Computer Network for Class 12 CBSE Board
- 1. Presented By: Narendra Kumar PGT-CS, KV Silchar Silchar, Assam Communication and Computer Networks
- 2. What is a Network? When two or more computing devices are interconnected through transmission media for sharing of information and sharing of resources is called a computer network. •The computers can be geographically located anywhere. •Transmission media is used to transfer data from one computer to another computer.
- 3. Applications of Computer Network 1. Sharing of Resources Hardware (Computing resources, Disks, Printers) Software (application software) 2. Sharing of Information Easy accessibility from anywhere (files, databases) Search Capability (WWW) 3. Communication Medium: Email Message broadcast
- 4. Components of a Computer Network Components of Computer Network Hosts / Nodes Server & Clients Network Hardware Communication Channel Software Network Services PC, Laptops, Smartphones, Printers etc. NIC, Switch, Hub, Routers etc. Guided- Cables Unguided-Radio wave, Micro wave BNS, File Sharing, Email, DNS etc. Protocols, NOS etc.
- 5. Types of Networks On the basis of Number of Computers & devices, Complexity and Geographical spread, Networks can be classified in four types. Types of Network Local Area Network (LAN) Wide Area Network (WAN) Metropolitan Area Network (MAN) Personal Area Network (PAN)
- 6. Personal Area Network (PAN) Personal area network (PAN) is an interconnection between different devices like smartphone, tablet, computer, wearable gadgets and other digital devices with a small area range of 10 meters. Generally connect through Bluetooth, Infrared etc.
- 7. Local Area Network (LAN) A local-area network (LAN) is a computer network that spans a relatively small area Like a room, building or group of buildings within 1 KM, LAN can be connected to other LANs over any distance via telephone lines and radio waves. LAN shares a variety of resources like Hardware (e.g. printers, scanners, Hard Disk etc.), Software (e.g. application programs) and data. Usually connected through : • Ethernet • RJ45 Socket • UTP Cable • Network Interface Card • Switch/Hub/Routers • TCP/IP • Star Topology When LAN is formed using Wireless transmission media & Protocols , then it is called WLAN.
- 8. Metropolitan Area Network (MAN) A metropolitan area network (MAN) is a network with a size greater than LAN but smaller than a WAN. It normally comprises networked interconnections within a city that also offers a connection to the Internet. • Network size generally ranges from 5 to 50 km • MAN provide uplinks for connecting LANs to WANs and Internet. • Example: Cable TV
- 9. Wide Area Network (WAN) A wide area network (WAN) is a computer network that covers a large geographical area comprising a region, a country, a continent or even the whole world. WAN includes the technologies to transmit data, image, audio and video information over long distances and among different LANs and MANs. • Provides uplinks for connecting LANs and MANs to the Internet. • Communication links are provided by public carriers like telephone networks, network providers, cable systems, satellites etc. • Example: Internet
- 10. Types of Networks by Component Roles Peer to Peer (P2P): are the simplest type of networks; every computer can communicate directly with every other computer. P2P networks do not use a centralized computer known Server. P2P networks are popular as Home networks and for use in small companies due to less expensive to setup and maintain than other types of networks. But P2P are limited in scope, Not Flexible and difficult to secure.
- 11. Client Server Network: use a centralized computer known Server to facilitate communication, and resource sharing between other computers on a network, which are known as Clients. A Server is a computer on network, dedicated to processing clients requests. Servers can be Dedicated server or Non-Dedicated server A Client is a computer or a device on network that requests and utilizes network resources. Types of Networks by Component Roles
- 12. •The Server controls security of Network. •Provide User logon accounts and passwords for user of the network. •Access to multiple shared resources can be centrally granted to a single user or groups of users. •Clients are dependent on server. •Problems on the network can be tracked, diagnosed and often fixed from one location. •Optimized for faster processing time to handle many requests from clients. •Larger disk space means it is more scalable and more clients can be added as necessary. Types of Networks by Component Roles
- 13. Evolution of Networking National Science Foundation Network. Government fund was discontinued in 1995 and commercialized. Advanced Research Projects Agency NETwork (ARPANET) was first network. It was shutdown in 1990’s. Internet is a world wide network of computer networks.
- 14. How does Internet Function? Internet is referred as Network of Networks. It is a collection of small and large networks around the world, interconnected using the telephone network. The connections between the computers are a mixture of old-fashioned copper cables, fiber-optic cables, radio waves and satellite links. Basic task of Internet is to transport information from one place to another in digital form. Networks are interconnected to Internet backbone through Gateways. All computers on Internet communicate through a set of rules called protocols. Internet Protocol (IP) and Transport Control Protocol (TCP). Information/Data is transport in small parts called Packets.
- 15. Gateway & Backbone Network A Gateway is a device that connects dissimilar networks using different transmission protocols. A Backbone is central interconnecting structure that connects one or more networks just like the trunk of a tree or the spine of a human being.
