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Chapter – 1
Data Communication & Network
COMMUNICATION : - Communication in general means to convey some message, audio, video, pictures etc. It should be clearly understood by the recipient or to whom it has been conveyed and the recipient should be able to the clearly understood it and must also be able to respond.
Methods Of Conveying Messages : - (1) By speaking loudly: - It the distance is not far away. (2) By Peon: - If the message has to be send with in an office. (3) By Post (Mail): - It the message has to be sending with in the same city or in another city. (4) By Phone
Advantage of Telephonic Communication : - (1) It is instances. (2) It is cheapest with in a city. (3) It is reliable as you become able to listen the voice of the recipient.
Disadvantages : - (1) It’s costly outside the city. (2) Both sender and receiver must be present at the same time. (3) Both sender and receiver must have the telephone connection. (4) Both sender and receiver must able to speak and understand the same language. (5) Written messages cannot be sending along with telephone. (6) Telephonic conversation cannot be used as evidence. (7) Telephonic conversation can be easily taped.
Electronic Method of Communication Advantages : - (1) It does not require any special equipment as it can be made through existing phone line. (2) Written messages can be easily send and which can be used as evidence. (3) Pictures, videos and programs can also be sending. (4) It is cheapest. (5) Communication can be made to any part of the globe at the same expense, as a local call made with in a city. (6) It is totally secured because the message becomes in electronic pulses (0, 1). (7) For the electronic method of communication is not necessary must present at the same time. (8) For the electronic method of communication it’s not necessary that both sender and receiver must speak and understand the same language.
Transmissions Media : -Media used for electronic communication can be as follows: -
- Bounded Media
- Unbounded Media 1. Bounded Media : - In the case of bounded media the data can be sent in a limited space.
Types of Bounded Media : - (a) UTP (Unshielded Twisted Pair Cable) (b) Co-Axial Cable (c) STP (Shielded Twisted Pair Cable) (d) Fiber Optics Cable.
(a) UTP : - Characteristics of UTP : - (1) UTP cable consists of two copper wires. (2) Pairs twist wires together to reduce the electrical interference from the close. (3) Wires are twisted together in a helical form. (4) These wires are commonly used for digital data transmission over a short distance. (5) Data transmission speed of UTP cable is approx 9600 BPS (bits per sec).
(b) STP : -These wires are broadly used in telephone networks and for digital communication. These wires are typically used in electrically noisy environment to limit the effects of noise absorption.
(c) Co-Axial Cable : - Cable T.V. operators use it. Generally it becomes a group of specially insulated wires, which are able to transmit data at the higher rate. This wire is surrounded by PVC (Polly Vinyl Chloride). The inner central copper wire transmits the signals and it is again electrically sealed by outer metal sleeve. Advantages : - (1) It can carry high frequency comparing to twisted pair cables that’s why it is suitable for telephonic conversation. (2) It can carry 12000 telephone calls simultaneously. (3) It offers higher noise immunization and can offer clean & clear data transmission. (4) There is no chance of error or loss of signals. (5) Such cables are generally used for connecting two near building maximum with in 1 Km’s.
(d) Fiber Optics Cables : - These are the fastest communication medium. fiber optics cables use semi conductor laser to transmit the information in the form of light along with thin hair like fibers at the speed of 38600 miles per second. Advantages : - (1) They are lighter, stronger then copper wires. (2) They offer higher bandwidth comparing to microwave transmission. (3) They are very much secured because they are not affected from electro magnetic interference. (4) They offer low error rate. (5) Under water communication is also possible with fiber optics. (6) They can even operate on a very high temperature that could melt other wires.
2. Unbounded Media : - In the case of unbounded media the data can be sent in an unlimited space. Type of Unbounded Media: -
Network of Topology : - The way workstations are arranged or connected in a network is known as network of topology. Types of topologies: - (1) Linear / Bus / Ethernet (2) Star / Hub / Arcnet (3) Token ring (4) Mesh topology
(1) Linear / Bus / Ethernet : - In bus topology one or more multiple primary stations (server) can be used with which multiple workstations (Nodes) can be attached. These workstations are attached with the primary stations by the help of a special cable termed as bus and hence it is called bus topology. Advantages : - 1.The size of the network can be easily extended. 2.It one workstation (Node) goes down; it does not effect the whole network. Disadvantages: -
- If bus (backbone) goes down, then it results in a network failure.
