The OSI Model & Protocols

1. The OSI Model & Protocols Monday, December 1, 2014

2. The OSI Model • Open Systems Interconnection (OSI). • Specifies how computer networking devices communicate with each other.

3. The OSI Model – Standards • Networks are made up of components manufactured by many companies. • In order for the network to function properly, these components must be able to communicate with each other. • Most manufacturers follow industry standards so that their products will work with those from other companies.

4. The ISO • International Standardization Organization. • Develops product standards for the computer industry. • Coordinates the activities of other standards organizations. • ISO’s main objective is to allow networks to work efficiently. • The ISO developed the OSI Model.

5. The OSI Model • A set of guidelines for the entire communication process. • Also specifies how applications and devices should work in order to communicate with each other.

6. Layers • Seven layers in the OSI model. • Each is responsible for one particular aspect of the communication process. • One layer for how information is addressed from one computer to another. • Another layer for error checking.

7. Ensuring Compatibility • Before OSI, no standardization existed for the exchange of information on a network. • Devices were developed with no thought to how they’d work with other products. • By following the OSI model, companies ensure their products can be used on a network with other companies’ products.

8. The Seven OSI Model Layers • Application • Presentation • Session • Transport • Network • Data Link • Physical

9. Application Layer • Handles the exchange of information between the programs running on a computer and other network services • Example: a database or print server

10. Presentation Layer • Formats information so that a software application can read the information.

11. Session Layer • Handles how two devices communicate. • Handles how two computers on the network communicate.

12. Transport Layer • Corrects transmission errors. • Ensures that information is delivered reliably.

13. Network Layer • Identifies computers on a network. • Determines how to direct information transferring over a network.

14. Data Link Layer • Groups data into sets to prepare the data for transfer over the network. • “Packets”

15. Physical Layer • Defines how a transmission medium (cable, etc.) attaches to the computer. • Also specifies how electrical information transfers on the transmission medium.

16. Protocols • Before two computers can transfer information over a network, they must communicate. • Protocols are the rules that allow them to do that.

17. Protocols • Hardware or software components that carry out the OSI model guidelines for transferring information over the network. • May be one component or a collection of components that carry out a task.

18. Protocol Stacks • Also known as a protocol suite. • Made up of multiple protocols used to exchange information. • One might specify how NIC’s might communicate. • Another might specify how computers read information from the NIC.

19. Layers • A section of a protocol stack that’s responsible for one aspect of information transfer. • Some are capable of performing more than one function, so these layers do not necessarily correspond to the OSI Model layers.

20. Compatibility • All computers on a network have to have the same protocols in order to communicate. • A layer on the protocol stack on one computer has to be able to communicate with the same layer on the protocol stack on another.

21. Standards • A network device designed to use an accepted protocol can communicate effectively with any other device using the same protocol. • The OSI Model & Protocol standards ensure this compatibility.

22. IPX/SPX Protocols • Combine to make the protocol suite that is used to transfer information on networks powered by Netware

23. IPX • Internetwork Packet Exchange (IPX) • Derived from a protocol developed by Xerox Corporation. • Used to transfer information between devices located on different networks and keep track of the locations of network devices in relation to other devices. • When IPX transfers data, it does not monitor the transmission or check the reliability of the data.

24. SPX • Sequenced Packet Exchange (SPX) • An extension of the IPX protocol. • Transfers information, but unlike IPX, SPX makes a connection between two network devices and monitors the transmission. • It also ensures that the data has no errors.

25. IPX/SPX – Popular • Because of the popularity of Novell Netware, many manufacturers make their products support the IPX/SPX protocols.

26. IPX/SPX – Tunneling • Describes the process of using a protocol to transfer data through a different kind of network. • IPX/SPX protocols support IP tunneling, so information can be transferred between NetWare networks using a TCP/IP network or the Internet. • The information and IPX/SPX protocols are bundled within the TCP/IP protocol suite. • When it reaches its destination, the TCP/IP protocols are removed.

27. A Little Background on TCP/IP • TCP/IP is designed to transfer bundled information (packets) without any concern for what’s in the packet. • TCP/IP doesn’t care what’s in the packet and doesn’t care what operating system is in use. • So, you can bundle the IPX/SPX and send it through TCP/IP without the IP affecting the data. • TCP/IP ignores the contents of the packet just as a postal delivery ignores the contents of a letter she delivers.

