that
uses TCP/IP.
The World Wide Web (WWW) is a subset of
the Internet.
Web sites are hosted by computers that
house the content.
A browser is client software designed to
access the WWW.
19
Electronic Mail

E-mail requires the following:





E-mail server
User account on that server
Client program to send and receive e-mail
Account information
You can configure a client program to
automatically download e-mail.
20
Internet Protocols and Services






File Transfer Protocol (FTP) is used to transfer files.
TCP/IP is the standard suite of protocols used on the
Internet.
Each host on an IP network requires a unique 32-bit
binary address.
Internet Service Providers (ISPs) provide the
connection between dial-up users and the Internet.
Domain Name System (DNS) identifies domain names
on the Internet.
A DNS server matches DNS names to IP addresses.
21
Getting Connected




Different types of connections require
different hardware and support.
A firewall between a computer and the
Internet provides security.
ISPs provide services and connections.
A browser allows you to access and view Web
pages.
22
Using the PING Command
23
Chapter Summary







Modems convert parallel digital data to and from
serial analog data.
Modems can be installed internally or externally.
Modem speeds are measured in bps.
AT commands are used to manually communicate
with and test a modem.
The Internet provides information and services that
are made available through browsers.
The Internet uses DNS and TCP/IP to route traffic.
The PING command can be used to troubleshoot IP
networks.
24