Category: communication Technologies

Email Protocols Email is one of the most popular uses of Internet world wide. As per a 2015 study, there are 2.6 billion email users worldwide who send some 205 billion email messages per day. With email accounting for so much traffic on the Internet, email protocols need to be very robust. Here we discuss some of the most popular email protocols used worldwide. SMTP SMTP stands for Simple Mail Transfer Protocol. It is connection oriented application layer protocol that is widely used to send and receive email messages. It was introduced in 1982 by RFC 821 and last updated in 2008 by RFC 5321. The updated version is most widely used email protocol. Mail servers and mail transfer agents use SMTP to both send and receive messages. However, user level applications use it only for sending messages. For retrieving they use IMAP or POP3 because they provide mail box management RFC or Request for Comments is a peer reviewed document jointly published by Internet Engineering Task Force and the Internet Society. It is written by researchers and computer scientists describing how the Internet should work and protocols and systems supporting them. POP3 POP3 or Post Office Protocol Version 3 is an application layer protocol used by email clients to retrieve email messages from mail servers over TCP/IP network. POP was designed to move the messages from server to local disk but version 3 has the option of leaving a copy on the server POP3 is a very simple protocol to implement but that limits its usage. For example, POP3 supports only one mail server for each mailbox. It has now has been made obsolete by modern protocols like IMAP. IMAP IMAP stands for Internet Message Access Protocol. IMAP was defined by RFC 3501 to enable email clients to retrieve email messages from mail servers over a TCP/IP connection. IMAP is designed to retrieve messages from multiple mail servers and consolidate them all in the user’s mailbox. A typical example is a corporate client handling multiple corporate accounts through a local mailbox located on her system. All modern email clients and servers like Gmail, Outlook and Yahoo Mail support IMAP or POP3 protocol. These are some advantages that IMAP offers over POP3 − Faster response time than POP3 Multiple mail clients connected to a single mailbox simultaneously Keep track of message state like read, deleted, starred, replied, etc. Search for messages on the server Learning working make money

Network Topologies The way in which devices are interconnected to form a network is called network topology. Some of the factors that affect choice of topology for a network are − Cost − Installation cost is a very important factor in overall cost of setting up an infrastructure. So cable lengths, distance between nodes, location of servers, etc. have to be considered when designing a network. Flexibility − Topology of a network should be flexible enough to allow reconfiguration of office set up, addition of new nodes and relocation of existing nodes. Reliability − Network should be designed in such a way that it has minimum down time. Failure of one node or a segment of cabling should not render the whole network useless. Scalability − Network topology should be scalable, i.e. it can accommodate load of new devices and nodes without perceptible drop in performance. Ease of installation − Network should be easy to install in terms of hardware, software and technical personnel requirements. Ease of maintenance − Troubleshooting and maintenance of network should be easy. Bus Topology Data network with bus topology has a linear transmission cable, usually coaxial, to which many network devices and workstations are attached along the length. Server is at one end of the bus. When a workstation has to send data, it transmits packets with destination address in its header along the bus. The data travels in both the directions along the bus. When the destination terminal sees the data, it copies it to the local disk. Advantages of Bus Topology These are the advantages of using bus topology − Easy to install and maintain Can be extended easily Very reliable because of single transmission line Disadvantages of Bus Topology These are some disadvantages of using bus topology − Troubleshooting is difficult as there is no single point of control One faulty node can bring the whole network down Dumb terminals cannot be connected to the bus Ring Topology In ring topology each terminal is connected to exactly two nodes, giving the network a circular shape. Data travels in only one pre-determined direction. When a terminal has to send data, it transmits it to the neighboring node which transmits it to the next one. Before further transmission data may be amplified. In this way, data raverses the network and reaches the destination node, which removes it from the network. If the data reaches the sender, it removes the data and resends it later. Advantages of Ring Topology These are the advantages of using ring topology − Small cable segments are needed to connect two nodes Ideal for optical fibres as data travels in only one direction Very high transmission speeds possible Disadvantages of Ring Topology These are some the disadvantages of using ring