Lecture 21 Access Methods and Internet working, Access Network Architectures Access network characteristics, Differences between Access Networks, Local Area Lecture 22 Networks and Wide Area Networks. Lecture 23 Access Technologies Lecture 24 Voice grade modems, ADSL Lecture 25 Cable Modems, Frame Relay. Lecture 26 DNS: Domain Names. Resolving Domain Names to IP addresses (DNS operation ) Lecture 27 Registering Domain Names and solving Domain name disputes. Lecture 28 Routing: How the key IP routing protocols (OSPF) Lecture 29 Routing: How the key IP routing protocols (BGP4) Lecture 30 Implications of future Internet growth on routing protocol performance. Lecture 31 Internet applications: FTP Lecture 32 .FTP implimentation Lecture 33 Internet applications: Telnet, Email, Chat Lecture 34 World Wide Web: HTTP protocol. Lecture 35 HTTP protocol Implementation and issues Lecture 36 Search Engines. E-Commerce and security Lecture37 Security : symmetric and asymmetric key Lecture 38 Encryption and digital signature, and authentication Emerging trends, Internet telephony, virtual reality over the web, etc. Intranet and Lecture 39 extranet, firewall. Emerging trends, Internet telephony, virtual reality over the web, etc. Intranet and Lecture 40 extranet, firewall.
Module I (10 lecture) Internet overview The Internet is a giant network of networks. • A network may include PCs, and other devices like servers or printers. • A network is connected through a communication channel. • Early research was performed by the US Department of Defense in 1962. This research group established ARPAnet (Advanced Research Project Agency) in order to connect the US Defense Department network. What did the Internet come from? • Original aim was to create a network that would allow users of a research computer at one university to be able to ‘talk to’ research computers at other universities. • A side benefit of ARPAnet’s design was that, because messages could be routed or rerouted in more than one direction, the network could continue to function even if parts of it were destroyed in the event of a military attack or other disaster. • The users of the Internet took a direction of their own. History of the Internet • The first long distance communication took place in 1965 between a computer in MIT and California. • In 1969, four computers clients were connected together via ARPAnet. How old is the Internet ? • Leonard Kleinrock is accredited with the idea of packet switching, which describes how data can be sent across a network. The Ethernet was developed by Xerox during this period. This was inspired by Robert Metcalfe’s PhD on ‘packet networks’. • An Ethernet is a protocol for describing how computers can be connected in a LAN (Local Area network).
• Through the use of Ethernet and ARPAnet the US were able to develop a working network. • In the late 1970s and early 1980s other networks were developed, e.g. CSNET, USNET and BITNET. In 1973 Vint Cerf and Bob Kahn created the TCP/IP communication protocols. • TCP/IP: Transfer Control Protocol/Internet Protocol is a set of rules that describe how computers can communicate over a network. • To send information over the Internet, a computer packs data into Internet Protocol (IP) packets and labels them with the correct address. They are then sent across a packet switched interconnected network. Introduction to Data Communication The term telecommunication means communication at a distance. The word data refers to information presented in whatever form is agreed upon by the parties creating and using the data. Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable. Computer Network A network is a set of devices (often referred to as nodes) connected by communication links. A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network. Software modules in one system are used to communicate with one or more software modules in the distance System. Such interfaces across a distance are termed as “peer-to-peer” interfaces; and the local interfaces are termed as “service” interfaces. The modules on each end are organized as a sequence of functions called “layers”. The set of modules organized as layers is also commonly called a “protocol stack”. Over the years, some layered models have been standardized. The ISO Open Systems Interconnection (ISO/OSI) layered model has seven layers and was developed by a set of committees under the auspices of International Standards Organization (ISO). Classification of Computer Networks
1.Based on Transmission Mode Transmission mode defines the direction of signal flow between two linked devices. There are three types of transmission modes. Simplex In simplex mode, the communication is unidirectional. Among the stations only one can transmit and the other can only receive. Half-Duplex In half-Duplex mode, the communication is bidirectional. In this both station can sent and receive but not at the same time. Full-Duplex In Full-Duplex mode, both stations can transmit and receive simultaneously. 2. Based on Time in Transmission Type • Synchronous Transmission In synchronous Transmission both the sender and the receiver use the same time cycle forthe transmission. We send bits one after another without start/stop bits or gaps. It is the responsibility of the receiver to group the bits. Bit stream is delivered with a fixed delay and given error rate. Each bit reaches the destination with the same time delay after leaving the source. • Asynchronous Transmission In Asynchronous Transmission we send one start bit at the beginning and one stop bit at the end of each byte. There may be a gap between each byte. Bit stream is divided into packets. Packets are received with varying delays, so packets can arrive out of order. Some packets are not received correctly. 3. Based on Authentication • Peer to Peer Connection In peer-to-peer networks, there are no dedicated servers. All the computers are equal and, therefore, are termed as peers. Normally, each computer functions as both a client and a server. No one can control the other computers.