(2) Star / Hub / Arc net : - In star topology all the workstations are connected through a central point that’s why it is known as star topology. Advantages : - (1) Any workstations can be easily added or removed. (2) If one workstation goes down, it does not affect the whole network. (3) Signals amplifications through the hub. (4) It offers a distance of up to 200 feet between the workstation and the hub. Disadvantages : - (1) If the hub goes down, it results in a network failure. (2) If the size of the network has to be increased, then one may require purchasing a new hub.
(3) Token Ring : - Ring top forms a ring like structure where all the workstations are connected with a single wire with each other. Advantages : - (1) There is no requirement of server. (2) Faster data transmission. (3) Some times it looks cheaper. Disadvantages : - (1) It not easy to add or remove workstations. (2) If one workstation goes down then it result in at least half portion of network failure (Network Break Down).
Mesh Topology : - This topology is a mixture all the above discuss topology.
Network : - A network is a group of people sharing some information as in a same way a group of computers connected with each other sharing some information or resource is known as network.
Types of Network : - Network can be classified in the following 5 categories: -
(1) LAN (Local Area Network) (2) CAN (Campus Area Network) (3) MAN (Metropolitan Area Network) (4) WAN (Wide Area Network) (5) VWAN / GAN (Very Wide Area Network / Global Area Network)
Advantage of Networking: - (1) Any piece of information can be shared with each other. (2) Costly resources can also be shared between several computers e.g. massive storage devices (Hard Disk), laser printer, processor (CPU) etc. (3) It increases timeliness. (4) Increased productivity. Disadvantages of Networking: - (1) Financial cost networking is will higher. (NIC and RAM are required in every node) (2) Network software requires some amount of memory space in of the connected nodes. (3) By networking we add one more level of complexity for the computer operator. (4) Some control on the part of the user is lost. (5) Many applications or programs may not work in network environment e.g. Tally, CorelDraw etc.
Features of LAN: - (1) It is a local area network or we can say a private network owned by a single person. (2) Its range is up to 10kms. (3) It is usable to connect PC in two buildings in shorter distance. (4) LAN allows sharing of expansion resources like higher storage device (Hard Disk), laser printer, ink-jet printer etc.
Features of CAN: - (1) Its range very from 10 to 20 kms. (2) It mostly covers the whole campus of a university, army camp etc.
Features of MAN: - (1) It can be public or private network. (2) It mostly covers the whole city e.g.: -Cable T.V. network.
Features of WAN: - (1) It is a public network, as its name suggests it can work up to wide space that is it can be used to connect different cities.
Features of VWAN: - (1) It is also a public network. (2) It is used for connecting different countries or around the globe.
Microwave Transmission : - ( 1) Terrestrial Microwave System (2) Infra Red and Millimeter Wave Transmission
comparing to synchronous. In synchronous there becomes a priority bit for error detection.
In asynchronous there is no such facility.
Synchronous is more suitable for digital data transmission.
Asynchronous is suitable for or analog data transmission. Synchronous the system resources or the transmission line does not remain in ideal state.
Asynchronous the system resources & transmitted line sometimes remains in ideal state.
Asynchronous Data Transmission : - In Asynchronous Data Transmission the data is transmitted character by character in irregular intervals that’s why it is known as start stop transmission because of its nature that is the sender can send a character at any time convenient to him & receiver accepted and them the line go in ideal state until the hardware on the line is not ready for transmission. Since the line becomes in ideal state a series bits has to be send to the receiving node (work station), to notify that some data is coming and when data is finished the node has to notify again that transmission is completed and again go back to idle state hence the stop bits are to be send.
