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VISUAL SUMMARY Communications and Networks Rev.Confirming Pages VISUAL SUMMARY Communications and Networks COMMUNICATIONS COMMUNICATION CHANNELS Communications is the process of sharing data, pro- Communication channels carry data from one com- grams, and information between two or more com- puter to another. puters. Applications include e-mail, texting, Internet telephones, and electronic commerce. Physical Connections Physical connections use a solid medium to connect Connectivity sending and receiving devices. Connections include Connectivity is a concept related to using computer twisted pair (telephone lines and Ethernet cables), networks to link people and resources. You can link or coaxial cable, and fiber-optic cable. connect to large computers and the Internet, provid- Wireless Connections ing access to extensive information resources. Wireless connections do not use a solid substance to The Wireless Revolution connect devices. Most use radio waves. Mobile devices like smartphones and tablets have • Bluetooth— transmits data over short distances; brought dramatic changes in connectivity and com- widely used for wireless headsets, printers, and munications. These wireless devices are becoming handheld devices. widely used for computer communication. • Wi-Fi (wireless fidelity)— uses high-frequency radio signals; most home and business wireless Communication Systems networks use Wi-Fi. Communication systems transmit data from one loca- • Microwave— line-of-sight communication; used tion to another. Four basic elements are to send data between buildings; longer distances • Sending and receiving devices require microwave stations. • Communication channel (transmission medium) • WiMax (Worldwide Interoperability for Microwave Access)— extends the range of Wi-Fi • Connection (communication) devices networks using microwave connections. • Data transmission specifications • LTE (Long Term Evolution) —currently has similar performance to WiMax; promises to provide greater speed and quality transmissions in the near future. • Satellite —uses microwave relay stations in the sky; GPS (global positioning system) tracks geographic locations. • Infrared —uses light waves over a short distance; line-of-sight communication. 232 CHAPTER 8 oole16864_ch08_210-239.inddle16864_ch08_210-239.indd 223232 110/29/120/29/12 112:432:43 PPMM Rev.Confirming Pages To be a competent end user you need to understand the concepts of connectivity, the wireless revolution, and communication systems. Additionally, you need to know the essential parts of communication technology, including channels, connection devices, data transmission, networks, network architectures, and network types. CONNECTION DEVICES NETWORKS Computer networks connect two or more computers. Some specialized network terms include • Node —any device connected to a network. • Client —node requesting resources. • Server —node providing resources. • Directory server —specialized node that manages resources. • Host —any computer system that can be accessed over a network. • Router —a node that forwards data packets from one network to another network. • Switch —node that coordinates direct flow of data Many communication systems use standard tele- between other nodes. Hub is an older device that phone lines and analog signals. Computers use digital directed flow to all nodes. signals. • NIC (network interface card) —LAN adapter card Modems for connecting to a network. • NOS (network operating system) —controls and Modems modulate and demodulate. Transfer rate is coordinates network operations. measured in megabits per second. Four types are tele- phone, DSL, cable, and wireless (wireless wide area • Network administrator —network specialist network, WWAN). responsible for network operations. Connection Service T1, T3 (DS3), and OC (optical carrier) lines provide NETWORK TYPES support for very high speed, all-digital transmission for large corporations. More affordable technologies Networks can be citywide or even international, using include dial-up, DSL (digital subscriber line), ADSL both wired and wireless connections. (widely used), cable, satellite , and cellular services. • Local area networks (LANs) connect nearby 4G (fourth-generation mobile telecommunications) devices. Network gateways connect networks to promises 10 times faster speeds than 3G. one another. Ethernet is a LAN standard. These LANs are called Ethernet LANs. • Home networks are LANs used in homes. DATA TRANSMISSION • Hotspots provide Internet access typically using Wi-Fi technology. Bandwidth measures a communication channel’s • Wireless LANs (WLANs) use a wireless access width or capacity. Four bandwidths are voiceband point (base station) as a hub. (low bandwidth), medium band, broadband (high- capacity transmissions), and