Networking and Internetworking Devices

1
Networking and Internetworking Devices

• Repeaters
• Bridges
• Routers
• Gateways
• Routing Algorithms

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Outline

• Routing Algorithms
• Dykstra
• Bellman Ford
• Routing In the Internet
• DNS

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Router and the OSI Model
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Routers in an Internet
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Distance Vector Routing

• Knowledge about the entire network
• Routing only to neighbors
• Information Sharing with neighbors

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Link State Routing

• Knowledge of neighborhood
• Shares with all routers flooding
• Information sharing when change

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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-gtnode
• Breadth Search from root
• Select lowest cost
• Add node and arc

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Bellman-Ford

• Do until a path exists to each node
• Develop paths in increasing depth
• While n lt maxLength or until allNodesFound
• Find all paths of length n
• n

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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.
• Its suitable for small networks
• RIP is used by IPX/SPX and TCP/IP.

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Distance Vector Routing Table
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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.

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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.

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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

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Physical Address Determination

• ARP
• The arp program displays and modifies ip to mac
  address translation
• a -gt display all entries in table
• d -gt delete a host entry
• Login to sheba
• type arp sheba
• type arp a

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tracert

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

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DNS - nslookup

• nslookup www.cbu.edu
• What is displayed?
• CNAME

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What ports

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