Computers Are Your Future Chapter 8 Computers Are

Computers Are Your Future Chapter 8 Computers Are Your Future © 2008 Prentice-Hall, Inc.

Computers Are Your Future Chapter 8 Networks: Communicating and Sharing Resources © 2008 Prentice-Hall, Inc. Slide 2

Computers Are Your Future Chapter 8 Network Fundamentals ØA computer network consists of two or more computers linked together to exchange data and share resources. • LAN – local area network (small geographic area) • WAN – wide area network (large geographic area) © 2008 Prentice-Hall, Inc. Slide 3

Computers Are Your Future Chapter 8 Communication Devices Ø Convert data into signals. Ø Transform data from analog into digital signals and back. Ø Computers, modems, routers, switches, wireless access points, and network interface cards are all communication devices. © 2008 Prentice-Hall, Inc. computers modems routers switches Network Interface Cards Slide 4

Computers Are Your Future Chapter 8 Communication Devices Workstations – computer connected to a network Ø Called clients Ø Contains a network interface card (NIC) © 2008 Prentice-Hall, Inc. Slide 5

Computers Are Your Future Chapter 8 Communication Devices Routers – connect two or more LANs or WANs Ø Can determine the best path to route data. Ø LANs often use switches which are similar to routers. © 2008 Prentice-Hall, Inc. Slide 6

Computers Are Your Future Chapter 8 Communication Devices File server Ø High capacity, high speed computer Ø Large hard drive Ø Contains a network operating system (NOS) © 2008 Prentice-Hall, Inc. Slide 7

Computers Are Your Future Chapter 8 Network Fundamentals Network administrators Ø Install Ø Maintain Ø Support Ø Interact with users Ø Troubleshoot problems © 2008 Prentice-Hall, Inc. Slide 8

Computers Are Your Future Chapter 8 Advantages of Networks Ø Reduced hardware costs Ø Application sharing Ø Sharing information resources Ø Centralized data management Ø Connecting people © 2008 Prentice-Hall, Inc. Slide 9

Computers Are Your Future Chapter 8 Disadvantages of Networks Ø Loss of autonomy Ø Lack of privacy Ø Security threats Ø Loss of productivity © 2008 Prentice-Hall, Inc. Slide 10

Computers Are Your Future Chapter 8 Local Area Networks (LANs) Ø Network access is controlled by a network administrator. Ø Users can access software, data, and peripherals. Ø LANs require special hardware and software. Ø Computers connected to a LAN are called workstations or nodes. Ø Types of LANs: • Peer-to-peer • Client-server © 2008 Prentice-Hall, Inc. Slide 11

Computers Are Your Future Chapter 8 LAN Hardware and Software Networking Hardware Networking Software ØNetwork interface card ØOperating system that (NIC) – Provides the connection between the computer and the network ØInserted into a computer’s expansion slot supports networking (Unix, Linux, Windows, Mac OS) ØAdditional system software NIC © 2008 Prentice-Hall, Inc. Slide 12

Computers Are Your Future Chapter 8 Peer-to-Peer Networks Ø All computers on the network are treated as equal. Ø There are no file servers. Ø Users decide which files and peripherals to share. Ø Peer-to peer is not suited for networks with many computers. Ø Peer-to-peer is easy to set up; example: home networks. © 2008 Prentice-Hall, Inc. Slide 13

Computers Are Your Future Chapter 8 Client-Server Networks Ø Typical corporate networks are client-server. Ø Client-server requires various topologies or physical layouts. Ø The network requires file servers, networked computers (clients), and a network operating system (NOS). Ø Clients send requests to servers for programs and data, and to access peripherals. © 2008 Prentice-Hall, Inc. Slide 14

Computers Are Your Future Chapter 8 LAN Topologies Ø The physical layout of a LAN is called its topology. Ø Topologies resolve the problem of contention, which occurs when multiple users try to access the LAN at the same time. • Collisions or corrupt data occur when different computers use the network at the same time. Ø Click to see examples. Bus Ring Startopology • • • All workstations Called Contains a daisy a hubchain orare central attached wiring in a Every workstation concentrator circular arrangement is connected to a single Easy A special tocable add unit workstations of data called a Resolves token travels collisions aroundthrough the ring contention management Workstations can only transmit data Difficult when theytopossess add workstations a token © 2008 Prentice-Hall, Inc. Slide 15

Computers Are Your Future Chapter 8 Protocols Ø Protocols are fixed, formalized standards that specify how computers can communicate over a network. Ø A protocol suite is the total package of protocols that specify how a network functions. © 2008 Prentice-Hall, Inc. Slide 16

Computers Are Your Future Chapter 8 Network Layers user layer physical media receiving sending protocol user stack physical media Ø Network architecture is the overall design of a network. Ø The network design is divided into layers, each of which has a function separate from that of the other layers. Ø The protocol stack is the vertical (top to bottom) arrangement of the layers; each layer is governed by its own set of protocols. © 2008 Prentice-Hall, Inc. Slide 17

