6. Network Model

1. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model 6. Network Model

2. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model Why Network Protocol Models? • Network communication is an extremely complex task • Need cooperative efforts from all nodes involved • A standard model helps to describe the task of a networking product or service • Also help in troubleshooting by providing a frame of reference

3. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model 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)

4. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model The OSI 7-layer Model • OSI - Open Systems Interconnection • Defined in 1984 and become an international standard All Away People Pizza Seem Sausage To Throw Need Not Data Do Processing Please

5. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model 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

6. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model Relationship of OSI layers Virtual Communication Physical Communication

7. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model 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

8. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model • To identify the language (protocol) of each layer, identifier (header and trailer) are added to data

9. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model 1. Physical Layer Example protocols: Ethernet, Token Ring (Physical part) Appl. Appl. • 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 Pres. Pres. Sess. Sess. Tran. Tran. Netw. Netw. Data. Data. Phys. Phys.

10. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model 2. Data Link Layer Example protocols: Ethernet, Token Ring Appl. Appl. • Make data frames • Provide error-free frame transfer by acknowledgment and retransmission Pres. Pres. Sess. Sess. Tran. Tran. Frame Netw. Netw. Data. Data. Phys. Phys.

11. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model

12. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model 3. Network Layer Example protocols: IP, IPX • 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 Appl. Appl. Pres. Pres. Sess. Sess. Tran. Tran. Netw. Netw. Data. Data. Phys. Phys.

13. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model

14. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model Receiving Sending 1 3 2 1 2 3 4. Transport Layer Example protocols: TCP, SPX, NWLink • Ensure packets are delivered error free, insequence • Translate between packets and message Appl. Appl. Pres. Pres. Sess. Sess. Tran. Tran. Netw. Netw. Data. Data. Phys. Phys.

15. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model 5. Session Layer Example application program: Winsock, UNIX Socket Appl. Appl. • Establishment, maintaining and release of session • Provide dialog management • Regulate which side transmit, when, for how long (Sync.) • Provide synchronization between user tasks Pres. Pres. Sess. Sess. Tran. Tran. Netw. Netw. Data. Data. Phys. Phys.

16. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model What is a Session? A. Consecutive sessions on a transport layer connection B. Consecutive sessions on a multiple transport layer connections 1 2 3 1 2 3 C. Both 1 2 3

17. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model 6. Presentation Layer Example application program: redirector (NT), SSL Appl. Appl. • 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 Pres. Pres. Sess. Sess. Tran. Tran. Netw. Netw. Data. Data. Phys. Phys.

18. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model 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. Appl. Pres. Pres. Sess. Sess. Tran. Tran. Netw. Netw. Data. Data. Phys. Phys.

19. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model PictureTel Example: File Transfer • The most traditional network task • Implemented by a simple Application Layer protocol called FTP FTP Client FTP Server Network

20. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model Utility: WS_FTP

21. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model PictureTel WS_FTP FTP FTP FTP Client FTP Server Layers 5-7 Layers 5-7 Layer 4 TCP TCP Layer 4 Layer 3 IP IP Layer 3 Ethernet Ethernet Layers 1,2 Layers 1,2

22. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model The 802 Project Model • IEEE launched the Project 802 in 1980 February • Predate the ISO standard, but the development was performed in roughly the same time • Objective: To clearly define the network standards for different kind of physical components of a network - the interface card and the cabling • Enhance the Data Link and Physical layers of the OSI model

23. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model IEEE 802 Categories 802.1 Internetworking 802.2 Logical Link Control (LLC) 802.3 Carrier-Sense Multiple Access with Collision Detection (CSMA/CD) LAN (Ethernet) 802.4 Token Bus LAN 802.5 Token Ring LAN 802.6 Metropolitan Area Network (MAN) 802.7 Broadband Technical Advisory Group 802.8 Fiber-Optic Technical Advisory Group 802.9 Integrated Voice/Data Networks 802.10 Network Security 802.11 Wireless Networks 802.12 Demand Priority Access LAN, 100 BaseVG-AnyLAN

24. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model Enhancements to the OSI Model • Divide the Data Link layer into 2 sub-layers • Logical Link Control Sub-layer • Define the use of service access points (SAPs) as an interface for higher layer to Data Link layer • Media Access Control Sub-layer • Directly interface with the network card • For delivering error-free data communications

25. ENG224 INFORMATION TECHNOLOGY – Part I 6. Network Model 802.1 Logical Link Control (LLC) 802.2 Media Access Control (MAC) 802.3 802.4 802.5 802.12