baseband. Protocols are • Personal area networks (PANs) are wireless net- rules for exchanging data. Widely used Internet pro- works for PDAs, cell phones, and other small tocols include http, https, and TCP/IP. IP addresses gadgets. (Internet protocol addresses) are unique numeric • Metropolitan area networks (MANs) link office Internet addresses. DNS (domain name server) con- buildings within a city, spanning up to 100 miles. verts text-based addresses to and from numeric IP • Wide area networks or WANs are the largest type. addresses. Packets are small parts of messages. They span states and countries or form worldwide networks. The Internet is the largest wide area net- work in the world. Communications and Networks 233 oole16864_ch08_210-239.inddle16864_ch08_210-239.indd 223333 110/29/120/29/12 112:432:43 PPMM Rev.Confirming Pages NETWORK ARCHITECTURE ORGANIZATIONAL NETWORKS Internet Technologies Network architecture describes how networks are Internet technologies support effective communica- arranged and resources are shared. tion using intranets and extranets. Topologies • Intranet —private network within an organization; uses browsers, websites, and web pages. Typical A network’s topology describes the physical arrange- applications include electronic telephone directo- ment of a network. ries, e-mail addresses, employee benefit informa- • Bus network— each device is connected to a tion, internal job openings, and much more. common cable called a bus or backbone. • Extranet —like intranet except connects more than • Ring network— each device is connected to two one organization; typically allows suppliers and other devices, forming a ring. others limited access to their networks. • Star network —each device is connected directly to a central network switch; most common type Network Security today. Three technologies commonly used to ensure net- • Tree (hierarchical) network —a central node is work security are firewalls, intrusion detection sys- connected to subordinate nodes forming a treelike tems, and virtual private networks. structure. • Firewall —controls access; all communications • Mesh network —newest; each node has two or pass through proxy server. more connecting nodes. • Intrusion detection systems (IDS) —work with firewalls; use sophisticated statistical techniques Strategies to recognize and disable network attacks. Every network has a strategy, or way of sharing infor- • Virtual private network (VPN) —creates secure mation and resources. Common network strategies private connection between remote user and orga- include client/server and peer-to-peer. nization’s internal network. • Client/server (hierarchical) network —central com- puters coordinate and supply services to other nodes; based on specialization of nodes; widely CAREERS IN IT used on the Internet; able to handle very large net- works efficiently; powerful network management Network administrators manage a company’s software available. LAN and WAN networks. Bachelor’s or specialized • Peer-to-peer network —nodes have equal authority advanced associate’s degree in computer science, and act as both clients and servers; widely used to computer technology, or information systems and share games, movies, and music over the Internet; practical networking experience required. Salary easy to set up and use; lacks security controls. range is $46,000 to $84,000. 234 CHAPTER 8 oole16864_ch08_210-239.inddle16864_ch08_210-239.indd 223434 110/29/120/29/12 112:432:43 PPMM Rev.Confirming Pages KEY TERMS 1G (first-generation downlink (215) optical carrier (OC) (217) mobile telecommuni- DS3 (217) packet (220) cations) (218) Ethernet (223) peer-to-peer (P2P) 2G (second-generation Ethernet cable (214) network (227) mobile telecommuni- extranet (227) personal area network cations) (218) fiber-optic cable (214) (PAN) (224) 3G (third-generation firewall (228) protocol (220) mobile telecommuni- global positioning system proxy server (228) cations) (218) (GPS) (215) ring network (225) 4G (fourth-generation hierarchical network (226) router (222) mobile telecommuni- home network (223) satellite (215) cations) (218) host (222) satellite connection analog signal (216) hotspot (224) service (217) asymmetric digital subscriber http (hypertext transfer server (221) line (ADSL) (217) protocol) (220) star network (225) backbone (225) https (hypertext transfer strategy (226) bandwidth (218) protocol secure) (220) switch (222) base station (223) hub (222) T1 (217) baseband (218) infrared (216) T3 (217) Bluetooth (215) intranet (227) telephone line (214) broadband (218) intrusion detection system telephone modem (216) bus (225) (IDS) (228) topology (225) bus network (225) IP address (Internet transfer rate (216) cable modem (217) protocol address) (220) transmission control cable
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