Chapter 8 Computer Networks

Networking and Communications Applications Wireless phones Cellular phones Satellite phones Paging and messaging Global positioning systems (GPSs) Satellite radio

Networking and Communications Applications, Cont’d. Online conferencing (online meetings) Videoconferencing Web conferencing Collaborative computing Telecommuting Telemedicine

What Is a Network and How Does it Transmit Data? Computer network—a collection of computers and other hardware connected together to share data, hardware, software, programs, and facilitate electronic communication.

Data Transmission Characteristics Analog (continuous wave) vs. digital (discreet 0s and 1s). Bandwidth and speed (higher bandwidth allows more data to travel at the same time). Serial vs. parallel transmission.

Data Transmission Characteristics, Cont’d. Transmission directions Simplex transmission (one way only). Half-duplex transmission (one way at a time). Full-duplex transmission (both ways at the same time).

Data Transmission Characteristics, Cont’d. Transmission timing Synchronous transmission Asynchronous transmission Isochronous transmission

Wired vs. Wireless Connections With a wired network connection, the PC is physically cabled to the network. Common in schools, business, and government facilities. Wireless network connections allow great freedom regarding where users can use their PCs. Increasingly common in homes, businesses, and wireless public hot spots (e.g. Starbucks).

Wired Network Transmission Media Twisted-pair cable Pairs of wires twisted together. Used for telephone and network connections. Coaxial cable Thick center wire. Used for cable TV and network connections. Fiber-optic cable Glass or fiber strands through which light can pass. Used for high-speed communications.

Wireless Network Transmission Media Broadcast radio transmissions (FM and AM radio broadcasts, short-range networking and wireless devices). Microwave and satellite transmissions. Microwave stations Communications satellites Cellular radio transmissions.

Network Topologies Star Bus Ring Combination

Network Architectures Client-server networks Client—makes requests of servers. Server—fulfills client requests (for files, programs, Web pages, etc.). Peer-to-peer networks (all computers at the same level) Often takes place via the Internet.

LANs, WANs, and Other Types of Networks Personal area networks (PANs) Local area networks (LANs) Metropolitan area networks (MANs) Wide area networks (WANs) Internet

LANs, WANs, and Other Types of Networks, Cont’d. Intranets and extranets Virtual private networks (VPNs) Storage area networks (SANs)

Networking Hardware Network adapters, also called network interface cards (NICs). Needed to connect PC to network. Come in a variety of formats (internal or external, wireless or wired, PC card, USB, etc.).

Networking Hardware, Cont’d. Modems (used to connect PC to the Internet) Conventional dial-up ISDN DSL Cable Satellite

Networking Hardware, Cont’d. Hubs, switches, and routers Wireless access points Gateways and bridges Repeaters Multiplexers and concentrators

Communications Protocols Communications protocol—an agreed-upon standard for transmitting data between two devices on a network. Common wired protocols are Ethernet, Token Ring, and TCP/IP. Common wireless protocols are 802.11 (Wi-Fi), Bluetooth, and WAP.

Ethernet Typically used with wired LANs. Utilizes a set of procedures (CSMA/CD) to send data and make sure it arrives. Traditional (10Base-T) Ethernet networks run at 10 Mbps; newer 100 Mbps and 1 Gbps versions are now available.

Token Ring Usually used with a ring network topology and utilizes a token to send and retrieve data.

TCP/IP The protocol used with the Internet also increasingly being used with LANs. Sends data in packets.

802.11 (Wi-Fi) and Bluetooth 802.11 (Wi-Fi for wireless fidelity)—a family of wireless networking standards. 802.11b is the original standard (11 Mbps). 802.11g is faster (54 Mbps) and expected to eventually replace 802.11b. Newer versions are in development. Bluetooth is a standard for low-cost, short-range, wireless connections between Bluetooth-enabled devices.

Other Networking Protocols Wireless Application Protocol (WAP)—for Web content delivered to smart phones and other mobile devices. IrDA—used for short range infrared data transfers. Phoneline (Home PNA) Powerline Ultra Wideband (UWB)—for home multimedia delivery.

Network Security Issues Unauthorized access and unauthorized use. Hacking War driving Protecting against unauthorized access and use. Possessed knowledge systems (e.g. passwords). Possessed object systems (e.g. cards or badges). Biometric systems (e.g fingerprint scanners or face readers). Firewalls and other protective software.

Network Security Issues, Cont’d. Computer sabotage Computer viruses and other types of malware (e.g. computer worms and Trojan horses). Denial of service (DoS) attacks. Malicious spamming. Data or program alteration.

Network Security Issues, Cont’d. Protecting against computer sabotage. Use up-to-date antivirus and firewall software. Limit sharing disks and other removable storage media. Only download programs from reputable Web sites. Only open e-mail attachments that aren’t executable and are from people you know. Regularly download and install the latest security patches available for your e-mail program and browser.

Summary Networking and communications applications What is a network and how does it transmit data? Types of networks Networking hardware Communications protocols Network security issues