Networking Models: Client-Server and Peer-to-Peer

1. Faculty of Science and Humanitarian studies- Al-Aflaj Department of computer Science Network (cont…)

2. Application area of a Network • IP telephony or Voice over IP (VoIP) • email (electronic mail) • Electronic book readers and online digital libraries • e-commerce (electronic commerce) • shopping from home

3. Application area of a Network • Professional organizations, such as the ACM (www.acm.org) and the IEEE Computer Society (www.computer.org), already have all their journals and conference proceedings online

4. Networking models • Much of this information is accessed using the: • Domain model: Client-server model • Workgroup model: Peer-to-peer model

5. Client–server model Domain model The client–server model is a distributed application structure that partitions tasks or workloads between the providers of a resource or service, called servers, and service requesters, called clients. A network with two clients and one server.

6. Client and Server computer role in networking Domain model • Server : • A server device typically stores files and databases including more complex applications like Web sites. • Server devices have a higher-powered central processors, more memory, and larger disk drives than clients. • Client: • Client devices are typically PCs with network software applications installed that request and receive information over the network. • Mobile devices, as well as desktop computers, can both function as clients.

7. Client and server communication Domain model • Communication takes the form of the client process sending a message over the network to the server process. • The client process then waits for a reply message. When the server process gets the request, it performs the requested work or looks up the requested data and sends back a reply. • This exchange of messages is an example of inter-process communication.

8. Peer to peer model Workgroup model • Peer-to-peer (P2P) computing or networking is a distributed application architecture that partitions tasks or workloads between peers • Every person (peer) can, in principle, communicate with one or more other people • There is no fixed division into clients and servers.

9. Peer to peer model Workgroup model • Each computer is in charge of its own security, • The computers are often simply home computers • Everyone participates in the task of distributing content, and there is often no central point of control. • there is no dedicated infrastructure unlike in a CDN • (content delivery network)

10. Example of Peer to peer system Workgroup model • BitTorrent: BitTorrent is a communication protocol for peer-to-peer • file sharing ("P2P") which is used to distribute data and electronic files  • over the Internet.

11. SUMMARY: PROS & CONS Domain model: client- Server

12. SUMMARY: PROS & CONS Workgroupmodel: Peer to Peer

13. Transmission technology The transmission technology can be categorized broadly into two types: • Point-to-point networks. • Broadcast networks

14. Transmission technology Point-to-point links • Point-to-point links connect individual pairs of machines • Point-to-point transmission with exactly one sender and exactly one receiver is sometimes called unicasting.

15. Transmission technology Point-to-point links • To go from the source to the destination a packet on these types of network may have to go through intermediate computers before they reach the desired computer. • Often the packets have to follow multiple routes, of different lengths.

16. Transmission technology Point-to-point links • Hence routing algorithms are very important in the point-to-point networks. • Networks located over wide geographical areas (WAN) use point-to-point transmission.

17. Transmission technology Broadcast links • The communication channel is shared by all the machines on the network • Packets sent by any machine are received by all the others. • Broadcast systems generally use a special code in the address field for addressing a packet to all the concerned computers.

18. Transmission technology Broadcast links • Upon receiving a packet, a machine checks the address field. If the packet is addressed to it then the packet is processed, otherwise the packet is ignored. • Small, localized networks (LAN) tend to use the broadcasting;

19. NETWORK TOPOLOGIES

20. Definition of a Network Topologies • Network topology is the arrangement of the various elements (links, nodes, etc…) of a communication network •  it is the topological structure of a network and may be depicted physically or logically.  • Physical topology is the placement of the various components of a network, including device location and cable installation. • Logical topology illustrates how data flows within a network, distances between nodes, physical interconnections, transmission rates, or signal types.

21. Classification Basic topologies: Bus, Ring, Star

22. Bus network topology • This type of network was widely used in the 1980’s • In this configuration every computer (node) shares the networks total bus capacities. • In this configuration adding more computers will reduce the access speed on the network. • Each computer communicates to other computers on the network independently this is referred to as PEER-TO-PEER networking

23. How it works? • All computers on a network have a distinct address just like your house does • A message would be send from one computer with the address of another computer attached to the message • The message is broadcasted to all the computers on the network until the addressed PC accepts the message

24. How it works? • The type of wires used for Bus Networks in the 80’s were called Thick net and Thin net NIC: network interface controller • Thin net cables were connected to the PC’s NIC and a Transceiver. The Transceiver was tapped into the Thick net cable

25. How it works? • To stop the message from bouncing back and forward down the wire (known as signal bounce) both ends of the network are terminated with 50Ω resistors Resistor Transceiver

26. Advantages and disadvantages of Bus Topology • Management costs can be high •  It is easy to set-up and extend bus network. • Potential for congestion with network traffic • It is not very fault tolerant, a break or defect in the bus would affect the whole network • Relatively inexpensive to implement compared to other networks • Efficiency of Bus network reduces, as the number of devices connected to it increases • Works well for small networks (LAN) • It is not suitable for networks with heavy • traffic

27. Ring Topology • A ring topology is a bus topology in a closed loop • In Ring topology each node is connected to the two nearest nodes so the entire network forms a circle • When one node sends data to another, the data passes through • each intermediate node on the ring until it reaches its destination. • Data only travels in one direction on a Ring network • There is no hierarchical relationship of clients and servers. 

