Ch1 (1).pdf

Computer Network Systems: ICS-432 Chapter 1 Introduction Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1.0././././  1-1 DATA CO...

Computer Network Systems: ICS-432 Chapter 1 Introduction Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1.0././././  1-1 DATA COMMUNICATIONS 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. Topics discussed in this section: Components Data Representation Data Flow 1.0  Figure 1.1 Five components of data communication Protocol: is a set of rules that govern data communications. It represents an agreement between the communicating devices. 1.0  Data Representation Information today comes in different forms such as: text numbers images audio video 1.0  Figure 1.2 Data flow (simplex, half-duplex, and full-duplex) Communication between two devices can be simplex, half-duplex, or full- duplex as shown. 1.0  NETWORKS 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. Topics discussed in this section: Distributed Processing Network Criteria Physical Structures Network Models Categories of Networks Interconnection of Networks: Internetwork 1.0  Figure 1.3 Types of connections: point-to-point and multipoint Point-to-point connection: provides a dedicated link between two devices. Multipoint: more than two specific devices share a single link. 1.0  Figure 1.4 Categories of physical topology Physical topology: refers to the way in which a network is laid out physically. 1.0  Figure 1.5 A fully connected mesh topology (five devices) Advantages: How many links are Dedicated links required for a full mesh Robust Privacy and security topology with 6 devices? Fault identification easy Disadvantages: The amount of cabling and the number of I/O ports required. How many ports are required for a full mesh topology with 6 devices? 1.0  Figure 1.6 A star topology connecting four stations Advantages: Less expensive than mesh. If one link fails, only that link is affected. Disadvantage: Dependency of the whole topology on one single point. 1.0  Figure 1.7 A bus topology connecting three stations Advantages: Ease of installation. Disadvantage: Difficult reconnection and fault isolation. 1.0  Figure 1.8 A ring topology connecting six stations Each device has a dedicated point-to-point connection with only the two devices on either side of it. Advantages: Ease of installation( immediate neighbors). Disadvantage: Difficult reconnection and fault isolation. 1.0  Figure 1.9 A hybrid topology: a star backbone with three bus networks 1.0  NETWORK TYPES Local area network ( LAN) Wide area network (WAN) Metropolitan Area Network (MAN) Personal Area Network( PAN) Others like SAN and VPN…. 1.0  Figure 1.10 An isolated LAN connecting 12 computers to a hub in a closet 1.0  Figure 1.11 WANs: a switched WAN and a point-to-point WAN 1.0  Figure 1.12 A heterogeneous network made of four WANs and two LANs 1.0  Switching An internet is a switched network in which a switch connects at least two links together. A switch needs to forward data from a network to another. Switched Networks: 1. Circuit switched network 2. Packet switched network 1.0  Circuit Switched Network: a dedicated connection, called a circuit, is always available between the two end systems; the switch can only make it active or inactive. Circuit switched network 1.0  Packet-Switched Network: the communication between the two ends is done in blocks of data called packets. Packet-Switched Network 1.0  THE INTERNET The Internet vs an internet ! The Internet has revolutionized many aspects of our daily lives. It has affected the way we do business as well as the way we spend our leisure time. The Internet is a communication system that has brought a wealth of information to our fingertips and organized it for our use. 1.0  Figure 1.13 Hierarchical organization of the Internet 1.0  Accessing the Internet We need to be physically connected to an ISP: 1. Using Telephone Networks (Dial-up and DSL). 2. Using Cable Networks. 3. Using Wireless Networks. 4. Direct Connection to the Internet. 1.0