PDF | On Nov 15, , Yekini Nureni and others published DATA COMMUNICATION & NETWORKING. This tutorial gives very good understanding on Data Communication and of expertise in knowing DCN, from where you can take yourself to next levels. DATA. COMMUNICATIONS. AND. NETWORKING. Fourth Edition. Behrouz A. Forouzan. DeAnza College with. Sophia Chung Fegan. #. Higher Education.
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Technologies related to data communications and networking are among the MD DALIM 01/07/12 CYAN MAG YELO BLACK fastest growing in our. Instructors and students using Data Communications and Networking, Fourth Edition by Behrouz A. Forouzan will find a wide variety of resources available at. Data communications are the exchange of data between two devices via some . Network security issues include protecting data from unauthorized access.
Network Types: A networked office building, school, or home usually contains a single LAN, though sometimes one building will contain a few small LANs perhaps one per room , and occasionally a LAN will span a group of nearby buildings.
The communication speed is from 10 Mbps to Mbps Mega bits per second. A MAN is typically owned and operated by a single entity such as a government body or large corporation. A WAN spans a large geographic area, such as a state or country.
The world's most popular WAN is the Internet. Network Structure:. In this type of network no computer is set a dedicated server but all the computers can act as a client and can act as a server. This network is used in smaller network having number computers less than It can not be used for larger networks. It is not used for database applications. Server Based Network: In this type of network one computer is act as a server and remaining all the machines act as clients.
The server will provide data and clients will get data from the server. The server is operated by the network operating system also it has faster CPU and large disk space and memory size. This network can be used for large networks. The network is more secure. It is difficult to install the network.
The cost of the network is high. Network Topology: Topology is the arrangement of computers, cables and connecting devices in a network. There are four different types of topologies, they are.
Star Topology: In this topology, all terminals are connected to a central computer, server or hub. The star topology reduces the chance of network failure by connecting all of the systems to a central node. Easy to detect faults and to remove parts. There is no possibility of data collision. More computers can be easily added to the network. It requires dedicated server.
If server fails entire network gets collapsed. It is more expensive to install. It requires large amount of cable. Bus Topology In this topology all terminals are connected to common cable called as a bus. This topology may have problems when two clients want to transmit at the same time on the same bus. Commonly has a slower data transfer rate than other topologies. It is not expensive to install. It is easy to expand the network. It is difficult to detect cable fault.
It does not require dedicated server. Ring Topology: In this type of network topology all the nodes computers are connected in a circular series of a cable. It uses less amount of cable.
It gives consistent performance in case of heavy traffic.
In case of node failure entire network fails. It is very difficult to detect fault. Mesh Topology: In a mesh topology, each of the network computer and other devices, are interconnected with one another. Every node not only sends its own signals but also relays data from other nodes.
In fact a true mesh topology is the one where every node is connected to every other node in the network.
This type of topology is very expensive as there are many redundant connections, thus it is not mostly used in computer networks.
This topology can withstand high traffic. So data transfer doesnt get affected. Even administration of the network is tough. Two insulated copper wires are twisted each other in a helical form. There are 4 pairs 8 cables of cable inside the main cable. The cables are twisted to reduce electro magnetic interference.
These cables are used in telephone system, private exchange and LAN. Coaxial cable is an electrical cable with an inner conductor surrounded by a flexible, tubular insulating layer, surrounded by a tubular conducting shield. The cable can not have electro magnetic interface. A fiber-optic system is similar to the copper wire system that fiber- optics is replacing. The difference is that fiber-optics use light pulses to transmit information down fiber lines instead of using electronic pulses to transmit information down copper lines.
At one end of the system is a transmitter. This is the place of origin for information coming on to fiber-optic lines. The transmitter accepts coded electronic pulse information coming from copper wire. It then processes and translates that information into equivalently coded light pulses. The cable has high bandwidth and data rate up to 2Gbps.
Wireless Media: In this type of network, connection is established using high frequency radio signals, Infrared signals or microwaves. The computers in the network use a transceiver antenna to transmit and receive information. Network Hardware:. Modem is used to convert the analog signal into digital and digital signal into analog as the computer does not understand analog signal, only understands digital binary signal. Modulation is a process of converting analog signal into digital.
Demodulation is a process of converting digital signal into analog. There are two type of modems, a. Internal Modem. Internal modems are placed inside the computer.
External Modem. External MODEM is a separate device, which is connected externally to the computer through a serial port. A hub joins multiple computers together to form a single network segment.
On this network segment, all computers can communicate directly with each other. A hub contains multiple ports.
When a data arrives at one port, it is copied to the other ports so that all segments of the LAN can see all data. A hub runs in half-duplex mode, means allowing each machine either to send or receive at any given time.
A networking switch is the central device in a wired or wireless LAN. It receives signals from each computer on the network cables in a wired network or radio waves in a wireless network. A networking switch runs in full-duplex mode, meaning a machine on the LAN can receive and transmit data simultaneously.
Network bridges are used to connect two similar networks. It can also be used to connect two similar network. A bridge reads the address of all the signals it receives and according to the address, it decides appropriate route for the signal. Router is a device that forwards data packets along networks. Routers are located at gateways, the places where two or more networks connect. Routers use headers and forwarding tables to determine the best path for forwarding the packets, and they use protocols to communicate with each other and configure the best route between any two hosts.
Network Protocols: A communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommunications. When a message is ready to be sent over the internet, the TCP protocol breaks its up into small packets. Each packet is then given a header, which contains the destination address.
The packets are then sent individually over the internet. The IP Protocol guides the packets so that they arrive at the proper destination. Once reached at destination, the TCP resembles the packets into the original message. TCP is responsible for breaking data down into IP packets before they are sent and for assembling the packets when they arrive.
