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Introduction to IP and Routing Gur Saran Adhar

Introduction to IP and Routing Gur Saran Adhar. What is IP?. Connectionless, unreliable, best-efforts packet delivery system Connectionless Just addresses a packet and sends it (analogous to mailing a letter)

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Introduction to IP and Routing Gur Saran Adhar

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  1. Introduction to IP and RoutingGur Saran Adhar

  2. What is IP? • Connectionless, unreliable, best-efforts packet delivery system • Connectionless • Just addresses a packet and sends it (analogous to mailing a letter) • Does not need to create a connection to the destination. That is the responsibility of a higher layer (like TCP) • Unreliable • Packets may be lost, delayed, duplicated, out of order, or damaged in transmission • Up to higher layer to provide reliability • Best-efforts • Packets will not be discarded arbitrarily, without good cause • Exhaustion of resources • Failure of lower layer

  3. OSI vs. TCP/IP • The TCP/IP protocol stack does not match the OSI protocol stack exactly • TCP/IP in use before OSI protocols appeared • ARPANET (research network sponsored by DoD) needed • Ability to connect multiple networks together • Ability to survive loss of subnet hardware, with no connection loss • Internet layer developed: Can inject packets that travel independently to the destination • One of the first implementation by Berkeley • Good implementation • Free

  4. OSI vs. TCP/IP, cont. • OSI model developed before any implementation • TCP/IP model developed after it was implemented • Some companies already had product with TCP/IP • Did not want to support 2 protocols • OSI more complex than TCP/IP • Q: What do you get when you cross a mobster with an international standard? • A: Someone who makes you an offer you can’t understand • Waited to see how others would use OSI • TCP/IP became more widespread, while nothing really happened with OSI • OSI still used as a first example of a layered protocol stack

  5. OSI and TCP/IP stacks

  6. IP Addresses • IP addresses are analogous to postal addresses • Destination is described from the general to the specific • Zip code/State -> City -> Street -> Building -> Person • Network Address -> Host Address • IP Addresses consist of 4 numbers, separated by periods • Each number ranges from 0 – 255 • Examples: • 12.221.14.2 • 192.15.223.111 • Each machine interface on a network has a unique IP Address • Numbers assigned by the Network Information Center (NIC)

  7. Dotted Decimal Notation of IP

  8. IP Subnets • Subnets are used if you have more machines than IP addresses • Allows a network to be split into several parts for internal use, but still act like a single network to the outside world • IP packets are routed depending on their destination • Other network: forwarded to next router • This network: forwarded to internal destination • Uses “Subnet Mask” to determine internal destination

  9. IP Addresses : subnet + host address

  10. IP Datagram format

  11. IP address and Routing (example IP datagram arrives at the middle router)

  12. Routing with IP address

  13. Reserved IP addresses

  14. IP address written in CIDR notation

  15. IP Addresses Classes • Address classes • Class A: 1.0.0.0 to 127.255.255.255 • 126 networks with 16 million hosts each • Class B: 128.0.0.0 to 191.255.255.255 • 16,382 networks with 64K hosts each • Class C: 192.0.0.0 to 223.255.255.255 • 2 million networks with 254 hosts each • Class D: (multicast) 224.0.0.0 to 239.255.255.255 • Class E: 240.0.0.0 and up: reserved for future use • 127.xx.yy.zz is a “loopback” address • Not actually sent on the wire • Processed locally, as an incoming packet

  16. Dynamic Host Configuration Protocol (DHCP) • Alternative to “static” IP Addresses • Allows for even more hosts within a subnet • Major downfall is that you cannot host a service easily

  17. Host names • Familiar names are easier to remember than IP Addresses • Names can be registered (internic) • .net, .com, .gov, .au, .fr, etc • e.g. www.amazon.com, www.opnet.com • “Ping” a host name to get its IP Address

  18. Domain Name System (DNS) • A DNS server keeps track of the meaning of host and domain names • Even without DNS, you can get to other internet locations, using the IP Address

  19. IP Quality of Service (QoS) • Some applications require different service than others • Considerations: • Connection establishment delay • Connection establishment failure probability • Throughput • Transit delay • Residual error ratio • Protection • Priority • Delay variation

  20. IP Security (IPsec) • Developing standard for security at the network layer • Earlier security approaches have inserted security at the application layer • Useful for implementing • Virtual Private Networks (VPNs) • Remote user access through dial-up connection to private networks • Security arrangements can be handled without requiring changes to individual user computers. • Cisco has been a leader in proposing IPsec as a standard (or combination of standards and technologies) and has included support for it in its routers

  21. IP Routing • Many different routing algorithms • Static • Routes decided in advance • Not adaptive to network changes • Dynamic • Change routing decisions to reflect changes in topology and traffic • Adaptive to network changes

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