Synchronous Data Transmission : - In this there is no concept of start & stop bit so, the codeclinations between two nodes that is between the sender and the receiver is handled differently. In the data is transmitted blocks (group of characters) somewhat in a packet of memory and then each block is formed by hence and trailer information. The hence block of character contains to actual message to be transmitted and also the address of the sender cum receiver the trailer block contains end of message character followed by a check character for detection of any error in transmission.
Band Width (Capacity) : - This is use a range of frequency available for data transmission as wider the band width of a communication system will, the more data it can transmit in a given period of time. It can be expressed in BPS/KBPS/MBPS.
OSI Layers (Open System Interconnection) : - This model is based on the proposal developed by ISO (International Standard Organization) of the protocols (set of rules and regulations) used in the various layers. This model is called as ISO-OSI reference model because it deals with connecting system, means the system which is open for communication which other system. This model has 7 layers, which refers to a system where multiple standards protocols can be used to address multiple functions of any of the layers of the model. OSI was developed in
Functions Of Different Layers Of OSI Models : -
- Physical Layer : - (a) This layer is responsible for establishing physical connection between two computers. (b) It is also responsible for transmitting information (0,1) over a communication.
- Data Link Layer : - (a) This layer is responsible for establishing node to node communication. (b) This layer is also responsible for making sure that the network is being used in orderly manner.
- Network Layer : - (a) This layer is used when their arises a need of node to node to node communication in still of a simple node to node (b) It is also responsible for controlling flow of data packets.
- Transport Layer : - (a) This layer is responsible for providing quality services and accurate delivery by performing error detection and correction. (b) It also makes sure that data is received completely and in proper order.
- Session Layer : - (a) these layers even add more rules to the other rules that are being established by the network layer. (b) It establishes formal dialogue between two nodes. (c) Session layer provide services like login process.
- Presentation Layer : -This layer presents data to the application layer. The presentation layer is supposed to give data a uniform appearance so that the application layer can easily recognize it. This layer performs tasks like data encryption, data compression and format conversion etc.
(3) EFT (Electronic Funds Transfer) (4) Batch Processing (5) Interactive Processing (6) On Line Processing (7) Real Time Processing
(1) Centralized Processing : - In this each user is connected with the main computer (Server) because a dumb terminal (node) becomes unable to perform processing on its own. The centralized processing is used where the whole data based is centralized and data retrieval can be done from any dumb terminal connected with the server. e.g.:- Railway stations, Air reservation etc.
(2) Distributed Processing : - In this method many computers are commented in a communication network and each computer is connected one another as well as with the server (if exists) E.g. Ring topology.
(3) EFT : - In this the advantage is quick access and quick transitions which are possible with in mille sec. E.g. ATM banking
(4) Batch Processing : - In this mode processing is done only when the data becomes in a group or batch. The drawback of this is that the individual user has to wait till the information of a batch in which he may have to spend or waste more time and rather some times it may be a wasteful activity only after the time has lapsed (gone). But the advantage of this is that the system resources are fully utilized for the whole group or batch and some time it seems to be more productive then other processing modes.
(5) Interactive processing : - In the case of this user interact with the computer i.e. the computer talk back with the user through the dialogue boxes having variable options available on each dialogue box and the further processing is being taken by the computer based on the input supplied by the user or the options selected by the user that means the user & the computer both cooperate with one another to carry out the processing. E.g. Many wizards provided by windows e.g. chart wizard, mail merge, pivot table wizard etc.
(6) Real Time Processing : - A real time system is one that takes input directly from the area where it is created and gives output directly at the place where it required stored data is organized in such a way that individual place of data can be retrieved or modify quickly and without necessarily accessing any other piece of data in the system. The examples of real time processing are: - i. Banking ii. Airline iii. Stock brokerage
(7) On Line Processing : - This is system controls the environment by receiving data processing them & returning the result sufficiently fast to affect the environment at that time. The time factor is very important & is generally fraction of sec.
