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Networking and Internetworking Devices

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  1. Networking and Internetworking Devices • Repeaters • Bridges • Routers • Gateways • Routing Algorithms

  2. Outline • Routing Algorithms • Dykstra • Bellman Ford • Routing In the Internet • DNS

  3. Router and the OSI Model

  4. Routers in an Internet

  5. Distance Vector Routing • Knowledge about the entire network • Routing only to neighbors • Information Sharing with neighbors

  6. Link State Routing • Knowledge of neighborhood • Shares with all routers – flooding • Information sharing when change

  7. Dijkstra Algorithm • Find the shortest paths from a given source node to all other nodes by developing paths of increasing path length • Do this until paths to all nodes are found • From ROOT • Do until destination is reached. • Take shortest arc to next node • Add this arc to path • ROOT = this->node • Breadth Search from root • Select lowest cost • Add node and arc

  8. Bellman-Ford • Do until a path exists to each node • Develop paths in increasing depth • While n < maxLength or until allNodesFound • Find all paths of length n • n++

  9. Distance Vector Routing Protocol • RIP (Routing Information Protocol) • Each router uses broadcasting to send its entire information to its neighbors every 30 seconds. • The best path is based on the least number of hops. • It’s suitable for small networks • RIP is used by IPX/SPX and TCP/IP.

  10. Distance Vector Routing Table

  11. Routing Algorithms • Link state routing • If there is a change, each router sends its information about its neighbors to every other router in the network using flooding. • A router, periodically sends a message to its neighbors, the response indicates that the device is alive and functioning. • No response, change has occurred.

  12. Link State Routing Protocol • OSPF (Open Shortest Path First) • More efficient than RIP • Only the changes are sent • each router sends its information about its neighbors to every other router in the network using flooding. • A router, periodically sends a message to its neighbors, the response indicates that the device is alive and functioning. • No response, change has occurred.

  13. Routing in the Internet • Physical Address Determination • Must know physical address to route • arp • Selection of inter-network gateways • tracert • Symbolic and Numeric Addresses • nslookup

  14. Physical Address Determination • ARP • The arp program displays and modifies ip to mac address translation • a -> display all entries in table • d -> delete a host entry Login to sheba type “arp sheba” type “arp –a”

  15. tracert • Login to sheba • Type “tracert www.memphis.com” • This shows the route that a packet takes to communicate with U of Memphis webserver

  16. DNS - nslookup • nslookup www.cbu.edu • What is displayed? • CNAME

  17. What ports • Type “more /etc/services” • This displays the services on sheba and the ports they operate on.