Packet transfer mechanism using routers and IP addresses


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Packet transfer mechanism using routers and IP addresses

  1. 1. Topic : Basics of WAN &WAN ProtocolsSub-Topic : Packet Transfer Mechanism using Router and IP address 1
  2. 2. In the previous classes, you have learnt about• IP Address• Network prefix and host number• Internet address• Sub-netting and no sub-netting• Default gateways
  3. 3. Objectives On completion of this period ,you would be able to know about• Packet transfer mechanism using routers and IP addresses 3
  4. 4. Computer Network ForNet Domain: A domain covered by single monitoring and privacy policies. Forensic Server: Responsible for archiving synopses, query processing & routing, enforcing monitoring, security policies, for the domain.SynApp: equipped routers or hosts. Primaryfunction is to create synopses of networktraffic. May have limited query processing andstorage component as well. Fig .1 4
  5. 5. Recap• Let us remember the functions of a router and also IP address details in the following slides 5
  6. 6. Routers• A router is a hardware component used to interconnect networks Router LAN WAN Fig .2 6
  7. 7. Routers• A router has a network interface card for each network that it is connected to• Networks can use different technologies• Router forwards packets between networks• Router’s job is to transform packets from one network to meet the standards of the second network 7
  8. 8. R Fig .3 8
  9. 9. Internetwork• An internetwork is composed of arbitrarily many networks interconnected by routers Router Fig .4 9EC606A .64 9
  10. 10. InternetworkEthernet Token Ring Router WAN Fig .5 9EC606A .64 10
  11. 11. Routers and IP Addressing• What about routers - connected to two networks ?• Router has multiple IP addresses - one for each interface as shown in the previous slide• IP address depends on network address• IP address specifies an interface, or network attachment point, not a computer 11
  12. 12. TCP/IP Addresses• Addressing in TCP/IP is specified by the Internet Protocol (IP)• Each host is assigned a 32-bit number• This 32-bit number is called the IP address or Internet address 12
  13. 13. TCP/IP Addresses• Each IP address is unique across entire Internet• The format of IP addresses makes routing efficient• Each IP address is divided into a prefix and a suffix • Prefix identifies network to which computer is attached • Suffix identifies computer within that network 13
  14. 14. Packet Transfer Mechanism Using Routers And IP Address• The network layer monitors the delivery of the packet using physical networks• In direct delivery source and destination of packet are located on same physical network• In an indirect delivery, packet moves from router to router until it reaches its final destination 9EC606A .64 14
  15. 15. Packet Transfer Mechanism Using Routers and IP Address• When a packet is placed in its route to its destination it is known as forwarding• It requires a router or a host to have a routing table• There are many forwarding techniques 9EC606A .64 15
  16. 16. Forwarding Techniques• Next hop method• Network / host – specific method• Default method• The path from source to destination is a function of routing protocols 9EC606A .64 16
  17. 17. Examples of Routing Protocols• Routing Information Protocol• Open shortest path first• Intermediate system to Intermediate system 9EC606A .64 17
  18. 18. Examples of Routing Protocols• Packets from one network protocol are wrapped in a packet for another protocol• It is called tunneling done by wrapper network protocol• The routing protocols determine best path for the packet to travel• They maintain routing tables that contain information about networks topology 9EC606A .64 18
  19. 19. Examples of Routing Protocols• In the internet world, IP is used to transport packets through the internet• It uses the information contained in the routing tables with routers• The routing tables may contain several possible routes• The routing algorithm calculates the least-cost path from source to destination 9EC606A .64 19
  20. 20. Examples of Routing Protocols• Routers also maintain routing tables that contain destination address of a node or network• It also has network interface associated with a particular router address• A special type of route is called static route (fixed) that can be entered manually or through software in routing table• The static route cannot be changed dynamically 9EC606A .64 20
  21. 21. Examples of Routing Protocols• Two general routing algorithms are used for computing metric information. i.e. hops, propagation delay, bandwidth, time, channel utilization error rates etc 9EC606A .64 21
  22. 22. Example of Routing Table• Routing Table generated on a Unix system with IP address [Local-Host Routing] Destination Gateway Flags Interface Local host Local host UH le O UGHD le O 7 UGHD le 1 1 Default UG U leO 9EC606A .64 22
  23. 23. Example Routing Table Contd… where• U = route is up & operational• G = packet must pass through at least one router• H = route to a specific host and not a network• D = route was created dynamically 9EC606A .64 23
  24. 24. Example Routing Table Contd….• The table’s first entry illustrated local host-routing• It indicates that any packets meant for local network• It will be forwarded through gateway (IP address of the host). Local host acts as router 9EC606A .64 24
  25. 25. Example Routing Table Contd….• The second entry in the table indicates that the packets are forwarded to another router• The Packets whose destination address is are forwarded to the router ( through interface leO• This router will have the information to where this packet is to be delivered 9EC606A .64 25
  26. 26. Example Routing Table Contd….• The third entry indicates the packets with destination address are to forwarded to gateway• The gateway whose address accessible through le 1 interface 9EC606A .64 26
  27. 27. Example Routing Table Contd….• The Fourth entry entry of table is a default route• When router receives a packet with unknown destination address• The router forwards packet to default router 9EC606A .64 27
  28. 28. Example Routing Table Contd….• If host system receives a packet with destination address• It forwards to router with destination address (since there is no entry in host’s routing table for 28
  29. 29. Example Routing Table Contd….• Routers exchange routing table information with neighbor routers periodically depending upon routing protocol used• They do so in order to update the routing tables as one router may be connected to more than one router 29
  30. 30. SummaryIn this class, you have learnt about • Packet transfer mechanism using routers • And IP addresses with routing options used 30
  31. 31. Quiz1) What is the length of the IP address a) 16-bit b) 32-bit c) 8-bit d) 64-bit 31
  32. 32. Quiz2) A routing table specifies about a) various routes that can be used b) identifies the address c) it’s a table of IP addresses d) none of the above` 32
  33. 33. Frequently Asked Questions1) Explain how packet transfer mechanism is done using routers & IP addresses2) What are the various forwarding techniques used ?3) Discuss with an example importance of a routing table along with its options 33