Generally on line system interact with the people while real time system interact with the people as well as with the environment the examples of on line processing are: - i. ATM machine ii. Missile guidance iii. Process control system
files from a computer or the Internet on to your computer most of the files are downloaded using FTP. FTP is commonly referred as TCP/IP (TRANSMISSION CONTROL PROTOCOL & INTERNET PROTOCOL). It can also be used to upload files from your computer to another computer on the net. The main competition of FTP is HTTP (Hyper Text Transfer Protocol). HTTP server can do whatever FTP server can do and even can do it more efficiently numerous FTP server all over the world allow people any where in the world to login and download whatever files have been placed of the FTP server.
TCP/IP (TRANSMISSION CONTROL PROTOCOL & INTERNET PROTOCOL) : - TCP is a Protocol Stock designed to connect different networks on which the Internet is based TCP can work with any hardware or O.S. TCP is just a shorthand notation for a full protocol suite, for set of protocols that have standard ways of interacting with each other.
Some TCP/IP Members Their Functions Are As Follows: -
- TCP : - TCP ensure that connections are making and maintain between the computers.
- IP : - IP stands for Internet protocols it handles software computer addresses.
- RIP ( Routing Information Protocol) it finds the quickest route between the computers.
- OSPE ( Open Shortest Path First) it is a subordinate of RIP’S that increases speed and reliability of RIP.
- ICMP ( Internet Control Message Protocol ): - It handles errors and sent error messages to TCP/IP.
- BGP/EGP : -It stands for Boarder Gateway Protocol/Exterior Gateway Protocol it handle how data is passed between two networks.
- SNMP (Simple Network Management Protocol): - It allows network administrator to manage and connect network devices.
- PPP : - It stands for Point-To-Point Protocol. PPP is commonly used by Internet Service Provider to allow their customers to connect with their services.
- SMTP ( Simple Mail Transfer Protocol ): - it handles how e-mail is passed between servers on a TCP/IP network.
- POP3/IMAP : - It stands for Post Office Protocol Version3 / Interactive Message Advertising Protocol. These both setup ways of clients to connect with the server and collect e-mail.
- Internet Layer Protocol : - This is used for routing & providing single network interface as routing is a complex job and it has to carry out by internet layer the various protocols at the internet layer are as follows: - i. IP (Internet Protocol) ii. ARP (Address Resolution Protocol) iii. RARP (Reverse Address Reservation Protocol) iv. Boot P (Bootable Program) v. ICMP (Internet Control Message Protocol)
IP : - It is a low level protocol that route packets of data across separate networks, tide together by routers to form the Internet or Intranet. Data travel in packets called IP data grams. Limitations of IP : - a) If does not guaranty that a packet to reach to its destination. b) It has no ability to perform flow control. c) It cannot perform error correction or detection.
d) It does not guarantee that a packet will arrive in order and does not order them sequences.
ARP : - ARP interrogates the network by sending out a broad cast asking the machine with the specific IP address to reply its hardware address. ARP is able to translate software address that is the IP address into a hardware address. It is technically referred as Media Access Control (MAC) address.
RARP : - A designated machine called as RARP server response with the answer on the identify server over net..
Boot P : - It is used by diskless machine to learn the following: - a) IP address b) The IP address of the server c) The name of the file that is to be loaded into memory and executed at boot up.
RFC ( Request for Comment ): - RFC defines the functions & the service provides by each of the many Internet protocol compliance with the RFC guarantee the cross wonder compatibility.
Addressing in Internet: - An IP address is a numerical identifies assigned to each machine on an IP network. It designates the location of the device. It is assigned to on the network.
ISP (Internet Service Provider ): -An ISP is a company that provides Internet services to other companies and individuals you connects to ISP a machine. The popular ISP here in Jodhpur is: - a) Satyam online b) Wilnet online c) Data infosys etc.
Types of Connectivity : - These are several ways to connect with the Internet. The more expensive services provide more features, more flexibility and greater data transfer rate or capacity large companies choose dedicated Internet access. The smaller organizations are happy with PC dial up access.
(1) Dial Up and Termination : - This is the simplest and cheapest type of connection to the Internet. For this all you need is a computer with a modem attached with a phone line. The individual user or smaller organizations dials- in to an Internet service provider (ISP).
