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

Presentation TitleSubtitle

Author

Copyright © 2002 OPNET Technologies, Inc.

TM

Introduction to IP and Routing

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


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


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


OSI and TCP/IP stacks


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 on a network has a unique IP Address

• Numbers assigned by the Network Information Center (NIC)


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


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


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


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


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


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


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


IPv6


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


Static Routing

• Manually assign routes to destinations

• Flooding


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


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


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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