topology − Failure of single node brings down the whole network Troubleshooting is difficult as many nodes may have to be inspected before faulty one is identified Difficult to remove one or more nodes while keeping the rest of the network intact Star Topology In star topology, server is connected to each node individually. Server is also called the central node. Any exchange of data between two nodes must take place through the server. It is the most popular topology for information and voice networks as central node can process data received from source node before sending it to the destination node. Advantages of Star Topology These are the advantages of using star topology − Failure of one node does not affect the network Troubleshooting is easy as faulty node can be detected from central node immediately Simple access protocols required as one of the communicating nodes is always the central node Disadvantages of Star Topology These are the disadvantages of using star topology − Long cables may be required to connect each node to the server Failure of central node brings down the whole network Tree Topology Tree topology has a group of star networks connected to a linear bus backbone cable. It incorporates features of both star and bus topologies. Tree topology is also called hierarchical topology. Advantages of Tree Topology These are some of the advantages of using tree topology − Existing network can be easily expanded Point-to-point wiring for individual segments means easier installation and maintenance Well suited for temporary networks Disadvantages of Tree Topology These are some of the disadvantages of using tree topology − Technical expertise required to configure and wire tree topology Failure of backbone cable brings down entire network Insecure network Maintenance difficult for large networks Learning working make money

Discuss Communication Technologies Exchange of information through the use of speech, signs or symbols is called communication. When early humans started speaking, some 5,00,000 years ago, that was the first mode of communication. Communication over a long distance when people who are communicating are not in direct line of each other’s site is called telecommunication. Invention of telephone and establishment of commercial telephony in 1878 marked a turnaround in communication systems and real telecommunication was born. Telephones slowly gave way to television, videophone, satellite and finally computer networks. Computer networks have revolutionized modern day communication and communication technologies. In this tutorial, we will discuss in detail how networks have evolved since the first network known as ARPANET. We will also discuss the hardware and software components of networking and the concept of global communication via Internet. Learning working make money

Communication Technologies – Hacking Unauthorized access to data in a device, system or network is called hacking. A person hacking another person’s system is called hacker. A hacker is a highly accomplished computer expert who can exploit the smallest of vulnerabilities in your system or network to hack it. A hacker may hack due to any of the following reasons − Steal sensitive data Take control of a website or network Test potential security threats Just for fun Broadcast personal views to a large audience Types of Hacking Depending on the application or system being broken into, these are some categories of hacking common in the cyber world − Website hacking Network hacking Email hacking Password hacking Online banking hacking Ethical Hacking As iron sharpens iron, hacking counters hacking. Using hacking techniques to identify potential threats to a system or network is called ethical hacking. For a hacking activity to be termed ethical, it must adhere to these criteria − Hacker must have written permission to identify potential security threats Individual’s or company’s privacy must be maintained Possible security breaches discovered must be intimated to the concerned authorities At a later date, no one should be able to exploit ethical hacker’s inroads into the network Cracking A term that goes hand in glove with hacking is cracking. Gaining unauthorized access to a system or network with malicious intent is called cracking. Cracking is a crime and it may have devastating impact on its victims. Crackers are criminals and strong cyber laws have been put into place to tackle them. Learning working make money

