ENG 224 INFORMATION TECHNOLOGY Part I 6

ENG 224 INFORMATION TECHNOLOGY – Part I 6. Network Model 1

ENG 224 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 2

ENG 224 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) 3

ENG 224 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 People Seem To Throw Need Data 4 Away Not Do Processing Please Pizza Sausage

ENG 224 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 5 • Shield the upper layer from the details of actual implementation

ENG 224 INFORMATION TECHNOLOGY – Part I 6. Network Model Relationship of OSI layers Virtual Communication Physical Communication 6

ENG 224 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 7

ENG 224 INFORMATION TECHNOLOGY – Part I 6. Network Model • To identify the language (protocol) of each layer, identifier (header and trailer) are added to data 8

ENG 224 INFORMATION TECHNOLOGY – Part I 6. Network Model 1. Physical Layer Example protocols: Ethernet, Token Ring (Physical part) • 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 9 Appl. Pres. Sess. Tran. Netw. Data. Phys.

ENG 224 INFORMATION TECHNOLOGY – Part I 6. Network Model 2. Data Link Layer Example protocols: Ethernet, Token Ring Appl. Pres. Sess. Tran. Netw. Frame Pres. Sess. • Make data frames Appl. Netw. • Provide error-free frame Data. transfer by acknowledgment and Phys. retransmission 10 Data. Phys.

ENG 224 INFORMATION TECHNOLOGY – Part I 6. Network Model 11

ENG 224 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 E 2 15 1 A CA • Determine the route from source to destination computer 12 Appl. Pres. Sess. Tran. Netw. Data. Phys.

ENG 224 INFORMATION TECHNOLOGY – Part I 6. Network Model 13

ENG 224 INFORMATION TECHNOLOGY – Part I 6. Network Model 4. Transport Layer Example protocols: TCP, SPX, NWLink • Ensure packets are delivered Appl. error free, in sequence Appl. • Translate between packets and message Pres. Sess. Receiving Sending Tran. Netw. Data. Phys. 1 14 2 3 3 2

ENG 224 INFORMATION TECHNOLOGY – Part I 6. Network Model 5. Session Layer Example application program: Winsock, UNIX Socket Appl. Pres. Sess. • Regulate which side transmit, Tran. when, for how long (Sync. ) Netw. Tran. • Establishment, maintaining and release of session • Provide dialog management • Provide synchronization between user tasks 15 Netw. Data. Phys.

ENG 224 INFORMATION TECHNOLOGY – Part I 6. Network Model What is a Session? A. Consecutive sessions on a transport layer connection 1 2 3 C. Both 1 16 2 3 B. Consecutive sessions on a multiple transport layer connections 1 2 3

ENG 224 INFORMATION TECHNOLOGY – Part I 6. Network Model 6. Presentation Layer Example application program: redirector (NT), SSL • 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 17 Appl. Pres. Sess. Tran. Netw. Data. Phys.

ENG 224 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 18 Appl. Pres. Sess. Tran. Netw. Data. Phys.

ENG 224 INFORMATION TECHNOLOGY – Part I 6. Network Model Example: File Transfer • The most traditional network task • Implemented by a simple Application Layer protocol called FTP Client FTP Server Picture. Tel Network 19

ENG 224 INFORMATION TECHNOLOGY – Part I 6. Network Model Utility: WS_FTP 20

ENG 224 INFORMATION TECHNOLOGY – Part I 6. Network Model Picture. Tel WS_FTP Client FTP Layers 5 -7 FTP Server Layers 5 -7 Layer 4 TCP Layer 4 Layer 3 IP IP Layer 3 Ethernet Layers 1, 2 21 Layers 1, 2

ENG 224 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 22

ENG 224 INFORMATION TECHNOLOGY – Part I 6. Network Model IEEE 802 Categories 802. 1 802. 3 802. 4 802. 6 Internetworking 802. 2 Logical Link Control (LLC) Carrier-Sense Multiple Access with Collision Detection (CSMA/CD) LAN (Ethernet) Token Bus LAN 802. 5 Token Ring LAN Metropolitan Area Network (MAN) 802. 7 Broadband Technical Advisory Group 802. 8 802. 9 802. 10 802. 12 Fiber-Optic Technical Advisory Group Integrated Voice/Data Networks Network Security 802. 11 Wireless Networks Demand Priority Access LAN, 100 Base. VG-Any. LAN 23

ENG 224 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 24

ENG 224 INFORMATION TECHNOLOGY – Part I 6. Network Model Logical Link 802. 1 Control (LLC) 802. 2 Media Access Control (MAC) 802. 3 802. 5 25 802. 4 802. 12