The Application layer which provides services directly to the users such as Email, File transfer etc. The purpose of Transport layer is to permit devices on the source and destination hosts to carry on a conversation. It verifies correct packet arrival. Internet layer pack data into data packets known as IP datagram, which contain source and destination address IP address information that is used to forward the datagram between hosts and destination.
The Network Layer: Network Access layer defines details of how data is physically sent through the network, including how bits are electrically or optically signaled by hardware devices that interface directly with a network medium, such as coaxial cable, optical fiber, or twisted pair copper wire. System Control Transmission Protocol: User Datagram Protocol: The purpose of OSI model is to show how to facilitate communication between different systems without changing the hardware or software.
There are seven layers in OSI model. Application Layer: Pesentation Layer: The presentation layer which provides services to translate, encrypt and compress data. Session Layer: The session layer tracks connections, also called sessions. The session layer should keep track of multiple file downloads from a web server. This layer establishes, manage and terminate sessions. Transport Layer The purpose of Transport layer is to permit devices on the source and destination hosts to carry on a conversation.
Network Layer Network Access layer defines details of how data is physically sent through the network, including how bits are electrically or optically signaled by hardware devices that interface directly with a network medium, such as coaxial cable, optical fiber, or twisted pair copper wire.
Data Link Layer: The data link layer organizes the pattern of data bits into frames before transmission. Physical Layer:. The Physical layer is responsible for the ultimate transmission of data over network communications media. It operates with data in the form of bits that are sent from the Physical layer of the sending source device and received at the Physical layer of the destination device. Hubs and Cables are a part of the Physical layer.
At the Physical layer, data are transmitted using the type of signaling supported by the physical medium such as electric voltages pulses , radio frequencies or light rays.
The Internet is a global system of interconnected computer networks that use the standard Internet protocol to serve billions of users worldwide. It is a network of networks that consists of millions of private, public, academic, business, and government networks, of local to global scope, that are linked by a broad array of electronic, wireless and optical networking technologies. Access service offers large organizations LAN users a direct access to Internet with dedicated high-speed connection and unlimited access.
Evermore, Internet Dedicated Access provides domain names and static IP addresses to enable you to host your own corporate email and web servers. Dial-up connections to the Internet require no infrastructure other than the telephone network. Where telephone access is widely available, dial-up remains useful. Dial-up is often the only choice available for rural or remote areas, where broadband installations are not prevalent due to low population density, and high infrastructure cost.
Dial-up access may also be an alternative for users on limited budgets.
There are three types of dialup connections. The browser Lynx is used in shell account.
In this account you can see only plain text on your screen; no images or videos. It is also called as student account. In this account you can see text, image and videos. A graphical browser like internet explorer is required.
With a web browser, one can view web pages that may contain text, images, videos, and other multimedia. A web browser is a software application for retrieving, presenting, and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier URI and may be a web page, image, video, or other piece of content.
Hyperlinks present in resources enable users easily to navigate their browsers to related resources. E-mail electronic mail is the exchange of computer-stored messages by telecommunication. Through Email you can also send non-text files, such as graphic images and sound files, as attachments.
E-mail was one of the first uses of the Internet and is still the most popular use. A large percentage of the total traffic over the Internet is e-mail. Email service provider ESP is an organization which provides email servers to send, receive, and store email for the general public. Mail, Hotmail, Gmail, and many others. An ESP's services are typically paid for by subscription, as part of membership, or through advertising.
IP Address: Internet Protocol Address: An IP address Internet Protocol address is a logical address of a network adapter, and each and every network device has one. An IP address is a unique series of numbers that identifies computers on a network, so an IP address can easily be used to determine the location of a device or origin of an internet message. It is a 32 bit number. A weblog, sometimes written as weblog, is a Web site that consists of a series of entries arranged in reverse chronological order, often updated on frequently with new information about particular topics like images, audio or video.
The weblog seems popular because the viewer knows that something changes every day, there is a personal point-of-view, and, on some sites, there is an opportunity to collaborate or respond with the Web site and its participants.
Weblog analyzes a Web site's access log and reports the number of visitors, views, hits, most frequently visited pages, and so forth.
Domain Name is an Internet service that translates domain names into IP addresses. Because domain names are alphabetic, they're easier to remember. The Internet however, is really based on IP addresses. Every time you use a domain name, therefore, a DNS service must translate the name into the corresponding IP address.
For example, the domain name www. Domain Names: The three or two letter code indicating whether the address is a business. For end user domain names are in text format because it is easy to remember but for computers it is in number form IP Address. The DNS is converting this text format to number format. In computing, a uniform resource locator or universal resource locator URL is a specific character string that constitutes a reference to an Internet resource.
Searching the Web: Search Engines: Search engines are programs that search documents for specified keywords and returns a list of the documents where the keywords were found. A search engine is really a general class of programs, however, the term is often used to specifically describe systems like Google, Bing and Yahoo!
Search that enable users to search for documents on the World Wide Web. There are different types of searches, they are a Advanced Search Advanced Search allows you to filter your search using specific parameters in order for you to receive results that are more accurate. Don't have an account? Create an account now. Submit a Request. Get order and invoice support. Outside the United States: Contact International Customer Support.
Hours of Operation: Submit a Support Request. Locate contact information for your U. Sales Rep Get Started. Order and Invoice Support Please Note: In our effort to protect our customer's data, we will no longer take or store credit card data in any manner within our systems.
As of April 30, we will not accept credit card payments via e-mail, fax or standard mail. Please note, when contacting via phone it is not secure to leave credit card information on voice mail.
We take our customers' security seriously and believe that this approach is in the best interest to protect our customers and our company alike.