Communication Technologies – Quick Guide Communication Technologies – Introduction Exchange of information through the use of speech, signs or symbols is called communication. When early humans started speaking, some 5,00,000 years ago, that was the first mode of communication. Before we dive into modern technologies that drive communication in contemporary world, we need to know how humans developed better communication techniques to share knowledge with each other. History of Communication Communicating with people over a distance is known as telecommunication. The first forms of telecommunication were smoke signals, drums or fire torches. The major disadvantage with these communication systems was that only a set of pre-determined messages could be transmitted. This was overcome in the 18th and 19th century through development of telegraphy and Morse code. Invention of telephone and establishment of commercial telephony in 1878 marked a turnaround in communication systems and real telecommunication was born. International Telecommunication Union (ITU) defines telecommunication as transmission, emission and reception of any signs, signals or messages by electromagnetic systems. Now we had the communication technology to connect with people physically located thousands of kilometers away. Telephones slowly gave way to television, videophone, satellite and finally computer networks. Computer networks have revolutionized modern day communication and communication technologies. That will be the subject of our in-depth study in subsequent chapters. History Of Networking ARPANET – the First Network ARPANET − Advanced Research Projects Agency Network − the granddad of Internet was a network established by the US Department of Defense (DOD). The work for establishing the network started in the early 1960s and DOD sponsored major research work, which resulted in development on initial protocols, languages and frameworks for network communication. It had four nodes at University of California at Los Angeles (UCLA), Stanford Research Institute (SRI), University of California at Santa Barbara (UCSB) and University of Utah. On October 29, 1969, the first message was exchanged between UCLA and SRI. E-mail was created by Roy Tomlinson in 1972 at Bolt Beranek and Newman, Inc. (BBN) after UCLA was connected to BBN. Internet ARPANET expanded to connect DOD with those universities of the US that were carrying out defense-related research. It covered most of the major universities across the country. The concept of networking got a boost when University College of London (UK) and Royal Radar Network (Norway) connected to the ARPANET and a network of networks was formed. The term Internet was coined by Vinton Cerf, Yogen Dalal and Carl Sunshine of Stanford University to describe this network of networks. Together they also developed protocols to facilitate information exchange over the Internet. Transmission Control Protocol (TCP) still forms the backbone of networking. Telenet Telenet was the first commercial adaptation of ARPANET introduced in 1974. With this the concept of Internet Service Provider (ISP) was also introduced. The main function of an ISP is to provide uninterrupted Internet connection to its customers at affordable rates. World Wide Web With commercialization of internet, more and more networks were developed in different part of the world. Each network used different protocols for communicating over the network. This prevented different networks from connecting together seamlessly. In the 1980s, Tim Berners-Lee led a group of Computer scientists at CERN, Switzerland, to create a seamless network of varied networks, called the World Wide Web (WWW). World Wide Web is a complex web of websites and web pages connected together through hypertexts. Hypertext is a word or group of words linking to another web page of the same or different website. When the hypertext is clicked, another web page opens. The evolution from ARPANET to WWW was possible due to many new achievements by researchers and computer scientists all over the world. Here are some of those developments − Year Milestone 1957 Advanced Research Project Agency formed by US 1969 ARPANET became functional 1970 ARPANET connected to BBNs 1972 Roy Tomlinson develops network messaging or E-mail. Symbol @ comes to mean “at” 1973 APRANET connected to Royal Radar Network of Norway 1974 Term Internet coined First commercial use of ARPANET, Telenet, is approved 1982 TCP/IP introduced as standard protocol on ARPANET 1983 Domain Name System introduced 1986 National Science Foundation brings connectivity to more people with its NSFNET program 1990 ARPANET decommissioned First web browser Nexus developed HTML developed 2002-2004 Web 2.0 is born Communication Technologies – Terminologies Before we dive into details of networking, let us discuss some common terms associated with data communication. Channel Physical medium like cables over which information is exchanged is called channel. Transmission channel may be analog or digital. As the name suggests, analog channels transmit data using analog signals while digital channels transmit data using digital signals. In popular network terminology, path over which data is sent or received is called data channel. This data channel may be a tangible medium like copper wire cables or broadcast medium like radio waves. Data Transfer Rate The speed of data transferred or received over transmission channel, measured per unit time, is called data transfer rate. The smallest unit of measurement is bits per second (bps). 1 bps means 1 bit (0 or 1) of data is transferred in 1 second. Here are some commonly used data transfer rates − 1 Bps = 1 Byte per second = 8 bits per second 1 kbps = 1 kilobit per second = 1024 bits per second 1 Mbps = 1 Megabit per second = 1024 Kbps 1 Gbps = 1 Gigabit per second = 1024 Mbps Bandwidth Data transfer rates that can be supported by a network is called its bandwidth. It is measured in bits per second (bps). Modern day networks provide bandwidth in Kbps, Mbps and Gbps. Some of the factors affecting a network’s bandwidth include − Network devices used Protocols used Number of users connected Network overheads like collision, errors, etc. Throughput Throughput is the actual speed with which data gets transferred over the network. Besides transmitting the actual data, network bandwidth is used for transmitting error messages, acknowledgement frames, etc. Throughput is

