Chapter 8 Communications and Networks
Communications
set-top boxes
mainframecomputers
smartphones
notebookcomputers servers
Web-enabledPDAs
desktopcomputers
Tablet PCs
GPS receivers
Process in which two or more computers or devices transfer data, instructions, and information
Sending device — initiates
instruction to transmit data, instructions, or
information
Successful Communications—5 components
Communications device — connects the communications
channel to the receiving device
Receiving device — accepts
transmission of data, instructions, or
information
Communications device — connects
the sending device to the communications
channel
Communications channel — media
on which data, instructions, or
information travel
Types of Networks Collection of computers and devices connected via communications devices and transmission
media
Local Area Network (LAN) Network in limited geographical area—office building
Metropolitan area network (MAN)—covers city Wide area network (WAN)
Potentially world-wide coverage Internet is the largest WAN
Types of Networks
Client/Server Peer to PeerSimple network that connects fewer than 10 computersEach computer has equal capabilities
One or more computers act as server and other computers, or clients, access server
Types of Networks
What is Internet peer-to-peer (P2P)? Intranet
Restricted network usually within an organizationAllows sharing of organizational-related info without putting it out for public reading
Nextp. 292 Fig. 8-11
Enables users to connect to each other’s hard disks and exchange files directly
Networks Topology
Layout of devices in a networkBus network
All computers and devices connect to a central cable, or bus
Ring networkCable forms closed ring, or loop, with all computers and devices arranged along ring
Networks Topology
Star network
Nextp. 293 Fig. 8-14
All devices connect to a central device, called hub
All data transferred from one computer to another passes through hub
Ethernet and Token Ring Technology
Ethernet technology allows computers to contend for access to network
If two computers send data at same time, a collision occurs and computers must send again
Token ring technology controls access to network by requiring devices to pass a special signal, called token
Networks
TCP/IP and 802.11 BlueToothShort-range radio waves transmitdata between Bluetooth devices
Nextp. 294
TCP/IP (Transmission Control Protocol/Internet Protocol) technology transmits data by breaking it up into small pieces, or packets Commonly used for
Internet transmissions 802.11 is family of
standards for wireless LANs
Networks
What are IrDA, RFID, and Wireless Applications Protocol (WAP)?
p. 294
IrDAIrDAspecification allows data to be transferred wirelessly via infrared light waves
IrDAIrDAspecification allows data to be transferred wirelessly via infrared light waves
Wireless Applications Wireless Applications Protocol (WAP)Protocol (WAP) allow wireless mobile devices to access Internet
Wireless Applications Wireless Applications Protocol (WAP)Protocol (WAP) allow wireless mobile devices to access Internet
Radio Frequency Radio Frequency Identification (RFID)Identification (RFID) uses radio signals to communicatewith a tag placed in an object
Radio Frequency Radio Frequency Identification (RFID)Identification (RFID) uses radio signals to communicatewith a tag placed in an object
Communications Devices
What are examples of communications devices?
Nextp. 298
Common types are dial-up modems, ISDN and DSL modems, cable modems, network cards,
wireless access points, and routers
ISDN and DSL modems send and receive data from ISDN
and DSL lines
Using the Telephone System to Communicate
Public switched telephone network (PSTN)?
Dial-up lineTemporary connection using telephone line for communications
Costs no more than making regular callComputers at any two locations can establish a connection using modems and telephone network
Communications Devices
What is a cable modem?
Nextp. 300 Fig. 8-19
Sends and receives data over cable television network
Much faster than dial-up modem or ISDN
Sometimes called a broadband modem
Communications Devices
What is a network card?
Nextp. 300 Fig. 8-20
Adapter card, PC Card, or compact flash card that enables computer or device to access network
Communications Devices
What are ISDN and DSL modems?
Nextp. 300
Communications devices that send and receive digital ISDN and DSL signals
Communications devices that send and receive digital ISDN and DSL signals
Usually external devices in which one end connects to a telephone line and the other
end connects to a port on the system unit
Usually external devices in which one end connects to a telephone line and the other
end connects to a port on the system unit
Communications Devices
What is a wireless access point?
Nextp. 301 Fig. 8-21
Central communications device that allows computers and devices to transfer data wirelessly among themselves or to wired network
Communications Devices
What is a router? Connects computers and
transmits data to correct destination on network
Routers forward data on Internet using fastest available path
Allow messages to flow between networks
Firewalls
Program or hardware device that filters information coming from Internet connection
If packet of info is flagged, not allowed through
Communications Channel
What is a channel?
Nextp. 303
Transmission media on which data travels in communications system Wire, cable, and other tangible materials used
to send communications signals
Bandwidth is amount of data that can travel over channel
Transmission media are materials capable of carrying one or more signals
Communications Channel
How is a request sent over the Internet using a communications channel?
Nextp. 304 Fig. 8-24
Step 1. The sending device requests information using either a physical transmission media or a wireless transmission media.
Step 2. When the request leaves the ISP, it travels over T1 lines, microwave stations, earth-based stations, and communications satellites until it reaches the Internet backbone.
Step 3. The request travels over T3 lines along the Internet backbone.
Step 4. The Request travels over T1 lines until it reaches the destination network server.
Physical Transmission Media
What are twisted-pair cable and coaxial cable?
Nextp. 305 Fig. 8-25—8-26
Twisted-pair cable is used for telephone systems and network cabling Coaxial cable is often used for cable television wiring
Physical Transmission Media
What is fiber-optic cable?
Nextp. 306 Fig. 8-27
Capable of carrying significantly more data at faster speeds than wire cables
Less susceptible to interference (noise) and, therefore, more secure
Smaller size (thinner and lighter)
Wireless Transmission Media
What is wireless transmission media?
Nextp. 306
Used when inconvenient, impractical, or impossible to install cables
Includes infrared, broadcast radio, cellular radio, microwaves, and communications satellites
Internet Telephony
p. 285 Next
Internet telephonyInternet telephony transmission of phone calls over
data networkSometimes called
Voice over IPVoice over IP
Uses of Computer Communications
What are voice mail and wireless messaging services?
Nextp. 289 Fig. 8-7
Voice mail is voice message converted to digital form Wireless messaging services include:
Text Messaging Instant Messaging Picture Messaging
Collaboration and Groupware
What are collaboration and groupware?
Next
Microsoft Office 2003allows collaboration
Groupware is softwarethat allows peopleto shareinformation
Collaboration is working with other users connected to a server
Public Access Points
Next
Public Internet access point allows wireless connection to Internet in public location
Hot spot
Global Positioning System
Next
Verichip (December, 2001)
Implantable Personal Verification SystemUses RFIDSize of a TicTacImplanted under the skinImmediate ID and retrieval of subscriber supplied registry info