1. 1 Network Strategy By Mr J. Sloan

2. Ideas Protocol WAN LAN Node What is a… Workstation File Server Print Server

3. What is a Computer Network? A computer network is a linked set of computer systems capable of sharing computer power and resources such as printers, large disk drives, and other databases. There are two types of network:  Local Area Network (LAN)  Wide Area Network (WAN)

7. Protocols A protocol is a standard set of rules used to ensure the proper transfer of data between devices. In network design it is vital that a recognised protocol is used.

8. Local Area Networks A local area network is a computer network across one building or site. Fileserver Printer Work Station Network Cable

9. Peer to Peer Network This describes a very simple network structure where shared resources such as printers are available but where there are very few other facilities. All computers on the network have similar specification and status.

10. Client-Server Network This method of network organisation requires one or more servers to which a number of clients may obtain services. The servers act as central resource managers for the network. (A star topology is often used for this form of network)

11. Network Topologies The network topology is the theoretical arrangement of components on a network. There are five network topologies which you need to be aware of:  Bus  Star  Ring  Mesh  Tree

12. Bus Topology Each device is connected to a main communications line called a bus.

14. Bus Networks A bus network consists of a single medium to which all the host computers are connected. Packets are broadcasted on the medium to all nodes on the network. Network Interface Units Host Computers Terminator Bi-directional medium

15. Bus Topology Recap We can make a cheap network by connecting not just two but a number of hosts to a single link. Such a network is said to have a bus topology. It is also called a multi-drop link.

16. Star Topology In the star topology all stations are connected to a central node, called a hub.

17. Star Networks A star network consists of a special central node (or hub node) to which host computers or terminals are connected. Any host computer can connect to any other host computer via the hub. Special Central Node

19. Star Topology If all the hosts are connected to a central hub (which can be a switching device or a central server also acting as a router) then we have a star topology.

20. Good and Bad Points Hosts communicate by sending their messages to the hub. It then forwards the messages to the destination host.  Star topologies are popular with financial institutions who keep their latest records on a central server. Any changes to the records are updated centrally. 4 It’s easy to control and monitor access to a central server. 6 Cabling costs can still be high if network is spread out. 6 The central hub may cause a bottleneck in busy networks.

21. Star Networks The hub switches messages through to the appropriate destination. The hub may also provide a translation service for devices with different protocols. Star Networks are vulnerable, however. If the hub fails then the network fails. Star Networks may require a lot of cabling and can be expensive to install.

22. Ring Topology Each device is connected to a ring around which signals are sent. The devices are connected to the ring via spurs, or the connection may pass through the interface card

23. Ring Topology A Ring network consists of nodes connected to each other to form a closed loop. Nodes accept data from neighbouring nodes in the form of packets.

25. Ring Topology Operation The Nodes act as repeaters for the packets being forwarded. This means that the Ring can be expanded to any size (although more cable will be required to get the packets to their destinations).

26. Ring Topology - Recap In a Ring Topology hosts are connected to their neighbours to form a loop. 4 Less cabling is required because neighbouring hosts are not usually far apart. 6 A break in one of the links will stop the network from working (but failures can be quickly detected and fixed).

27. Messages are passed from one host to the next until they reach the destination host. Typically messages pass the whole way around the ring and are checked and removed by the hosts That sent them.

28. Mesh Topology A mesh network is the most expensive type of network to install

29. Mesh Topology A mesh topology is a network in which the connections between nodes is random. Mesh topologies include fully connected networks and random networks (e.g. Internet). Redundant connections in random networks ensure that alternative routes exist for data. Fully connected Network with 5 nodes Random Network with 7 nodes

30. Mesh Topology - Recap A randomly connected network is called a mesh topology. Mesh topologies are most suited to networks that are built up over time.  The Internet is a mesh topology. It has been added to over time with no central control. 4 Mesh topologies are easily extended. 4 Often there is more than one possible route for messages to follow. If one path fails then another can be used. 6 There is no simple algorithm for routing messages. Messages are often sent over sub-optimal paths. 6 Control and security can be difficult to enforce effectively.

31. Fully Connected Network At the other extreme, we do not have to share links at all. Each pair of hosts could have their own exclusive link. This would ensure the fastest possible communication between any two hosts. Such a network is called a fully connected network. 6 Of course there is one small drawback to this type of network: the number of links.  The cabling and maintenance  costs are high.