Network Devices Hardware devices that are used to connect computers, printers, fax machines and other electronic devices to a network are called network devices. These devices transfer data in a fast, secure and correct way over same or different networks. Network devices may be inter-network or intra-network. Some devices are installed on the device, like NIC card or RJ45 connector, whereas some are part of the network, like router, switch, etc. Let us explore some of these devices in greater detail. Modem Modem is a device that enables a computer to send or receive data over telephone or cable lines. The data stored on the computer is digital whereas a telephone line or cable wire can transmit only analog data. The main function of the modem is to convert digital signal into analog and vice versa. Modem is a combination of two devices − modulator and demodulator. The modulator converts digital data into analog data when the data is being sent by the computer. The demodulator converts analog data signals into digital data when it is being received by the computer. Types of Modem Modem can be categorized in several ways like direction in which it can transmit data, type of connection to the transmission line, transmission mode, etc. Depending on direction of data transmission, modem can be of these types − Simplex − A simplex modem can transfer data in only one direction, from digital device to network (modulator) or network to digital device (demodulator). Half duplex − A half-duplex modem has the capacity to transfer data in both the directions but only one at a time. Full duplex − A full duplex modem can transmit data in both the directions simultaneously. RJ45 Connector RJ45 is the acronym for Registered Jack 45. RJ45 connector is an 8-pin jack used by devices to physically connect to Ethernet based local area networks (LANs). Ethernet is a technology that defines protocols for establishing a LAN. The cable used for Ethernet LANs are twisted pair ones and have RJ45 connector pins at both ends. These pins go into the corresponding socket on devices and connect the device to the network. Ethernet Card Ethernet card, also known as network interface card (NIC), is a hardware component used by computers to connect to Ethernet LAN and communicate with other devices on the LAN. The earliest Ethernet cards were external to the system and needed to be installed manually. In modern computer systems, it is an internal hardware component. The NIC has RJ45 socket where network cable is physically plugged in. Ethernet card speeds may vary depending upon the protocols it supports. Old Ethernet cards had maximum speed of 10 Mbps. However, modern cards support fast Ethernets up to a speed of 100 Mbps. Some cards even have capacity of 1 Gbps. Router A router is a network layer hardware device that transmits data from one LAN to another if both networks support the same set of protocols. So a router is typically connected to at least two LANs and the internet service provider (ISP). It receives its data in the form of packets, which are data frames with their destination address added. Router also strengthens the signals before transmitting them. That is why it is also called repeater. Routing Table A router reads its routing table to decide the best available route the packet can take to reach its destination quickly and accurately. The routing table may be of these two types − Static − In a static routing table the routes are fed manually. So it is suitable only for very small networks that have maximum two to three routers. Dynamic − In a dynamic routing table, the router communicates with other routers through protocols to determine which routes are free. This is suited for larger networks where manual feeding may not be feasible due to large number of routers. Switch Switch is a network device that connects other devices to Ethernet networks through twisted pair cables. It uses packet switching technique to receive, store and forward data packets on the network. The switch maintains a list of network addresses of all the devices connected to it. On receiving a packet, it checks the destination address and transmits the packet to the correct port. Before forwarding, the packets are checked for collision and other network errors. The data is transmitted in full duplex mode Data transmission speed in switches can be double that of other network devices like hubs used for networking. This is because switch shares its maximum speed with all the devices connected to it. This helps in maintaining network speed even during high traffic. In fact, higher data speeds are achieved on networks through use of multiple switches. Gateway Gateway is a network device used to connect two or more dissimilar networks. In networking parlance, networks that