Presentation Title Subtitle Introduction to IP and Routing

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 Copyright © 2002 OPNET Technologies, Inc. <Class_Title> - 2

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 Do. D) 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 § Copyright © 2002 OPNET Technologies, Inc. <Class_Title> - 3

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 Copyright © 2002 OPNET Technologies, Inc. <Class_Title> - 4

OSI and TCP/IP stacks Copyright © 2002 OPNET Technologies, Inc. <Class_Title> - 5

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) Copyright © 2002 OPNET Technologies, Inc. <Class_Title> - 6

Dotted Decimal Notation of IP Copyright © 2002 OPNET Technologies, Inc. <Class_Title> - 7

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 Copyright © 2002 OPNET Technologies, Inc. <Class_Title> - 8

IP Addresses : subnet + host address Copyright © 2002 OPNET Technologies, Inc. <Class_Title>

IP Datagram format Copyright © 2002 OPNET Technologies, Inc. <Class_Title> - 10

IP address and Routing (example IP datagram arrives at the middle router) Copyright ©

Routing with IP address Copyright © 2002 OPNET Technologies, Inc. <Class_Title> - 12

Reserved IP addresses Copyright © 2002 OPNET Technologies, Inc. <Class_Title> - 13

IP address written in CIDR notation Copyright © 2002 OPNET Technologies, Inc. <Class_Title> -

IP Addresses Classes • Address classes • Class A: 1. 0. 0. 0 to 127. 255 § 126 networks with 16 million hosts each • Class B: 128. 0. 0. 0 to 191. 255 § 16, 382 networks with 64 K hosts each • Class C: 192. 0. 0. 0 to 223. 255 § 2 million networks with 254 hosts each • Class D: (multicast) 224. 0. 0. 0 to 239. 255 • Class E: 240. 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 § Copyright © 2002 OPNET Technologies, Inc. <Class_Title> - 15

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 Copyright © 2002 OPNET Technologies, Inc. <Class_Title> - 16

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 Copyright © 2002 OPNET Technologies, Inc. <Class_Title> - 17

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 Copyright © 2002 OPNET Technologies, Inc. <Class_Title> - 18

IP Quality of Service (Qo. S) • 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 Copyright © 2002 OPNET Technologies, Inc. <Class_Title> - 19

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 Copyright © 2002 OPNET Technologies, Inc. <Class_Title> - 20

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 Copyright © 2002 OPNET Technologies, Inc. <Class_Title> - 21