Transcript Modem
Network Devices “What do I need to connect?” Learning Objective: At the end of this topic you should be able to: explain the purpose of the following network components: • switches, • hubs, • network interface cards (NIC), • wireless access points, • routers, • repeaters, • bridges, • servers Local Area Network PCI NIC Local Area Network Local Area Network Network Router Network Interface Card (NIC) PCI NIC Network Interface Card (NIC) Wireless PCMCIA NIC Network Interface Card (NIC) USB Wireless NIC dongle Network Interface Card (NIC) • allows a computer to be physically connected to the network – with a network cable • allows communication to a network from a computer • other devices now have built-in NICs – printers • wireless NICs available – ‘dongles’ – no cables – connects to wireless access point (WAP) • interprets network protocols Network Repeater Network Repeater Repeater • • • • maximum cable length of 180m used to link two cable segments amplifies signals before passing them on allows longer distances between nodes Network Hub Network Hub Network Hub vhjgfhj Network Hub • the central node of a network, – has multiple ports/connections • joins many computers to a network through a single link – a common connection point on a network used to distribute network signals between all nodes • data arrives on one port and is sent to all other ports • each hub can be connected to many network segments • boosts the network signal prior to retransmitting • not as intelligent as a switch Network Switch Network Switch Network Switch • same basic function as a network hub • stores the addresses the devices attached to each port • when data is received via one port, the switch will output the data to the port to which the intended destination is connected Network Router ADSL Router Network Router Wireless Broadband Router Network Router Network Router • communication device to link LAN to WAN • decides on the best path for data through the network – receives data and forwards it to the correct location • can also act as a firewall – blocks unwanted data from entering or leaving the LAN Network Gateway • similar to a network bridge, • links two dissimilar LANs, • passes data packets between LAN segments, • converts between different protocols, • can act as a firewall. Firewall Server • provides central disk storage for network users, • provides network security – by keeping users files separate, – by authenticating users • enables file sharing, – facilitates collaborative working • allows sharing of hardware resources – e.g. printers …. • many networks have multiple servers – file server, print server, mail server, application server, proxy server, back-up server File Server • a computer that stores data for network users – and provides network access to that data • allows access to some of its disk drives – by using the network connection to client computers, • clients use these server disks as if they were 'local' disks • serves user data files – documents, spreadsheets … Print Server • • • • a computer to which one or more printers are connected accepts print jobs from client computers sends the data to the appropriate printer that it manages print jobs are added to an appropriate print queue – print jobs usually handled in the order they are received • restricts access to certain printers – only used by certain users • restricts the number of pages/copies that can be printed • provides reports of who has printed what Proxy Server • holds a store of recently visited sites • passes these onto a user faster than waiting for a WWW download • search cache to see if requested page is there – if not the page is requested over the WWW • downloaded page is then added to the cache – for the next time it’s requested • filtering of sites users are permitted to visit – acts as a firewall • provides access auditing via user log email Server • manages all email for an organisation • receives all incoming emails – allocates emails to appropriate inbox • only allow authorised users to access their own inbox • emails sent by users will be sent by the mail server to: – another user on the LAN (internal email) – via router to a WAN or the Internet • • • • checks all incoming emails for viruses filters out any spam (unsolicited emails) provides a central address book for the orgainisation sets and enforces limits on the size of mailboxes Applications Server • stores software for use across the network 1. stores software so that it can be run from the application server by a client computer saves storage space, memory and processing power on client increases network traffic 2. updates to software downloaded to server and rolled out to clients – anti-virus, OS security patches Back-up Server • centralised back-up of all network data • regular back-ups made without user intervention – type of back-up controlled by network manager • back-up scheduled so that they run automatically – each day, overnight • back-up to magnetic tape, hard drive