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2. DATA NETWORKING PROTOCALS

3. Protocol A protocol consists of guidelines for: – How data is formatted into discrete units called packets and frames – How packets and frames are transmitted across one or more networks – How packets and frames are interpreted at the receiving end Protocol is a set of rules

4. 6. Network Model

5. Who define Network Model? Need non-profit making organizations ISO - International Standards Organization e.g. OSI, MPEG-1, 2, 4, etc. (http://www.iso.ch/) IEEE - Institute of Electrical & Electronic Engineers e.g IEEE 802, IEEE 754, etc. (http://www.ieee.org) ITU - International Telecommunication Union e.g. V.34, H.323, H.324, etc. (http://www.itu.int)

6. The OSI 7-layer Model All People Seem ToTo Need Data Processing Away Pizza Sausage Throw Not DoDo Please OSI - Open Systems Interconnection Defined in 1984 and become an international standard

7. Layered Architecture Layering specifies different level of functions and services Each layer works with the layer below and above it Each layer provides services to next layer Shield the upper layer from the details of actual implementation

8. Protocols in a layered architecture Network communication is possible only if machines speaking the same languages (protocols) Since each layer work independently, each layer speaks different languages (protocols) Lead to the concept of a Protocol Stack Network communication is possible only if the Protocol Stacks on two machines are the same

9. To identify the language (protocol) of each layer, identifier (header and trailer) are added to data

10. 1. Physical Layer Define how cable is attached to the Network Adapter Card How many pins in the connector? The impedance? Max/min electrical voltage? Responsible for transmitting bits from one computer to another Example protocols: Ethernet, Token Ring (Physical part) Appl. Pres. Sess. Tran. Netw. Data. Phys. Appl. Pres. Sess. Tran. Netw. Data. Phys.

11. 2. Data Link Layer Make data frames Provide error-free frame transfer by acknowledgment and retransmission Example protocols: Ethernet, Token Ring Frame Appl. Pres. Sess. Tran. Netw. Data. Phys. Appl. Pres. Sess. Tran. Netw. Data. Phys.

13. 3. Network Layer Logical address to physical address translation For TCP/IP running on Ethernet Logical address: IP address 158.132.148.99 Physical address: Ethernet address 00 00 E2 15 1A CA Determine the route from source to destination computer Example protocols: IP, IPX Appl. Pres. Sess. Tran. Netw. Data. Phys. Appl. Pres. Sess. Tran. Netw. Data. Phys.

15. 4. Transport Layer Ensure packets are delivered error free, in sequence Translate between packets and message Example protocols: TCP, SPX, NWLink Appl. Pres. Sess. Tran. Netw. Data. Phys. Appl. Pres. Sess. Tran. Netw. Data. Phys.

16. 5. Session Layer Example application program: Winsock, UNIX Socket Appl. Pres. Sess. Tran. Netw. Data. Phys. Appl. Pres. Sess. Tran. Netw. Data. Phys. Establishment, maintaining and release of session Provide dialog management Regulate which side transmit, when, for how long (Sync.) Provide synchronization between user tasks

17. 6. Presentation Layer Example application program: redirector (NT), SSL Appl. Pres. Sess. Tran. Netw. Data. Phys. Appl. Pres. Sess. Tran. Netw. Data. Phys. Translate data from Application Layer to the format suitable for session layer (the network) Provide data encryption, compression Changing or converting character set, graphic, and file format

18. 7. Application Layer Example protocols: FTP, Telnet, HTTP Entry point for application to access network Directly support user applications E.g. File transfer, email General capabilities: Network access, flow control, Error recovery Appl. Pres. Sess. Tran. Netw. Data. Phys. Appl. Pres. Sess. Tran. Netw. Data. Phys.

19. Example: File Transfer PictureTel FTP ServerFTP Client Network The most traditional network task Implemented by a simple Application Layer protocol called FTP

20. Chapter Summary Protocols are the life blood of a network, thus plan their use carefully. For modern networking TCP/IP Plan to use only the protocols necessary. Plan to use only the protocols necessary.