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Understanding the Basic of Computer Network: Networking Hardware and Network Opera;ng System Heng Sovannarith [email protected] Networking Hardware • • • • • • • • File Servers Worksta;ons Network Interface Card Repeaters Hub Switch Bridges Router Introduc;on • Networking hardware includes all computers, peripherals, interface cards and other equipment needed to perform data-‐ processing and communica;ons within the network. File/Network Server • One or more network servers is a part of nearly every local area network. • These are very fast computers with a large amount of RAM and storage space, along with a one or more fast network interface card(s). • The network opera;ng system provides tools to share server resources and informa;on with network users. File/Network Server (cont.) • A sophis;cated permissions-‐handling system is included, so that access to sensi;ve informa;on can be carefully tailored to the needs of the users. • For small networks, a singe network server may provide access control, file sharing, printer sharing, email, database, and other services. File/Network Server Worksta;ons • Computers that humans use are broadly categorized as worksta;ons. • A typical worksta;on is a computer that is configured with a network interface card, networking soSware, and the appropriate cables. • Worksta;ons do not necessarily need large storage hard drives, because files can be saved on the file server. • Almost any computer can serve as a network worksta;on. Network Interface Cards • The network interface card (NIC) provides the physical connec;on between the network and the computer worksta;on. • Network interface cards are a major factor in determining the speed and performance of a network. • It is a good idea to use the fastest network card available for the type of worksta;on you are using. • The most common network interface connec;ons are Ethernet cards and wireless adapters. Network Interface Cards (cont.) • Ethernet card can be used with coaxial, twisted pair, or fiber op;cs cable. • Wireless adapters are found in most portable devices, such as laptops, smart phones, and tablet devices. Network Interface Cards (cont.) Repeater • Since a signal loses strength as it passes along a cable, it is oSen necessary to boost the signal with a device called a repeater. • The repeater electrically amplifies the signal it receives and rebroadcasts it. • They are used when the total length of your network cable exceeds the standards set for the type of cable being used. Repeater (cont.) • Func;ons at the Physical Layer of the OSI model • A mul;-‐port repeater is known as a Hub • Connects segments of the same network, even if they use different media • Repeater Hub • Allows the mul;ple connec;on of devices • In reality a Hub is a Repeater with mul;ple ports • Func;ons in a similar manner to a Repeater • Works at the Physical Layer of the OSI model • Hubs do not manage any of the traffic that comes through them. Any packet entering a port is broadcast out or "repeated" on every other port, except for the port of entry. Hub (cont.) hub hub hub hub Switch • An switch is a device that provides a central connec;on point for cables from worksta;ons, servers, and peripherals. • Modern switches build a port map of all IP address which respond on each port, and only broadcasts on all ports when it doesn't have a packet's target IP address already in its port map. • An switch operates at Layer 2 (the data link layer) of the OSI model. • Most large networks use switches rather than hubs to connect computers within the same subnet. Switch (cont.) Bridge • A bridge is a device that connects a local area network (LAN) to another local area network that uses the same protocol (for example, Ethernet or Token Ring). • It looks at the des;na;on of the packet before sending. If the des;na;on address is not on the other side of the bridge it will not transmit the data. • A bridge only has one incoming and one outgoing port. • Bridges are typically used to separate parts of a network that do not need to communicate regularly, but s;ll need to be connected. Bridge (cont.) Bridge A Transmits to C, bridge will not pass it to Segment B Segment A A D B C G Transmits to B, bridge will pass it to Segment A Segment B E H F G Router • A router is similar in a switch in that it forwards packets based on address. • But, instead of the MAC address that a switch uses, a router can use the IP address. • This allows the network to go across different protocols. • A router is connected to two or more data lines from different networks. • An Router operates at Layer 3 (the network layer) of the OSI model. Router (cont.) • Work in LAN, MAN and WAN environments • Can interconnect different networks – Ethernet with Token Ring • Allows access to resources by selec;ng the best path • Two primary func;ons – to determine the ‘best path’ and to share details of routes with other routers Router (cont.) • Two primary func;ons – to determine the ‘best path’ and to share details of routes with other routers • Rou;ng Table – a database which keeps track of the routes to networks and the associated costs Router (cont.) • Sta;c Rou;ng – routes are manually configured by a network administrator • Dynamic Rou;ng – adjust automa;cally to changes in network topology, and informa;on it receives from other routers • Rou;ng Protocol – uses a special algorithm to route data across a network Firewall • A firewall is a networking device that is installed at the entrance to a LAN when connec;ng a networks together, par;cularly when connec;ng a private network to a public network, such as the internet. • Firewalls are either hardware or soSware, depending on their intended use. Network Opera;ng System • Unlike opera;ng systems, such as Windows, that are designed for single users to control one computer, network opera;ng systems (NOS) coordinate the ac;vi;es of mul;ple computers across a network. • The network opera;ng system acts as a director to keep the network running smoothly. • The two major types of network opera;ng systems are: – Peer to Peer – Client/Server Peer-‐to-‐Peer • Peer-‐to-‐peer network opera;ng systems allow users to share resources and files located on their computers and to access shared resources found on other computers. • However, they do not have a file server or a centralized management source • In a peer-‐to-‐peer network, all computers are considered equal; they all have the same abili;es to use the resources available on the network. Peer-‐to-‐Peer (cont.) • Peer-‐to-‐peer networks are designed primarily for small to medium local area networks. • Nearly all modern desktop opera;ng systems, such as Macintosh OSX, Linux, and Windows, can func;on as peer-‐to-‐peer network opera;ng systems. • • Peer-‐to-‐Peer (cont.) • Advantages of a peer-‐to-‐peer network: – Less ini;al expense -‐ No need for a server. – Setup -‐ An opera;ng system (such as Windows XP) already in place may only need to be reconfigured for peer-‐to-‐peer opera;ons. • Disadvantages of a peer-‐to-‐peer network: – Decentralized -‐ No central loca;on for files and applica;ons. – Security -‐ Does not provide the security available on a client/server network. Client/Server • Client/server network opera;ng systems allow the network to centralize func;ons and applica;ons in one or more file servers • The file servers become the heart of the system, providing access to resources and providing security. • Individual worksta;ons (clients) have access to the resources available on the file servers. • UNIX/Linux and the MicrosoS family of Windows Servers are examples of client/server network opera;ng systems. Client/Server (cont.) Client/Server (cont.) • Advantages of a client/server network: – Centralized -‐ Resources and data security are controlled through the server. – Scalability -‐ Any or all elements can be replaced individually as needs increase. – Flexibility -‐ New technology can be easily integrated into system. – Interoperability -‐ All components (client/network/ server) work together. – Accessibility -‐ Server can be accessed remotely and across mul;ple plaeorms Client/Server (cont.) • Disadvantages of a client/server network: – Expense -‐ Requires ini;al investment in dedicated server. – Maintenance -‐ Large networks will require a staff to ensure efficient opera;on. – Dependence -‐ When server goes down, opera;ons will cease across the network. Network Opera;ng System SoSware • some of the more popular peer-‐to-‐peer and client/server network opera;ng systems: – Macintosh OS X – MicrosoS Windows Server – UNIX/Linux