Lecture1 introductiontonetwork
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The document provides an overview of computer networks. It defines a computer network as an interconnected collection of autonomous computers. It uses the example of the Internet, which interconnects millions of computing devices worldwide running network protocols to communicate. Devices are connected through intermediate routers using communication links like cables, wireless connections, or radio spectrum. The Internet is a network of networks that must all run the IP protocol. Advantages of networks include resource sharing, communication, robustness, cost efficiency, and reliability. Networks also have different communication modes like simplex, full duplex, and half duplex, and different link types like point-to-point and multipoint.
Lecture1 introductiontonetwork
- 1. Lecture 1 Network Network is defined as an interconnection of different entities. When the entities are Human- We call it as Social Network Telephone- We call it as Telephone Network Computer- We call it as Computer Network We will talk about Computer Network in this subject, and there will be few examples and citations from Telephone Network (because whole network is based on telephone network). We define Computer Network as the interconnected collection of autonomous computers. To understand what computer Network is, we will use the example of public Internet, a specific omputer network, which most of the readers must have used by now. We will describe the internet in terms of networking infrastructure as shown below. The Internet is a world-wide computer network, i.e., a network that interconnects millions of computing devices throughout the world. Most of these computing devices are traditional desktop PCs, Unix-based workstations, and "servers" that store and transmit information such as WWW pages and e-mail messages. In the Internet jargon, all of these devices are called hosts or end systems.
- 2. Whenever we want two entities to communicate we require a medium, when we human beings communicate, medium is air. If there is no air, means vacuum, we will not be able to hear each other or in other words, we will not be able to communicate. Similarly, for two computers or end systems to communicate a medium is required or a communication link which can be wired or wireless. We'll see later and have already discussed in the first week of class about many types of communication links. Links are made up of different types of physical media: coaxial cable, copper wire, fiber optics, and radio spectrum. There can be a wireless link i.e. end systems are communicating through air, such a network is called as wireless network and if there is a physical link present between entities in a network, then the network is called as wired network. Different links can transmit data at different rates. End systems, as well as most other "pieces" of the Internet, run protocols that control the sending and receiving of information within the Network. Protocol is a set of rules, so we can say that end pieces or hosts or nodes are running protocols and they adhere to these protocols for communication. Infact majority of computer network subject deals with the study of protocols or network protocols. We will discuss about protocols in further classes. Usually, end systems are not directly attached to each other via a single communication link. Instead, they are indirectly connected to each other through intermediate switching devices known as routers. A router takes information arriving on one of its incoming communication links and then forwards that information on one of its outgoing communication links. The path that transmitted information takes from the sending end system, through a series of communications links and routers, to the receiving end system is known as a route or path through the network. The Internet is really a network of networks. That is, the Internet is an interconnected set of privately and publicly owned and managed networks. Any network connected to the Internet must run the IP protocol and conform to certain naming and addressing conventions Advantages of Computer Network 1. Resource Sharing 2. Communication 3. Robustness 4. Cost Efficient 5. Reliability Communication Modes Network device communicate in either one of the three listed modes. These modes define the property of Network devices. • Simplex can be viewed as a communications "one-way street". Data only flows in one direction. That is to say, a device can be a receiver or a transmitter exclusively. A simplex device is not a transceiver. A good example of simplex communications is an FM radio station and your car radio. Information flows only in one direction where the radio station is the transmitter and the receiver is your car radio. Other examples are keyboard wire or Video screen wire.
- 3. • Full Duplex communications overcome the limits of Simplex communications by allowing the devices to transmit in both the directions. Full Duplex devices can transmit and receive data at the same time. For example: telephonic conversation • Half Duplex devices allow both transmission and receiving, but not at the same time. Essentially only one device can transmit at a time while all other half duplex devices receive. For example walky talky or lift. Types of Link 1. Point-to-Point Communication 2. Multipoint Link Point-to-Point link means direct connection of two devices, for example serial port or parallel port. Multipoint link means multiple devices connected to the same link.