Computers Are Your Future Chapter 8 Ethernet Protocol Ø Ethernet uses a protocol called Carrier Sense Multiple Access/ Collision Detection (CSMA/CD) Ø CSMA/CD works as follow: 1. Sender senses the media for a fixed time 2. Sender computer place a data unit with fixed size (packet), the packet contains the address of the receiver plus the data, now two possibilities 3. If no other computer were sending at the same time, The packet will reach the destination, the distention will confirm by sending an acknowledgement back to the sender. If another computer was sending at the same time, collision will occur and both packets will not reach their destinations. 4. As a result of collision, no acknowledgement is sent to the sender. The sender in this case will assume the packet has not reached the distention and resend it again after waiting for some random time interval. © 2008 Prentice-Hall, Inc. Slide 18

Computers Are Your Future Chapter 8 Ethernet Protocol No collision © 2008 Prentice-Hall, Inc. Slide 19

Computers Are Your Future Chapter 8 Ethernet Protocol C A B A and C transmit at athe same time => Collision collision avoidance A and C will re-transmit after random © 2008 Prentice-Hall, Inc. Slide 20

Computers Are Your Future Chapter 8 Wi-Fi Ø Wireless-fidelity Ø Wireless LAN Ø Uses a central access point Ø Advantages • Fast (11 Mbps) • Reliable • Long range • Integrates with existing networks © 2008 Prentice-Hall, Inc. Slide 21

Computers Are Your Future Chapter 8 Wide Area Networks (WANs) WANs are similar to long-distance telephone systems. Ø They have a local access number called a point of presence (POP). Ø They contain long-distance trunk lines called backbones. © 2008 Prentice-Hall, Inc. Slide 22

Computers Are Your Future Chapter 8 Backbones Ø Backbones, high-capacity transmission lines, can be regional, continental, or transcontinental. Ø Internet backbones can carry 2. 5 gigabits of data per second. © 2008 Prentice-Hall, Inc. Slide 23

Computers Are Your Future Chapter 8 The internet protocol ü The internet protocols collectively called Transmission Control Protocol/Internet Protocol TCP/IP ü IP enables direct and immediate contact between one computer another. A computer can contact another by dialing the other computer’s IP address. ü TCP defines how the connection is established between 2 computers © 2008 Prentice-Hall, Inc. Slide 24

Computers Are Your Future Chapter 8 TCP/IP Protocol © 2008 Prentice-Hall, Inc. Slide 25

Computers Are Your Future Chapter 8 Switching and Routing Techniques Packet switching Circuit switching Ø Networks create an end-to -end circuit between the sending and receiving computers. Ø Electronic switches establish and maintain the connection. © 2008 Prentice-Hall, Inc. Ø Outgoing messages are divided into fixed-size data units called packets. Ø Packets are numbered and addressed to the receiving computer. Ø Routers examine the packets and send them to their destination. Slide 26

Computers Are Your Future Chapter 8 Circuit Switching © 2008 Prentice-Hall, Inc. Slide 27

Computers Are Your Future Chapter 8 Packet Switching © 2008 Prentice-Hall, Inc. Slide 28

Computers Are Your Future Chapter 8 Advantages and Disadvantages of Circuit and Packet Switching Advantages Disadvantages Circuit switching Voice and real-time transmission No delivery delays Costly A direct electrical connection between the computers is required Packet switching Efficient, less expensive, and reliable Will function if part of the network is down Delays in receiving packets Not ideal for real-time voice communication © 2008 Prentice-Hall, Inc. Slide 29

Computers Are Your Future Chapter 8 WAN Protocols Ø X. 25 is the oldest packet switching protocol; it is used by automated teller machines and credit card authorization devices. Ø New protocols designed for digital lines and faster data transfer rates are: • Switched Multimegabit Data Service (SMDS) • Asynchronous Transfer Mode (ATM) © 2008 Prentice-Hall, Inc. Slide 30

Computers Are Your Future Chapter 8 WAN Applications LAN-to-LAN Ø WANs are used to connect LANs at two or more geographic locations. Ø Companies use WANs to connect their branches to one network system. © 2008 Prentice-Hall, Inc. Transaction Acquisition Ø Information about transactions is instantly relayed to the corporate headquarters. Ø Point-of-sale (POS) terminals relay transactions to central computers through WANs. Slide 31

Computers Are Your Future Chapter 8 Summary Ø Computer networks link two or more computers to exchange data and share resources. Ø Two types of computer networks: • Local area network (LAN) • Wide area network (WAN) Ø Computer networks: • Reduce hardware costs • Enable users to share applications • Provide a means to pool an organization’s data • Foster teamwork Ø Peer-to-peer uses no file server. © 2008 Prentice-Hall, Inc. Slide 32

Computers Are Your Future Chapter 8 Summary continued Ø Network topologies are the physical layout of a LAN. Ø LAN topologies include: • Bus topology • Star topology • Ring topology Ø Protocols define how devices communicate with each other. Ø Ethernet is the most widely used LAN protocol. © 2008 Prentice-Hall, Inc. Slide 33

Computers Are Your Future Chapter 8 Summary (continued) Ø Point of presence (POP) is a WAN connection point. Ø Circuit switching creates permanent end-toend circuit that is optimal for voice and realtime data. Ø Packet switching does not require a permanent switched circuit. © 2008 Prentice-Hall, Inc. Slide 34