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NETWORKING FUNDAMENTALS Network+ Guide to Networks, 4e 2 Why Use Networks? • Network: group of computers and other devices that are connected by some type of transmission media • Advantages of using networks over standalone computers: – Networks enable multiple users to share the network’s resources (devices and data) – Networks allow you to manage, or administer, resources on multiple computers from a central location Network+ Guide to Networks, 4e 3 NETWORK ARCHITECTURE Peer-to-peer Networks • Every computer can communicate directly with every other computer • By default, no computer has more authority than another • Every computer is capable of sending and receiving information to and from every other computer Network+ Guide to Networks, 4e 4 Peer-to-peer Networks Figure 1-1: Resource sharing on a simple peer-to-peer network Network+ Guide to Networks, 4e 5 Client/Server Networks • Server: central computer used to facilitate communication and resource sharing between other computers on the network (called clients) • Client/server network: uses a server to enable clients to share data, data storage space, and devices • To function as a server, a computer must be running a network operating system (NOS) Network+ Guide to Networks, 4e 6 Client/Server Networks (continued) Figure 1-2: Resource sharing on a client/server network Network+ Guide to Networks, 4e 7 Client/Server Networks (continued) • Advantages of using client/server networks over peer-to-peer networks: – User logon accounts and passwords can be assigned in one place – Access to multiple shared resources can be centrally granted to a single user or groups of users – Problems can be tracked, diagnosed, and often fixed from one location Network+ Guide to Networks, 4e 8 Client/Server Networks (continued) • Advantages of using client/server networks over peer-to-peer networks (continued): – Servers are optimized to handle heavy processing loads and dedicated to handling requests from clients, enabling faster response time – Because of their efficient processing and larger disk storage, servers can connect more than a handful of computers on a network Network+ Guide to Networks, 4e 9 TYPES OF NETWORKS • Local area network (LAN): confined to a relatively small space, such as a building or an office • Metropolitan area network (MAN): larger than a LAN; connects clients and servers from multiple buildings • Wide area network (WAN): connects two or more geographically distinct LANs or MANs Network+ Guide to Networks, 4e 10 LANs, MANs, and WANs (continued) Figure 1-4: A simple WAN Network+ Guide to Networks, 4e 11 BENEFITS OF A NETWORK • Information sharing: Authorized users can use other computers on the network to access and share information and data. This could include special group projects, databases, etc. • Hardware sharing: One device connected to a network, such as a printer or scanner, can be shared by many users. • Software sharing: Instead of purchasing and installing a software program on each computer, it can be installed on the server. All of the users can then access the program from a single location. • Collaborative environment: Users can work together on group projects by combining the power and capabilities of diverse equipment. Network+ Guide to Networks, 4e 12 HOW ARE NETWORKS CATEGORIZED? • Networks are usually classified using three properties: • Topology • Protocol • Architecture Network+ Guide to Networks, 4e 13 NETWORK TOPOLOGIES • Network Topology (or layout) – refers to the way computers and peripherals are configured to form networks – Bus topology – all computers are linked by a single line of cable – Star topology – multiple computers and peripheral devices are linked to a central computer, called a host – Ring topology – each computer or workstation is connected to two other computers, with the entire network forming a circle – Hybrid topology – combine network layout types to meet their needs Network+ Guide to Networks, 4e 14 NETWORK/COMMUNICATION PROTOCOLS • A protocol is simply an agreed-on set of rules and procedures for transmitting data between two or more devices. • Features determined by the protocol are: – How the sending device indicates it has finished sending the message. – How the receiving device indicates it has received the message. – The type of error checking to be used. Network+ Guide to Networks, 4e 15 Signals and Protocols • A data network is a group of computers connected by a network medium. • The network medium carries signals between computers. • Signals reduce complex information to the simplest possible form. • Computers communicate by using a language called a protocol. Network+ Guide to Networks, 4e 16 Protocol Services • • • • • • • Packet acknowledgment Segmentation Flow control Error detection Error correction Data compression Data encryption Network+ Guide to Networks, 4e 17 The OSI Reference Model Network+ Guide to Networks, 4e 18 Data Encapsulation Network+ Guide to Networks, 4e 19 The OSI Reference Model Network+ Guide to Networks, 4e 20 NETWORKING HARDWARE AND SOFTWARE • Hub – electronic device (with a number of ports) used in a LAN to link groups of computers • Repeaters (also called amplifiers) – electronic devices that receive signals and amplify and send them along the network • Routers - electronic devices used to ensure messages are sent to their intended destinations • Gateway – consists of hardware and/or software that allows communications between dissimilar networks • Bridge – consists of hardware and/or software that allows communication between two similar networks Network+ Guide to Networks, 4e 21 REPEATERS • A common problem in the networking world is that of weakening electrical signals. Electrical signals traveling through wires (such as copper wires used in most networks) This effect limits the lengths of the cable that can be used. when there is a need to connect two computers at a larger distance. • A repeater is connected to two cable segments. Any electrical signal reaching the repeater from one segment, will be amplified and retransmitted to the other segment. An illustration of a repeater at work The electrical signal entering the repeater at one end is weakened.The repeater amplifies the electrical signals and resends the data. 22 ROUTERS • Routers connect two or more networks and forward data packets between them. When data arrives from one of the segments, the router decides, according to it's routing table, to which segment to forward that data. Network+ Guide to Networks, 4e 23 MODEMS • An illustration of data sent using a modem and a regular telephone line. • A modem is a device that converts digital data A modem is a device that converts digital originatingdata from a terminal computer, to analog originating from or a terminal or signals used by voice communication networks such as computer, to analog signals used by voice communication such asmodems the the telephone system. networks At one end, convert the telephone system. tones At one end, digital pulses to audible andmodems convert audio tones convert the digital pulses to audible tones back to digital pulses at the other. and convert audio tones back to digital pulses at the other. 24 EXAMPLE OF FIREWALL Firewalls are systems that establish access control policies among networks. They can block information from entering a network or from getting out of that network, they can permit different users to perform different kinds of operations, according to the user's authorizations. Network+ Guide to Networks, 4e 25 Elements Common to Client/Server Networks Network+ Guide to Networks, 4e 26 Elements Common to Client/Server Networks Figure 1-8: Examples of network transmission media Network+ Guide to Networks, 4e 27 How Networks Are Used • Network services: functions provided by a network • File services – Capability of a server to share data files, applications, and disk storage space – File server • Print services: used to share printers across a network Network+ Guide to Networks, 4e 28 How Networks Are Used • Communications services – Allow remote users to connect to the network – Remote access server (also known as communications server or access server) • Mail services – Coordinate the storage and transfer of e-mail between users on a network – Mail server Network+ Guide to Networks, 4e 29 How Networks Are Used • Internet services – Supplying Web pages, file transfer capabilities, Internet addressing schemes, security filters, and a means for directly logging on to other computers on the Internet – Web server • Management services: centrally administer management tasks on the network – Traffic monitoring and control – Load balancing Network+ Guide to Networks, 4e 30