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This PPt explains about router and routing

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  1. 1. Concepts of Router and Routing 1
  2. 2. Router• A device that connects two or more computer networks together is called as a Router• It allows two or more different computer networks to send data to each other 2
  3. 3. Router Contd….Fig.1 3
  4. 4. Router Contd….Fig.2 4
  5. 5. Router Contd….Fig.3 5
  6. 6. Router Contd….• A router is a computer whose software and hardware are designed to perform the tasks of routing and forwarding information (sending the information to the destination). 6
  7. 7. Router Contd….Routers generally contain • A specialized operating system • RAM • NVRAM • Flash memory and • one or more processors 7
  8. 8. Router Contd….• Routers operate in two different planes• Control Plane: The router learns the outgoing interface that is most appropriate for forwarding specific packets to specific destinations• Forwarding Plane: The router is responsible for the actual process of sending a packet received on a logical interface to an outbound logical interface 8
  9. 9. Control Plane Activities• Routers periodically disseminate topology information to all the other routers with the help of control packets (e.g. :HELLO, TC packets)• Topology information contains the information about the one hop and two hop neighbors to each of the router, link cost etc• Link cost can be defined in several terms: a time estimate, a distance estimate, congestion estimate, bandwidth estimate etc. for the communication link between router and its one hop neighbor• After learning the topology information, every router computes shortest route from itself to every other router in the Internet• The computed shortest routes are stored in a route cache in the form of routing table• Routing table gives the nest hop router to which packet has to be forwarded to send it in the shortest path for each destination IP address ( network part of IP address) 9
  10. 10. Forward Plane Activities• The Packet which arrive at Router’s interface is first buffered (stored)• The Router examines the packet’s header and the picks the destination IP address to where the packet has to reach• It looks into the routing table to know the next hop router to which the packet has to be forwarded in order to send it in the shortest path• Then Router forwards the packet to the corresponding next Router address via one of its ports• The same process is carried out at each Router along the shortest path till the destination router is reached 10
  11. 11. Types of RoutersVarious types of routers • Edge Router • Border Router • Core router • Enterprise Router • Access Router • Distribution Router 11
  12. 12. Symbol for RouterFig.4 12
  13. 13. 13 Router Connecting Various Subnets TOKEN RI NG Fig.5 NETWORK A BUS N Y Z ROUTERETHERNE X TNETWORK C
  14. 14. Router Concepts• Router must have three interfaces and three Network Interface Cards (NICs) to interact with the networks A, B and C at the junctions X and Y and Z as shown in figure 5• In Internet, there are number of networks that communicate with each other. Therefore, there would be as many routers as networks 14
  15. 15. Routing• Routing is the process of selecting paths in a network to send data or physical traffic• Routing is performed for many kinds of networks, including the telephone network , the Internet, and transport networks 15
  16. 16. Router Contd….• Routing directs forwarding, the passing of logically addressed packets from their source towards their ultimate destination through intermediary nodes• Nodes are hardware devices called routers, bridges, gateways, firewalls, or switches 16
  17. 17. Router Contd….• Ordinary computers with multiple network cards can also forward packets and perform routing, though they are not specialized hardware and may suffer from limited performance• The routing process usually directs forwarding on the basis of routing tables which maintain a record of the routes to various network destinations• Thus constructing routing tables, which are held in the routers memory, becomes very important for efficient routing 17
  18. 18. Router Contd….• Therefore, Routing is the process of sending the data in the form of packets called datagrams from the source to the destination computers through many networks• Routing algorithms take the decisions about routing process and factors affecting them are as follows• Least cost routing• Distributed routing• Packet life time 18
  20. 20. SummaryIn this class, you have learnt about • Router and routing concepts 20
  21. 21. Quiz1. A Router is connected to five networks. Then number of NICs required by the router is a) 2 b) 3 c) 5 d) 7 21
  22. 22. Frequently Asked Questions1. Differentiate between Router and Routing?2. List the various types of routers3. Write short notes on routing 22