Computer Networks CSC524 Lecture 1 Dr. Mohsin Iftikhar Office: Cell: Lecture 1: Introduction (CSC524) : Dr. Mohsin Iftikhar

Introduction Text Book: – Computer Networks and Internets Douglas E. Comer (5 th Edition) Reference Books – Computer Networks Andrew S. Tanenbaum (4 th Edition) – CCNA ICND 1 Official Exam Certification Guide – CCNA ICND 2 Official Exam Certification Guide by Wendell Odom Lecture 1: Introduction (CSC524) : Dr. Mohsin Iftikhar

Introduction Background of Networking How Computer Networking Started Key Aspects of Networking – Network Applications and Network Programming – Data Communications – Packet Switching and Networking Technologies – Internetworking with TCP/IP – Additional Networking Concepts and Technologies Lecture 1: Introduction (CSC524) : Dr. Mohsin Iftikhar

ISO and OSI Seven Layer Reference Model International Standard Organization (ISO) – Seven Layers Model Layer 7-Application Layer 6-Presentation Layer 5-Session Layer 4-Transport Layer 3-Network Layer 2-Data Link Layer 1-Physical Lecture 1: Introduction (CSC524) : Dr. Mohsin Iftikhar

Application Layer Application layer is the top layer of OSI model which provides different kinds of services to the end-user. For example, HTTP, Telnet, FTP, SMTP are the examples of different kinds of applications. Lecture 1: Introduction (CSC524) : Dr. Mohsin Iftikhar

Presentation Layer Presentation layer is concerned with the data format. Whenever a user uses an application service being provided by the application layer, application layer passes that data written by human language to the presentation layer, presentation layer converts that data from human language to machine language (0,1) at the sending machine side and vice versa on the receiving side. Lecture 1: Introduction (CSC524) : Dr. Mohsin Iftikhar

Session Layer Session Layer is responsible for three things, it initiates the session, maintains the session during data transfer and terminates the session when the data transfer is completed. Lecture 1: Introduction (CSC524) : Dr. Mohsin Iftikhar

Transport Layer This layer performs a number of tasks – Segmentation and reassembly – Reliability through acknowledgements – Error Recovery – Flow Control through windowing – Sequencing Lecture 1: Introduction (CSC524) : Dr. Mohsin Iftikhar

Network Layer This layer provides routing. Router works on network layer. This layer is responsible for defining the end-to-end, easiest shortest possible route from source to destination. Lecture 1: Introduction (CSC524) : Dr. Mohsin Iftikhar

Data Link Layer This is the only layer, which attach header and trailer both with the data and data becomes frame at this particular layer. This layer provides error detection through Frame Check Sequence (FCS). This layer can not provide error recovery Lecture 1: Introduction (CSC524) : Dr. Mohsin Iftikhar

Physical Layer Physical layer is just concerned with the physical characteristics. For example, what type of cable to use, which pins will be used for sending the data, which pins will be used to receive the data etc. Lecture 1: Introduction (CSC524) : Dr. Mohsin Iftikhar

How Data Passes Through Layers Concept of Headers and Layers – When data comes down through the layers, each layer attach a header with it and this process is called encapsulation and on the receiving side, each layer de attach the corresponding header, which is called de-encapsulation. Concept of Protocol – Protocol is a set of rules and regulations between corresponding layers on different machines to govern the communication. Concept of Interface – Interface is always between adjacent layers on the same machine Major difference between protocol and Interface – Protocol is always between layers of different machines and interface is always between layers of same machine. Lecture 1: Introduction (CSC524) : Dr. Mohsin Iftikhar

TCP/IP Model Five Layer model: Transmission Control Protocol/Internet Protocol (TCP/IP) – Application – Transport – Internet – Network Interface – Physical Application layer of TCP/IP is corresponding to top three layers of OSI (application, presentation and session), Transport is equal to transport, Internet is corresponding to network, network interface is equal to data link and physical layer is equal to physical layer of OSI model. Lecture 1: Introduction (CSC524) : Dr. Mohsin Iftikhar

Some More Concepts Encapsulation De-encapsulation Different types of Applications at different layers Examples of application, transport and internet layer Questions Lecture 1: Introduction (CSC524) : Dr. Mohsin Iftikhar