- 1. NETWORKTOPOLOGIESNETWORKTOPOLOGIES Prf.Madhuri Nitin Badgujar (M.Sc.IT,MCA) Birla College of Arts, Commerce and science, Kalyan(w)
2. NETWORKTOPOLOGIESNETWORKTOPOLOGIES There are three basic configurations used to connect computers they are the Bus Ring Star 3. Bus topologyBus topology This type of network was widely used in the 1980s 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 4. How a Bus Peer to PeerHow a Bus Peer to Peer Network WorksNetwork 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 5. How it workedHow it worked The type of wires used for Bus Networks in the 80s were called Thicknet and Thinnet A Thicknet cable (very large about 1 inch in diameter usually yellow was hung around a room) Thinnet cables were connected to the PCs NIC and a Transceiver. The Transceiver was tapped into the Thicknet cable To stop the message from bouncing back and forward down the wire (known as signal bounce) both ends of the network are terminated with 50 resistors 6. ProblemsProblems One of the main problems with this type of network is that it is not very fault tolerant, a break or defect in the bus would affect the whole network 7. Advantages It is easy to set up, handle, and implement. It is best-suited for small networks. It costs very less. 8. Disadvantages The cable length is limited. This limits the number of network nodes that can be connected. This network topology can perform well only for a limited number of nodes. When the number of devices connected to the bus increases, the efficiency decreases. It is suitable for networks with low traffic. High traffic increases load on the bus, and the network efficiency drops. It is heavily dependent on the central bus. A fault in the bus leads to network failure. It is not easy to isolate faults in the network nodes. Each device on the network "sees" all the data being transmitted, thus posing a security risk. 9. Ring TopologyRing Topology In Ring topology each node is connected to the two nearest nodes so the entire network forms a circle Data only travels in one direction on a Ring network 10. How this Topology worksHow this Topology works a node has information to send to another computer on the network so it sends the information out on the network to the PC it is connected to, if the information is for this PC (the recipients NIC address is attached to the message, which is like putting an address on an envelope) then the PC accepts the data otherwise it passes the information on to the next PC by repeating the data back out on the line This method of repeating the data helps keep the integrity of the data readable by other computers 11. How it WorksHow it Works As it is better to have computers take turns using the connecting Data cable, Ring topologies incorporated a system called Token passing In this topology, to transmit on the wire your computer must have control of the token or wait for the token to be free Larger Token Ring networks use multiple tokens 12. Problems and SolutionsProblems and Solutions The drawback to this type of topology is that a single malfunctioning workstation can disable the whole network To make sure all the information is sent the receiving PC sends the token back to the sending PC after it has received all the data If the sending PC is finished sending it passes the token to the next PC This type of network was also widely used in the 1980s This type of network used Thinnet cable joining nodes. In the mid 1980s Thinnet cable was replaced by Category 3 Ethernet cable capable of handling up to 10Mbps 13. Advantages The data being transmitted between two nodes passes through all the intermediate nodes. A central server is not required for the management of this topology. The traffic is unidirectional and the data transmission is high- speed. In comparison to a bus, a ring is better at handling load. The adding or removing of network nodes is easy, as the process requires changing only two connections. The configuration makes it easy to identify faults in network nodes. In this topology, each node has the opportunity to transmit data. Thus, it is a very organized network topology. It is less costly than a star topology. 14. Disadvantages The failure of a single node in the network can cause the entire network to fail. The movement or changes made to network nodes affect the entire network's performance. Data sent from one node to another has to pass through all the intermediate nodes. This makes the transmission slower in comparison to that in a star topology. The transmission speed drops with an increase in the number of nodes. There is heavy dependency on the wire connecting the network nodes in the ring. 15. Star topologyStar topology In a Star topology every node is connected through a central device such as a Hub, Switch or Router Compared to a Ring or Bus topology a Star topology requires that more thought be put into its setup HUB 16. The Good and Bad of aThe Good and Bad of a Star NetworkStar Network The upside of a star network is that if any one cable fails then only the node connected on that cable would be affected Another positive point to this type of network is that it is very simple to join two star networks together by connecting their central devices to each other 17. The Good and Bad of aThe Good and Bad of a Star NetworkStar Network As each computer is connected to a central device (Hub) the location of the Hub must be made as central as possible, so as to reduce cable lengths The drawback to this type of topology is if a central device was to fail then all computers connected to that device would not be able to see the network 18. What is a Hub?What is a 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 19. What is a Hub?What is a Hub? Ethernet hubs are by far the most common type, but hubs for other types of networks such as USB also exist 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 20. What is a Hub?What is a Hub? 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 21. Key Features of HubsKey Features of Hubs Hubs classify as Layer 1 devices in the OSI model OSI stands for : The Open Systems Interconnection Basic Reference Model At the physical layer, hubs can support little in the way of sophisticated networking Hubs do not read any of the data passing through them and are not aware of their source or destination 22. Key Features of HubsKey Features of Hubs 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! a packet is a formatted block of data carried by a computer network 23. Different Types of HubsDifferent Types of Hubs Technically speaking, three different types of hubs exist PassivePassive ActiveActive IntelligentIntelligent 24. Passive hubsPassive hubs Passive hubs do not amplify the electrical signal of incoming packets before broadcasting them out to the network Active hubsActive hubs amplify the electrical signal of incoming packets back to their original level before broadcasting them back out on the network 25. Intelligent hubsIntelligent hubs add extra features to an active hub that are of particular importance to businesses An intelligent hub is typically stackable (built in such a way that multiple units can be placed one on top of the other to conserve space). 26. Intelligent hubsIntelligent hubs It also typically includes remote management capabilities via SNMP and virtual LAN (VLAN) support (You can configure or check it from a computer that is connected to it). SNMP-Simple Network Management Protocol 27. Advantages Due to its centralized nature, the topology offers simplicity of operation. It also achieves isolation of each device in the network. Adding or removing network nodes is easy, and can be done without affecting the entire network. Due to the centralized nature, it is easy to detect faults in the network devices. As the analysis of traffic is easy, the topology poses lesser security risk. Data packets do not have to pass through many nodes, like in the case of a ring network. Thus, with the use of a high-capacity central hub, traffic load can be handled at fairly decent speeds. 28. Disadvantages Network operation depends on the functioning of the central hub. Hence, central hub failure leads to failure of the entire network. Also, the number of nodes that can be added, depends on the capacity of the central hub. The setup cost is quite high. 29. What is a Network Switch?What is a Network Switch? A network switch is 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 30. Network SwitchNetwork Switch Network switches appear nearly identical to network hubs, but a switch generally contains more "intelligence" (and a slightly higher price tag) than a hub Unlike hubs, network switches are capable of inspecting data packets as they are received, determining the source and destination device of that packet, and forwarding it appropriately 31. Network SwitchNetwork Switch By delivering each message only to the connected device it was intended for, a network switch conserves network bandwidth and offers generally better performance than a hub 32. Mesh topologyMesh topology A mesh network is a network topology in which each node (called a mesh node) relays data for the network. All nodes cooperate in the distribution of data in the network. Mesh topologies involve the concept of routes. Unlike each of the previous topologies, messages sent on a mesh network can take any of several possible paths from source to destination. Some WANs , most notably the Internet, employ mesh routing. A mesh network in which every device connects to every other is called a full mesh. As shown in the illustration below, partial mesh networks also exist in which some devices connect only indirectly to others. Mesh technology comes into two flavors: Full Mesh: All hosts have a point-to-point connection to every other host in the network. Thus for every new host n(n-1)/2 cables (connection) are required. It provides the most reliable network structure among all network topologies. Partially Mesh: Not all hosts have point-to-point connection to every other host. Hosts connect to each other in some arbitrarily fashion. This topology exists where we need to provide reliability to some host whereas others are not as such necessary. 33. Advantages The arrangement of the network nodes is such that it is possible to transmit data from one node to many other nodes at the same time. The failure of a single node does not cause the entire network to fail as there are alternate paths for data transmission. It can handle heavy traffic, as there are dedicated paths between any two network nodes. Point-to-point contact between every pair of nodes, makes it easy to identify faults. 34. Disadvantages The arrangement wherein every network node is connected to every other node of the network, many connections serve no major purpose. This leads to redundancy of many network connections. A lot of cabling is required. Thus, the costs incurred in setup and maintenance are high. Owing to its complexity, the administration of a mesh network is difficult. 35. What is a Router?What is a Router? Routers are physical devices that join multiple wired or wireless networks together Technically, a wired or wireless router is a Layer 3 gateway, meaning that the wired/wireless router connects networks together A Gateway is a device that acts like a security guard and only allows data in or out if it has the right network headers 36. RoutersRouters Home networkers often use an Internet Protocol (IP) wired or wireless router IP is the most common OSI network layer protocol Protocols are the rules governing the transfer of data information, it can also be compared to how humans use languages (to get your point across you must talk in the same language as the person you are speaking to). 37. RoutersRouters An IP router such as a DSL or cable modem are broadband routers and joins the home's local area network (LAN) to the wide-area network (WAN) of the Internet A Broadband Router is a device that allows multiple PCs to access the Internet using only one address.