- 16. The communication protocol used by internet is TCP/IP. Each protocol serves specific functions • TCP defines how applications can create channels of communication across a network. It also manages how a message is assembled into smaller packets before transmitted over the internet and reassembled in the right order at the destination address. • IP defines how to address and route each packet to make sure it reaches the right destination. Each gateway computer on the network checks this IP address to determine where to forward the message. TCP/IP (Transmission Control Protocol/Internet Protocol)
- 17. Data Communication Terminologies Data Channel-It is the medium used to carry information or data from one point to another. This data channel can be wired or wireless. Transmission channel may be analog or digital. Unit bps(Bits) Bps (Bytes) 1000 1 Kilobits per second 125 Bps 1,000,000 1,000,000 bps 125,000 Bps Gigabit per second 1,000,000,000 bps 125,000,000 Bps Baud-It is the measurement for the maximum information carrying capacity of a communication channel. It is synonymous with bps(bits per second). Data Transfer Rate- It is the amount of digital data transferred from one place to another in a given time. It is the speed of data transfer and usually measured in bits per second (bps) or bytes per second (Bps). For example, 100 KB (kilobytes) = 800 Kb (kilobits). 1 Byte= 8 Bits or 1/8 Byte
- 18. Data Communication Terminologies Bandwidth-Data transfer rates that can be supported by a network is called its bandwidth. It generally measures the amount of data that can be transferred in a given amount of time over a data channel. It’s the difference between the highest and the lowest frequencies of a data channel. The measurement unit of frequency is cycles per second i.e. hertz. It can be also measured in bits per second (bps). • Narrowband- Speed of narrowband varies between 45 to 300 Baud. • Voice-band- Speed of voice-band channels ranges up to 9600 Baud.. • Broadband- The speed of broadband channels ranges up to 1 million Baud or more. Protocol: It is a set of rules and regulations used to communicate over the network. Some commonly used protocols over network are : TCP/IP FTP HTTP SMTP IMAP POP3 VOIP
- 19. Transmission Media Networking media can be defined simply as the means by which signals (data) are transfer from one computer to another computer (either by cable or wireless means). Unguided Media Transmission Media Coaxial Twisted Fibre Optics Radio wave Microwave Infrared Unshielded Shielded Baseband Broadband Guided Media
- 20. Twisted Pair Cable: A twisted pair cable comprises of two separate insulated copper wires, which are twisted together and run in parallel. The twisting of wires reduce crosstalk, which is protection from Internal and external signal interference. Applications of Twisted-Pair Cables • In telephone lines •In DSL lines • In LANs
- 21. Twisted Pair Cable: Advantages Disadvantages • It is simple • Easy to install and maintain • Physically Flexible • It is Low weight • Easily connected • It is Inexpensive • High attenuation, it cannot carry a signal over long distances without the use of repeaters. • Low bandwidth capabilities, unsuitable for broadband applications. • Support maximum data rates 1Mbps without conditioning and 10 Mbps with conditioning There are two types of twisted pair cables − Unshielded Twisted Pair (UTP): These generally comprise of wires and insulators. UTP is available in 8 Categories i.e. CAT-1 to CAT-8. Shielded Twisted Pair (STP): These have a braided wired mesh that encases each pair of insulated wires. It has less crosstalk due to shielding.
- 22. Coaxial Cable: Coaxial cable consists of a solid wire core surrounded by one or more foil or wire shields, each separated by plastic insulators. The inner core carries the signal and the shield provides ground. The coaxial cable has high electrical properties and is suitable for high speed communication. Generally this type of cable is used in Cable Television, CCTV, Internet etc. • Better than twisted pair cable due to data transmission characteristics. • Used for as shared cable network. • Used for broadband transmission i.e. several channels can be transmitted simultaneously. • Higher bandwidth upto 400 MBPS • Expensive compared to twisted pair cables. • Not Compatible with Twisted pair.
- 23. Optical Fiber Cable: • It can be of either single node that supports a segment length of upto 2 kms and band- width of upto 100 Mbps or Multinode with a segment length of 100 kms and bandwidth of 2 Gbps. • Optical fiber is the technology associated with data transmission using light pulses traveling along with a long fiber which is usually made of plastic or glass. • Metal wires are preferred for transmission in optical fiber communication as signals travel with fewer damages. • Fiber optics is used long-distance and high-performance data networking. • The data to be transmitted is modulated onto the light beam using frequency modulation techniques. The signals can then be picked up at the receiving end and demodulated. The bandwidth of the medium is potentially very high. For LEDs, this ranges between 20 and 150 mbps and higher rates are possible using LDs.
- 24. Optical Fiber Cable: Advantages Disadvantages • Immune to electrical and magnetic interference. • Highly suitable for harsh industrial environments. • it guarantees secure transmission and has a very high transmission capacity • Can be used for broadband transmission where several channels (i.e., bands of frequency) are handled in parallel. • It is also possible to mix data transmission channels with channels for telescope, graphics, TV and sound. • Installation problem. • Connecting two fibers together is a difficult process. • Because of noise immunity, they are virtually impossible to tap. • Light can reach the receiver out of phase. • Connection losses are common problem • Difficult to solder • Most expensive of all the cables.
- 25. Guided Media Comparison Type Sub Type Max. