Chapter 1: Introduction to Computer Networks and Data Communications

Chapter one is literally an introduction to computer networks and data communications. Curt M. White, author of the text, introduces the readers to various concepts of networks and data communications. These concepts include: the language of computer networks, the big picture of networks, common examples of communications networks, convergence, and network architectures. White starts with the language of computer networks to help the reader gain a better understanding and to help with the emphasis of the textbook.

Language of Computer Networks:

The first concept White discusses is the language of computer networks. According to the author, computer networks is "an interconnected group of computers and computing equipment using either wires or radio waves that can share data and computing resources" (White, 3). Within this group of interconnected computers and computing equipment, there are various different types of networks. These networks include: personal area networks (PANs), local area networks (LANs), campus area networks (CANs), metropolitan area networks (MANs), and wide area networks (WANs). Another network that has become popular today is the cloud based network. Cloud based networking is only the storage of data or information on the internet in a remote location rather than storing the information or data on a local drive. An example of this is Google's Google Drive application. Google Drive lets the user store a certain amount of data or information on the internet, which they secure of course. This will give the user the ability to use any device and download the user's files onto that device as long as they enter the correct credentials for the account. The text explains that there are two important building blocks to understanding computer networks. The two important concepts are data and signals. Data is "information that has been translated into a form more conducive to storage, transmission, and calculation" (White, 4). This just means that the data is converted in a way to make it more acceptable to store, transmit, and calculate. Signals are used to transmit the data or information. This is normally described as data communications, "the transfer of digital or analog data using digital or analog signals" (White, 4). The author then explains what we must do in order for users to connect any device to a computer network. White only gives the reader a brief explanation what the term is to connect a device to a computer network which is, interfacing. The section moves onto two ways of transmitting signals efficiently. These two ways consist of multiplexing, which is the "transmission of multiple signals on one medium," and compression, which "squeez[es] the data into a smaller package... reducing the amount of time needed to transmit the data" (White, 4). The section then ends with a discussion on the term convergence. Convergence is the merging of data network and voice network. Voice network transmitted telephone signals, while data network transmitted computer data. What convergence means is that voice network is now transmitting telephone data rather than telephone signals. The next concept that is considered is the big picture of networks. 

The Big Picture of Networks:

The author gives the reader an overview of what an actual set of networks would look like. White combines both the WAN and LAN together to give us a better idea of how everything works together. According to White, LANs require hardware such as workstations, servers, switches, and routers. WANs consist of nodes, high-speed transmission line, and subnetworks. In order for any user to request any kind of information from web servers, the individual must have both the "necessary hardware and software" to communicate with WANs. The user also needs a modem to connect to the web page as well. Another requirement is software to enable a computer to "speak" the language of the internet which is TCP/IP. TCP/IP or also known as Transmission Control Protocol/Internet Protocol, is a process of sending and receiving data packets through various steps. 

Common Examples of Communications Networks:

This section explains various ways users connect to networks on a day-to-day basis. These examples include desktop computers connecting to the internet, laptop computers connecting to wireless connections, cell phone systems, and various other means of common networks. There are also sensor networks, satellite and microwave networks as well. 

Convergence:

The convergence concept was explained earlier in the text. This concept is the combination of voice networks and computer networks. White discusses the three different types of convergence, which are the technological convergence, protocol convergence, and the industrial convergence. An example of the technological convergence is the transmission of voice networks through data transmission. Instead of sending voice signals, we now transmit voice through data packets. This is called Voice over Internet Protocol (VoIP). Other examples can be photos that are sent over the internet like SnapChat. 

Network Architectures:

This section explains the two most common network architectures, or also considered as communications models. The two most common of these models are the TCP/IP protocol suite and the Open Systems Interconnection (OSI) model. The TCP/IP protocol suite was created by a group of scientists to support a new kind of network which was called the ARPANET. This network was being installed across the US through the 1960s and the 1970s. The protocol has designed and based on a number of layers. This protocol consists of five layers for the user to connect to; the application layer, transport layer, network layer, network access layer, and the physical layer. When all layers are operating correctly, their jobs are to send data over a network of computers and to ensure the quickest route possible through the network of computers. The first layer is the application layer. There are various applications that are used which are hypertext transfer protocol (HTTP), simple mail transfer protocol (SMTP), file transfer protocol (FTP), telnet, and simple network management protocol (SNMP). The text explains that a common example of an application would be an e-mail. E-mails send and receive messages throughout the day. The application layer will ask the user to enter the message he or she would like to send to another user over the network. The application layer would then create a data packet that consists of the message and the address of the intended receiver. Once this job is completed, the application layer will send the contents to the transport layer. The transport layer's responsibility is to ensure transport integrity. This layer is supposed to establish a connection, monitor flow between sender and receiver, and retrieve any lost data that went missing during transportation. The next layer is the network. This layer would take the packet and add routing information so the information will find its way through the network. After the network layer, the network access layer would insert error-checking information and prepare the package for transmission. The final layer is the physical layer, which this layer's job is to actually transmit the data packet over wire transmission or wireless transmission. 

The second common network architecture is the OSI Model. The OSI model consists of seven layers. There is the application layer, presentation, session, transport, network, data link, and the physical layer. The presentation layer will perform various functions that will sometimes be needed when presenting the data package to the receiver. These functions include character conversions, encryption and decryption of documents, and compression of data. The session layer is responsible for establishing sessions between various users. The session layer can consist of a token management software or will establish synchronization points. Another layer the TCP/IP protocol does not have is the data link layer. The data link layer is similar to the transport layer of the TCP/IP protocol. This layer will take the data from the network layer and transform it into a "frame." All other layers within the ISO model are similar to the TCP/IP protocol suite. Two other terms are discussed which are the logical connections and the physical connections. Logical connections are nonphysical connections between sender and receiver that allows an exchange of commands and responses. For example, application layer will have a logical connection with the receiver’s application layer. Physical connections are direct connections between the sender and the receiver. This is the connection where the 1s and 0s are actually transmitted over wires or airwaves. This will only happen with the physical layer.