use different protocols are dissimilar networks. A gateway usually is a computer with multiple NICs connected to different networks. A gateway can also be configured completely using software. As networks connect to a different network through gateways, these gateways are usually hosts or end points of the network. Gateway uses packet switching technique to transmit data from one network to another. In this way it is similar to a router, the only difference being router can transmit data only over networks that use same protocols. Wi-Fi Card Wi-Fi is the acronym for wireless fidelity. Wi-Fi technology is used to achieve wireless connection to any network. Wi-Fi card is a card used to connect any device to the local network wirelessly. The physical area of the network which provides internet access through Wi-Fi is called Wi-Fi hotspot. Hotspots can be set up at home, office or any public space. Hotspots themselves are connected to the network through wires. A Wi-Fi card is used to add capabilities like teleconferencing, downloading digital camera images, video chat, etc. to old devices. Modern devices come with their in-built wireless network adapter. Learning working make money

Communication Technologies – Firewall There exist multiple approaches to counter or at least reduce security threats. Some of these are − Authenticating users accessing a service Providing access to authorized users Using encrypted passwords for remote log on Using biometric authorization parameters Restricting traffic to and from Firewalls are the first line of defense against unauthorized access to private networks. They can be used effectively against virus, Trojan or worm attacks. How Firewalls Work Dictionary defines firewall as a wall or partition designed to inhibit or prevent spread of fire. In networks, a system designed to protect an intranet from unauthorized access is called firewall. A private network created using World Wide Web software is called an intranet. Firewall may be implemented in both hardware and software. All traffic to and from the network is routed through the firewall. The firewall examines each message and blocks those that does not meet the pre-defined security criteria. These are some of the prevalent techniques used by firewalls − Packet level filtering − Here each packet is examined depending on user-defined rules. It is very effective and transparent to users, but difficult to configure. Also, as IP address is used to identify users, IP spoofing by malicious parties can prove counterproductive. Circuit level filtering − Like good old telephone connections, circuit level filtering applies security mechanisms while connection between two systems is being established. Once the connection is deemed secure, data transmission can take place for that session. Application level filtering − Here, security mechanisms are applied to commonly used applications like Telnet, FTP servers, storage servers, etc. This is very effective but slows down performance of the applications. Proxy server − As the name suggests, proxy server is used to interrupt all incoming and outgoing messages and mask the true server address. A firewall may use a combination of two or more techniques to secure the network, depending on extent of security required. Learning working make money

Security Acts And Laws Cyber Crimes Any unlawful activity involving or related to computer and networks is called cybercrime. Dr. K. Jaishankar, Professor and Head of the Department of Criminology, Raksha Shakti University, and Dr. Debarati Halder, lawyer and legal researcher, define cybercrime thus − Offences that are committed against individuals or groups of individuals with a criminal motive to intentionally harm the reputation of the victim or cause physical or mental harm, or loss, to the victim directly or indirectly, using modern telecommunication networks such as Internet (networks including but not limited to Chat rooms, emails, notice boards and groups) and mobile phones (Bluetooth/SMS/MMS). This definition implies that any crime perpetrated on the Internet or using computers is a cybercrime. Examples of cybercrimes include − Cracking Identity theft Hate crime E-commerce fraud Credit card account theft Publishing obscene content Child pornography Online stalking Copyright infringement Mass surveillance Cyber terrorism Cyber warfare Cyber Law Cyber law is a term that encompasses legal issues related to use of Internet and cyberspace. It is a broad term that covers varied issues like freedom of expression, internet usage, online privacy, child abuse, etc. Most of the countries have one or the other form of cyber law in place to tackle the growing menace of cybercrimes. A major issue here is that in any crime perpetrator, victim and instruments used might be spread across multiple locations nationally as well as internationally. So investigating the crime needs close collaboration between computer experts and multiple government authorities, sometimes in more than one country. Indian IT Act Information Technology Act, 2000 is the primary Indian law dealing with cybercrime and e-commerce. The law, also called ITA-2000 or IT Act, was notified on 17th October 2000 and is based on the United Nations Model Law