32. Tree Networks A tree network (as used in LANs) is a variant of the Bus topology. Nodes are connected in a tree structure and messages are broadcast across whole tree. Communications Link Root Node Host Computers

33. Tree Networks Tree topologies have the advantage that they are easy to expand. Furthermore, if a fault occurs, the effected branch can be easily isolated so that the rest of the network is not effected. The disadvantage is that signals can be reflected from the ends of branches and cause interference. For this reason, Tree Networks are usually run at lower speeds.

34. Tree Topology - Recap A tree topology has a root and branches that gives it a distinctive tree shape. Messages pass up the tree until they reach a branching point in common with the destination host. They are then passed down the tree to the destination. 4 Tree topology is easily extended. 4 Easy to install and wire. 4 It is relatively easy to detect faults & remove parts. 4 Each device has its own its own connection to the central node, 6 A large number messages pass through the root, which may become a communications bottleneck. 6 Overall the tree topology is more difficult to configure and wire than other topologies.

35. Hardware Client, Server, Hub, Switch, Router, Network Interface Card (NIC) and Repeater. Distributed Network

36. Client-Server Network This method of network organisation requires one or more servers to which a number of clients may obtain services. The servers act as central resource managers for the network. A star topology is often used for this form of network.

37. Network Hardware Network hardware will include:  stations  servers file, print, web  passive components cables, connections, etc  active components repeaters, hubs, switches

38. Network Stations The network station (often called the client) will normally comprise:  PC  Network interface card (NIC). The NIC allows the computer to communicate with the network  Network Operating Systems Eg Windows Server, Mac Server, Linux Server

39. Network Servers A network server is a computer which acts as a central storage point for files and applications. Servers also act as a connection point to shared peripherals such as printers.

40. Active Components Active components are required for all but the simplest of networks. These include:  Hubs  Switches  Repeaters

41. Hubs A hub is a device which allows the interconnection of a group of users. A hub will forward any packet of data it receives over one port from one station to all of the remaining ports. Hubs are used in the star topology.

42. Switches A switch is “smarter” than a hub and offers more bandwidth. A switch forwards data packets only to the appropriate port for the intended recipient. The switch establishes a temporary connection between the source and the destination.

43. Repeaters Due to loss of signal strength it is often necessary to use a repeater to boost the signal. A repeater is a hardware device to link together two cable segments. The repeater amplifies the signal it receives before passing it on.

44. Routers A router receives packets of data transmitted over a network, and using their IP address*, forwards them to the correct destinations over the most efficient available path.

45. IP Address Every computer on the network must have an IP address. Think of it as a Postcode, for each machine This IP address must be unique. It is set by Network Server software.

46. Routers A router is a device which receives data packets and sends them on via an appropriate route. It will have a number of network interface ports to allow connection to different segments to which data packets may be directed.

47. Network Software Network Auditing and Monitoring Software  This software keeps a track of network activity.  It records user activity and workstation activity.  In a commercial organisation this sort of auditing and monitoring can be used to detect fraud and suspicious activity.

48. Software Software - Network Operating Systems exist on all client machines allowing them to connect to the network. On a server, network management software is found allowing the network administrator to configure, find faults and monitor performance of the network. Other server software allows for monitoring of the network and its users and auditing, such as tracking how many computers are connected to the network and how many machines run a particular version of a piece of software. Server software allows administrators to configure network user accounts, setting disc quotas, access rights (read, write, create, delete, execute, modify).

49. Arrangements Can you do the following… Description, exemplification and application of network strategy:  - identification and description of network topologies, including LANs, WANs, distributed networks  - identification and description of hardware, client/server, network adapter, structured cabling  - identification and description of software, including network operating system, network accounts  - description of audit and monitoring procedures and software

50. Questions 1.What is a distributed database? (2) A monthly report is produced by several employees creating and editing sections of the document and then sending these to an editor over a Local Area Network. 2. Name a suitable topology for this Local Area Network and draw a diagram of this topology.(2) 3. Explain why an organisation needs a network strategy and state the five areas it needs to address. 4. What is structured cabling? Name two types.

51. Additional Questions 1. Explain the difference between a Local Area Network and a Wide Area Network. (2) 2. What does a distributed network mean? (1) 3. Explain the difference between a client server network and a peer-to-peer network. (2) 4. What functions does a network adapter card give to a computer on a LAN? (2) 5. What advantage does a fibre-optic cable give over a twisted pair or co-axial cable? (1) 6. What additional piece of hardware is required in an Ethernet network when longish distances need be covered? (1) 7. Explain why a file server and a network computer both require a network operating system, and explain the main difference between the two versions.(2) 8. What is the main function of network auditing and monitoring software? (2)