(2) Dedicated Internet Access : - The most popular Internet access for companies and an institution is a dedicated phone line connecting your LAN 24 hrs with the Internet.
(3) Leased Line : - When there is a need of handling large volume of mails connecting an entire network of users or offering other information services require a permanent connection with the net & higher band width then a normal modem can deliver. The solution is leased line connection to the Internet. These are fast 7 permanent depending on your bandwidth requirement; your ISP can provide leased line ranging from 24 kbps to 2MBPS. VSNL: - Videsh Sanchar Nigam limited: -
Chapter-
E- Mail and List Server
E-Mail: - It is sending messages, voice, video and graphics over digital communication link any where in the world at very cost effective rate. Technically e-mail is a type of client server application that provide a routed a stored message service between any two e-mail accounts.
Procedures of E-Mail: - there are two broad procedures of e-mail: - (1) Subscribe to some e- mail service such as yahoo.com, rediff.mail, hotmail.com etc. (2) Install your own e-mail server on the net.
Drawbacks of subscribing with some websites: -
- E-mail carrying your some important massage may fall in some wrong hands, may be in the hands of your, competitor.
- Your e-mail account some unwanted advertisement.
- Your e- mail ID is publicly flashed around the globe.
- Your e-mail account is not fully secured as you became part of some website and the publishers of that website can trick you.
Advantage of installing your own e-mail server: -
- Your e-mail is totally secured i.e. it cannot go in wrong hands.
- E-mail carrying your message will not be carrying any advertisements.
- Your e-mail ID is not publicly flashed.
- You can install your own web server.
- Initially installing your own e-mail server seems to be costly but as the volume of mails increases the overheads may not group and so the price you pay per message will automatically come down.
E-mail Networks: - The primary component of e-mail server is a “ post-office ” an area on the shared hard disk that is reserved for e-mail. This post-office serves as the central message holder as it has both “ in” and “out” baskets for each user to send a message. A link is established between the senders “out” basket and the addresses “ in” basket.
How e-mail works on the Internet: - E-mail messages are send in the same way as most of the Internet data. The TCP protocols break your message into packets and the IP protocols deliver the packets to the proper location and then TCP reassembles the message on the receivers and so that it can be read. You can also attach binary files such as pictures, videos, sounds and executable file to with your e-mail messages. Note: - The Internet is not able to directly handle binary files in e-mail. The file must be encoded in one of the variety of encoding schemes. The popular schemes are MIME & UUEN code. Much e-mail software does this automatically. MIME (Multi-purpose Internet mail extension) UUEN code (UNIX to UNIX encoding)
E-Mail Protocols: -
- X.400: - The messaging standard with the greatest international impact is called X.400. It attempts to lay down standard for all electronic messaging system in the world large scale messaging services such as CompuServe and America online use the X.400 specifications.
- SMTP (Simple Mail Transfer Protocol): - It is a part of TCP/IP protocol that specifies how computer will exchange e-mail. It works with POP and is one of the reasons that Internet e-mail functions so well it can be used only with computers constantly connected with the Internet such as an ISP. The ISP server them off load the mails to its users.
- UUCP: - UNIX to UNIX copy. It is standard UNIX utilities that manage the transmission of information or e-mails between UNIX systems using serial connection and regular telephone line.
Description of E-Mail Header: -
NAME FUNCTION
To: - E-mail of the primary recipient. CC: E-mail address of the secondary recipient to whom one copy needs to be sending. BCC: - E-mail address of the secondary recipient but the primary recipient should not know about the dispatch of the e-mail. From: The originator or creator of the mail. Sender E-mail address of the actual sender. Received: To identify the date & time when the message was receive. Return path: It can be used to identify the path back of the sender.
Additional Header: - Which are not mandatory but may be used if required. Name Function Date: Date and time the message was send. Reply to: E-mail address to which replies should be sending. In reply to: Message ID no. of the message for which this is a reply. Message ID: A unique no. identifying the message. Reference: Other relevant ID messages. Key word: It used by you. Subject: subject of the message.