28. IPX/SPX – Ports • A location in memory used by a program. • Ports are virtual locations and exist only when the computer is running. • The IPX/SPX protocols use ports to indicate where information must be delivered in order to reach the appropriate program.

29. NetBEUI Protocol • NetBIOS Extended User Interface. • A network protocol used in small Microsoft-based networks. • For example, a network of computers running Windows 95 or 98.

30. NetBIOS • Network Basic Input/Output System • Developed by IBM as a way of allowing computers to communicate with each other on a network. • NetBEUI protocol developed to improve upon NetBIOS to make it more efficient.

31. NetBEUI - Performance • Small and efficient, the NetBEUI protocol does not require a lot of computer resources, such as memory or processing power. • It can transfer information on a network much faster than other protocols. • However, it’s not used on wide area networks.

32. NetBEUI – Microsoft • Found almost exclusively in networks based on products by Microsoft. • All Microsoft products that connect to a network use the NetBEUI protocol.

33. NetBEUI – Configuration • Quite simple to set up. • When configuring a network computer using NetBEUI protocol, the administrator must give the computer a unique name to identify it on the network. • The administrator also has to assign the computer to a workgroup, which will allow the computer to access a predetermined set of network resources.

34. NetBEUI – Non-routable Protocol • The major disadvantage in using the NetBEUI protocol is that it cannot be used on a large network. • Many large networks use routers (we’ve talked about routers already) to link parts of the network. • Unfortunately, NetBEUI is a non-routable protocol, which means that it cannot pass through network routers.

35. TCP/IP Protocols • A collection, or stack, of protocols used to allow communication between networks with different types of computer systems. • TCP/IP is the set of protocols used on the Internet.

36. TCP/IP – Development • Originally developed in the late 1960’s in response to the needs of the U. S. Department of Defense. • Developed by Vinton Cert and Robert Kahn. • Has been available for many years. • Repeatedly tested and improved. • Most of the ones used today to connect computers are the ones developed 30 years ago.

37. TCP/IP – Popularity • Quickly became popular because the companies that supplied the D.O.D. had to make their products support TCP/IP. • As a result, TCP/IP is very popular and many companies use it to transfer information. • The widespread growth of the Internet is also a factor in the popularity of TCP/IP. • The fact that it works and works well played a role, too, I’m sure.

38. TCP/IP – Reroute • Designed to make sure a collection of networked computers would withstand a major disruption, such as war, that could damage several parts of the network. • One of the main benefits of TCP/IP is that it can be used to quickly reroute information around damaged parts of a network.

39. TCP/IP – Network Types • Used on different types of networks, including Ethernet, Token Ring, even networks using modern connections. • Almost all networks support TCP/IP.

40. TCP/IP – Open Standard • A major benefit of TCP/IP – it’s open standard. • That means that any company or person can design a device or software program that uses TCP/IP without having to pay a royalty or licensing fee.

41. Common TCP/IP Protocols • Many protocols make up TCP/IP.

42. TCP • Transmission Control Protocol • Used to transfer information between two devices on a TCP/IP network. • Uses virtual ports to make connections. • Monitors the transmission of information.

43. IP • Internet Protocol • Responsible for the addressing information. • Used to direct information to its proper destination on a TCP/IP network.

44. FTP • File Transfer Protocol • One of the most widely recognized and used TCP/IP protocols. • Used to transfer documents between different types of computers on a TCP/IP network. • That’s documents (whole files) as opposed to other information packets.

45. HTTP • HyperText Transfer Protocol • Another of the most widely used protocols used on the Internet. • Used to transfer information from Web servers to Web browsers.

46. UDP • User Datagram Protocol • Uses virtual ports to transfer information between two applications on a TCP/IP network. • Slightly faster than TCP but not as reliable.

47. DHCP • Dynamic Host Configuration Protocol • Used to allow communication between network devices and a server that administers IP numbers, called a DHCP server.

48. DNS • Domain Name Server • Used to match Internet computer names to their corresponding IP numbers • Allows users to type a computer name such as www.company.com instead of an IP number such as 192.168.53.3 to access a computer.

49. WINS • Windows Internet Name Service • A protocol used on Microsoft-based TCP/IP networks. • A server running WINS can match Microsoft network computer names to IP numbers. • This allows computers on the Microsoft network to communicate with other networks and computers that use the TCP/IP suite.