on Electronic Commerce 1996 recommended by the UN General Assembly on 30th January 1997. The IT Act covers whole of India and recognizes electronic records and digital signatures. Some of its prominent features include − Formation of Controller of Certifying Authorities to regulate issuance of digital signatures Establishment of Cyber Appellate Tribunal to resolve disputes due to the new law Amendment in sections of Indian Penal Code, Indian Evidence Act, Banker’s Book Evidence Act and RBI Act to make them technology compliant The IT Act was framed to originally to provide legal infrastructure for e-commerce in India. However, major amendments were made in 2008 to address issues like cyber terrorism, data protection, child pornography, stalking, etc. It also gave authorities the power to intercept, monitor or decrypt any information through computer resources. IPR Issues IPR stands for Intellectual Property Rights. IPR is legal protection provided to creators of Intellectual Property (IP). IP is any creation of the intellect or mind, like art, music, literature, inventions, logo, symbols, tag lines, etc. Protecting the rights of intellectual property creators is essentially a moral issue. However, law of the land does provide legal protection in case of violation of these rights. Intellectual Property Rights include − Patents Copyrights Industrial design rights Trademarks Plant variety rights Trade dress Geographical indications Trade secrets Violation of Intellectual Property Rights is called infringement in case of patents, copyrights and trademarks, and misappropriation in case of trade secrets. Any published material that you view or read on the Internet is copyright of its creator and hence protected by IPR. You are legally and morally obliged not to use it and pass it off as your own. That would be infringement of creator’s copyright and you may incur legal action. Learning working make money

Communication Technologies – VoIP VoIP is the acronym for Voice over Internet Protocol. It means telephone services over Internet. Traditionally Internet had been used for exchanging messages but due to advancement in technology, its service quality has increased manifold. It is now possible to deliver voice communication over IP networks by converting voce data into packets. VoIP is a set of protocols and systems developed to provide this service seamlessly. Here are some of the protocols used for VoIP − H.323 Session Initiation Protocol (SIP) Session Description Protocol (SDP) Media Gateway Control Protocol (MGCP) Real-time Transport Protocol (RTP) Skype Protocol We will discuss two of the most fundamental protocols – H.323 and SIP – here. H.323 H.323 is a VoIP standard for defining the components, protocols and procedures to provide real-time multimedia sessions including audio, video and data transmissions over packetswitched networks. Some of the services facilitated by H.323 include − IP telephony Video telephony Simultaneous audio, video and data communications SIP SIP is an acronym for Session Initiation Protocol. SIP is a protocol to establish, modify and terminate multimedia sessions like IP telephony. All systems that need multimedia sessions are registered and provided SIP address, much like IP address. Using this address, caller can check callee’s availability and invite it for a VoIP session accordingly. SIP facilitates multiparty multimedia sessions like video conferencing involving three or more people. In a short span of time SIP has become integral to VoIP and largely replaced H.323. Learning working make money

Communication Technologies – Cookies Cookies are small text files with their unique ID stored on your system by a website. The website stores your browsing details like preferences, customizations, login ID, pages clicked, etc. specific to that website. Storing this information enables the website to provide you with a customized experience the next time you visit it. How Cookies Work When you visit a website through your browser, the website creates and stores a cookie file in your browser or program data folder/sub-folder. This cookie may be of two types − Session cookie − It is valid only till the session lasts. Once you exit the website the cookie is automatically deleted. Persistent cookie It is valid beyond your current session. Its expiration date is mentioned within the cookie itself. A cookie stores these information − Name of website server Cookie expiration date/time Unique ID A cookie is meaningless by itself. It can be read only by the server that stored it. When you visit the website subsequently, its server matches cookie ID with its own database of cookies and loads webpages according to your browsing history. Handling Cookies Cookies were initially designed to enhance user’s web browsing experience. However, in the current aggressive marketing scenario, rogue cookies are being used to create your profile based on your browsing patterns without consent. So you need to be wary of cookies if you care about your privacy and security. Almost all modern-day browsers give you options to allow, disallow or limit cookies on your system. You can view the cookies active on your computer and make decisions accordingly. Learning working make money