E-mail Routing: - The Internet protocol delivers mails based on the specific-mail address. This address is expressed in 4 no. separated by periods (Dots) such, as 163.52.182.65 but it would be difficult to remember such a complex numbered address so Internet address are made up of words & letters Computers called Domain Name Server (DNS) translate the alphabetic address into numerical address so that e-mail can be send to the proper location if you are taking Internet facility from an ISP, then you will be sending your mails to the ISP server where it will be using the ISP’s server to translate the alphabetic e-mail address to the IP address that is in numerical form.
List Server: - In list server is an automatic mailing system available on the net. Mailing is one of the most exciting user of e-mail it connects a group of people who are interested in the same topic such as home schooling, Hollywood, bollywood, computer, environment, forecasting etc. when one person send e-mail to the mailing list, the same is send to every one in the mailing list.
CHAPTER – 4
FTP (File Transfer Protocol) : - One of the most popular uses of the Internet is the download file that is to transfer files from a computer. These are many thousands of files which are down loaded everyday from the net. Most of these files are downloaded using Internet FTP. It can also be used to up load files.
Public domain software’s: - Internet permits to download files like sample applications, digital art, music and many other offering. Software companies Promote their products by maintaining their websites where there customers can obtain samples, updates, entertainment supplies like sound, video, movies bands, and video games etc.
Free ware: - Software distributed absolutely free is called ~ .programmers of ~ does this for their personal satisfaction from their work or to gain good will (reputation).e.g. UNIX
Shareware : - This is the software that is distributed for free (some times) on trial bases. If you like the software and want to continue to use it, beyond the trial period. It your responsibility to register and pay for it e.g. LINUX.
Nag ware: - Software that reminds you to register all the time is known as ~.
Napster: -~ is a song treading free shareware program. ~ is a free windows program available to any one over the Internet the fast connection enable ~ to down load computer coded music files in as little as 10 sec.
Types of FTP servers: - ~ can be of two types: - (1) Anonymous server (2) Non-anonymous server
Anonymous server: - It is the most common use of the FTP ~. FTP servers do not require a password to access you only have to login and it treats you e-mail address as password.
Non-Anonymous server: - The other forms of FTP server which require both e-mail address & Password to access.
Modes of downloading files on FTP: - (1) ASCII mode (2) Binary mode
ASCII mode: - the ~ is used for downloading text files.
Binary mode: - It is used for downloading binary files & the files through untouched. The files are downloaded from the server to your computer via the data connection after the file is downloaded, the data link automatically closes. When the files are downloaded and the data link closes the command link stay open. You can then change the dir or download more files after you have done, you log off & command link closes. You are no longer connected to FTP server.
CHAPTER – 5
Telnet (TELecommunication NETwork)
Introduction: - Telnet stands for telecommunication network. It is a virtual terminal protocol allowing a user logged on to one TCP/IP host to access other host on the network. One of the remarkable feature of the Internet is the way it let’s you use the resources of a distant computer somewhere else in the world you do this with the Internet resources called Telnet. ~ follows a client server model which means you run a piece of software on your PC (client) to use the resources of a distant computer is called a host. The host allows many different clients to access its resources at the sometimes, it is no devoted to a single user.
How Telnet Works: - To use Telnet need to know the address of the host whose reassurances you want to use. you as a Telnet client contact the host using its Internet address when you contact the host the distant computer and your computer navigate that how they will communicate with each other. They decide which terminal emulation will be used.
TERMINAL EMULATION determines how your keyboard will transmit information to the distant computer and how information to the distant computer and how information will be displayed on your screen.
Server Domain: - ~ is a UNIX program that runs attended and in usually invisible to the user providing important system services. It manages all types of tasks including mail management, networking Internet services, FTP sessions and NFS (Network File Services) services.
Terminal Emulation: - The most popular ~ is VT- 100 the computer works like a dumb terminal except it is connected via a phone line instead of a direct connection. Often you will not be able to use graphical part of the Internet such as www (World Wide Web). you will be able to access text only portion of the web. This kind of Internet account is also known as “shell” account. this shell account is available with VSNL for the students of India.
