Presentation Title Subtitle Author Copyright © 2002 OPNET Technologies, Inc. TM Introduction to IP and Routing

Copyright © 2002 OPNET Technologies, Inc. - 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

Copyright © 2002 OPNET Technologies, Inc. - 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

Copyright © 2002 OPNET Technologies, Inc. - 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

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

Copyright © 2002 OPNET Technologies, Inc. - 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:   Each machine on a network has a unique IP Address Numbers assigned by the Network Information Center (NIC)

Copyright © 2002 OPNET Technologies, Inc. - 7 IP Addresses Classes Address classes Class A: to  126 networks with 16 million hosts each Class B: to  16,382 networks with 64K hosts each Class C: to  2 million networks with 254 hosts each Class D: (multicast) to Class E: 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. - 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

Copyright © 2002 OPNET Technologies, Inc. - 9 Dynamic Host Configuration Protocol 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 Host names Familiar names are easier to remember than IP Addresses Names can be registered (internic).net,.com,.gov,.au,.fr, etc e.g. “Ping” a host name to get its IP Address

Copyright © 2002 OPNET Technologies, Inc 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 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

Copyright © 2002 OPNET Technologies, Inc 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 IPv6

Copyright © 2002 OPNET Technologies, Inc 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 Static Routing Manually assign routes to destinations Flooding

Copyright © 2002 OPNET Technologies, Inc Dynamic Routing DistanceVector Each router maintains a table giving  Best known distance to each destination  Which line/interface to use Tables updated by exchanging with neighbors  Bellman-Ford is most well-known algorithm  Was the original ARPANET routing algorithm  Used by RIP on the internet

Copyright © 2002 OPNET Technologies, Inc Dynamic Routing, cont. Link State routing Discovers neighbors and addresses Measures cost to neighbor  Delay  Queue size  Bandwidth  Etc Creates a packet with all of this info Sends packet to all other routers Computes shortest path to every other router Table can become quite large

Copyright © 2002 OPNET Technologies, Inc Hierarchical Routing Not every possible destination needs to be known by every router Routers within a subnet May only need to know internal destinations Needs to also know “border” routers to get to the outside

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