28. How it works? 1.At the start, a free Token is circulating on the ring • 2. machine 1 wants to send some data to machine 4, so it first has to capture the free  Token. It then writes its data and the recipient's address onto the Token 3. The packet of data is then sent to machine 2 who reads the address, realizes it is not its own, so passes it on to machine 3. Machine 3 does the same and passes the Token on to machine 4 4. This time it is the correct address and so number 4 reads the message • 5. It cannot, however, release a free Token on to the ring, it must first send the frame back  to number 1 with an acknowledgement to say that it has received the data

29. How it works? • 6. The receipt is then sent to machine 5 who checks the address, realizes that it is not its own and so  forwards it on to the next machine in the ring, number 7. Machine 6 does the same and forwards the data to number 1, who sent the original message 8. Machine 1 recognizes the address, reads the acknowledgement from number 4, and then releases the free Token back on to the ring ready for the next machine to use

30. Advantages and disadvantges • Easier to manage; easier to locate a defective node or cable problem • Expensive • Requires more cable and network equipment at the start • Well-suited for transmitting signals over long distances on a LAN • Not used as widely as bus topology • Fewer equipment options • Handles high-volume network traffic • Fewer options for expansion to high-speed communication • Enables reliable communication

31. Chain topology Ring topology SW1 SW1 SW2 SW2 SW3 SW3 SW4 SW4

32. Star network • Every node on the network is connected through a central device HUB • A star network consists of one central hub which acts as a conduit to transmit messages

33. Advantages and disadvantges • Good option for modern networks • if a central device was to fail then all computers connected to that device would not be able to see the network • Low startup costs • Easy to manage • Requires more cable than the bus • reduce cable lengths • If one cable fails then only the node connected on that cable would be affected

34. Other Network topology

35. Summary PROS & CONS Disadvantages Advantages Cheap, Easy to Install Difficult to reconfigure Break in bus disablesentire network BUS Cheap, Easy To Install Easy to Reconfigure, faulttolerant More expensivethan bus STAR Efficient, Easy to install Difficult to reconfigure Veryexpensive RING

36. HUB • A hub is usually a small rectangular box, often made of plastic, which receives its power from an ordinary wall outlet • A hub joins multiple computers (or other network devices) together to form a single network segment • On this network segment, all computers can communicate directly with each other

37. HUB • A hub includes a series of ports that each accepts a network cable • Small hubs can network four computers together • They contain four or sometimes five ports • Many times the fifth port is reserved for "uplink" which is the connecting of one hub to another hub or similar device (joining two segments together). • Larger hubs contain eight, 12, 16, and even 24 ports

38. Key Features of Hubs • Hubs classify as Layer 1 devices in the OSI model • Hubs do not read any of the data passing through them and are not aware of their source or destination bridge connects two separate networks as if they are only one network.

39. Role of the HUB • Essentially, a hub simply receives incoming packets, possibly amplifies the electrical signal, and broadcasts these packets out to all devices on the network - including the one that originally sent the packet • Apacket is a formatted block of data carried by a computer network

40. The Hubs can be divided into three types, given as: • Active Hub • Passive Hub • Intelligent Hub

41. Passive HUB Active HUB • Amplifies the incoming signal as well as forward it to multiple devices • Passive Hub works like a simple Bridge. • It does not have the ability to amplify or regenerate any incoming signal. •  Multiport Repeater. •  It receives signal and then forward it to multiple devices

42. Intelligent HUB • It can perform tasks of both Active and Passive buses. • Also, it can perform some other tasks like Bridging and routing. • It increases the speed and effectiveness of total network thus makes the performance of whole network fast and efficient.

43. Switch • A network switchis a small hardware device that joins multiple computers together within one local area network (LAN) • Technically, network switches operate at layer two (Data Link Layer) of the OSI model • When a switch port receives an Ethernet frame from a station, the switch checks the Ethernet addresses to see which port the frame is destined for.

44. Switch • Layer 2 switches can "read" only Layer 2 information, • they can understand the source and destination MAC address of a frame, but are unable to process any Layer 3 (IP header) information. • When a Layer 2 switch receives a frame, it will lookup its MAC address table and forward the frame out the correct port, based on the frame's destination MAC address.

45. SWITCH VERSUS HUB A switch improves performance over a hub in two ways: • First, since there are no collisions, the capacity is used more efficiently. • Second, and more importantly, with a switch multiple frames can be sent simultaneously (by different stations).

46. Routers • The routers will usually connect different kinds of networking technology • Technically, a wired or wireless router is a Layer 3 gateway, meaning that the wired/wireless router connects networks together