Computer Networks – an overview 1

2 Computer Networks Advantages of a network Advantages of a network Client/server and peer-to-peer networks Client/server and peer-to-peer networks Classifications of client/server networks Classifications of client/server networks Client/server network components Client/server network components Types of servers Types of servers Network topologies Network topologies

3 Topics Types of transmission media Types of transmission media Network software Network software Network adapters Network adapters Moving data in a client/server network Moving data in a client/server network

4 Networking Advantages Networks: Networks: Increase productivityIncrease productivity Enable the sharing of resourcesEnable the sharing of resources Facilitate Internet connectivityFacilitate Internet connectivity

5 Client/Server Networks Server based network: Server based network: ClientsClients ServersServers Data flows efficiently Data flows efficiently Servers respond to requests from clients Servers respond to requests from clients Servers perform specific tasks Servers perform specific tasks Scalable network Scalable network

6 Classifications of Client/Server Networks LAN: LAN: Local area networkLocal area network Computers linked together over a small geographic regionComputers linked together over a small geographic region WAN: WAN: Wide area networkWide area network Computers linked together over large diverse geographic locationsComputers linked together over large diverse geographic locations MAN: MAN: Metropolitan area networkMetropolitan area network Computers linked together within a city or countyComputers linked together within a city or county

7 Classifications of Client/Server Networks PAN: PAN: Personal area networkPersonal area network Wireless devices connected in close proximity to each otherWireless devices connected in close proximity to each other Intranet: Intranet: Private corporate networkPrivate corporate network

8 Constructing Client/Server Networks Servers Servers Servers Network topologies Network topologies Network topologies Network topologies Transmission media Transmission media Transmission media Transmission media Network operating system (NOS) Network operating system (NOS) Network operating system (NOS) Network operating system (NOS) Network adapters Network adapters Network adapters Network adapters Network navigation devices Network navigation devices Network navigation devices Network navigation devices

9 Servers Number and type of servers depend on network size and workload Number and type of servers depend on network size and workload Dedicated server: Dedicated server: Perform one specific functionPerform one specific function Authentication server: Authentication server: Keeps track of network logins and services availableKeeps track of network logins and services available File server: File server: Store and manage filesStore and manage files

10 Dedicated Servers Print server: Print server: Manages client-requested printing jobsManages client-requested printing jobs Creates print queue (prioritizes print jobs)Creates print queue (prioritizes print jobs) Applications server: Applications server: Acts as a storage area for application softwareActs as a storage area for application software Database server: Database server: Provides clients with access to database informationProvides clients with access to database information server: server: Process and deliver in-coming and outgoing e- mailProcess and deliver in-coming and outgoing e- mail

11 Dedicated Servers Communications server: Communications server: Handles communications between networks including the InternetHandles communications between networks including the Internet Web server: Web server: Hosts a Web site available through the InternetHosts a Web site available through the Internet

12 Network Topologies The physical layout of computers, transmission media, and other components The physical layout of computers, transmission media, and other components Types of network topologies include: Types of network topologies include: Bus topologyBus topologyBus topologyBus topology Ring topologyRing topologyRing topologyRing topology Star topologyStar topologyStar topologyStar topology

13 Bus Topology All nodes are connected in sequence on a single cable All nodes are connected in sequence on a single cable Used most often on peer-to-peer networks Used most often on peer-to-peer networks Networked computers communicate with each other Networked computers communicate with each other One computer transmits data at a time: One computer transmits data at a time: Access methods avoid data collisionsAccess methods avoid data collisions Data is transmitted in “packets”Data is transmitted in “packets”

14 Ring Topology Nodes are laid out in a ring Nodes are laid out in a ring Token (data packet) flows in one direction from device to device Token (data packet) flows in one direction from device to device

15 Star Topology Nodes connect to a central communications device (hub/switch) Nodes connect to a central communications device (hub/switch) A node sends a signal to the hub which retransmits it to the other nodes A node sends a signal to the hub which retransmits it to the other nodes A node accepts the signal addressed to it A node accepts the signal addressed to it

16 Avoiding Data Collisions on a Star Network

17 Transmission Media The routes data takes to flow between devices on a network: The routes data takes to flow between devices on a network: Wired Wired Wired Wireless: Wireless: Wireless Fidelity (Wi-Fi)Wireless Fidelity (Wi-Fi) Uses radio wavesUses radio waves standard standard

18 Choosing a Cable Maximum run length Maximum run length Bandwidth Bandwidth Bend radius Bend radius Cable cost Cable cost Installation costs Installation costs Susceptibility to interference Susceptibility to interference Signal transmission methods Signal transmission methods

19 Twisted Pair Cable Pairs of copper wire twisted around each other Pairs of copper wire twisted around each other Twists make the wires less susceptible to interference Twists make the wires less susceptible to interference Shielded twisted pair (STP) Shielded twisted pair (STP) Layer of foil shieldingLayer of foil shielding Unshielded twisted pair (UTP) Unshielded twisted pair (UTP) Cat 5ECat 5E Bandwidth 1Gbps Bandwidth 1Gbps Cat 6Cat 6 Bandwidth 200 Mbps Bandwidth 200 Mbps

20 Coaxial Cable Four components: Four components: Copper coreCopper core Nonconductive insulating materialNonconductive insulating material Braided metalBraided metal Plastic coverPlastic cover

21 Fiber-Optic Cable Components include: Components include: Glass or plastic fibersGlass or plastic fibers CladdingCladding Outer jacketOuter jacket Uses light impulses to transmit data Uses light impulses to transmit data Immune to interference Immune to interference

22 Network Operating Systems (NOS) Provide the protocol that controls the communication between devices on the network Provide the protocol that controls the communication between devices on the network Major network operating systems: Major network operating systems: Windows Server XXWindows Server XX UNIXUNIX Novell NetWareNovell NetWare

23 Network Adapters Devices that enable computers to communicate on a network Devices that enable computers to communicate on a network Network interface cards (NICs): Network interface cards (NICs): Generate network transmission signalsGenerate network transmission signals Create data packetsCreate data packets Act as information gatekeepersAct as information gatekeepers Ethernet compliantEthernet compliant Wireless NICsWireless NICs

24 Network Navigation Devices Media Access Control (MAC) address: Media Access Control (MAC) address: Six 2-digit numbers (01:40:87:44:79:A5)Six 2-digit numbers (01:40:87:44:79:A5) Physical address of network adapterPhysical address of network adapter Internal network identificationInternal network identification Repeaters and Hubs: Repeaters and Hubs: Amplify signals and retransmit themAmplify signals and retransmit them Switches and Bridges: Switches and Bridges: Send data on a specific route through the networkSend data on a specific route through the network Bridges send data between collision domainsBridges send data between collision domains Routers: Routers: Send information between two networksSend information between two networks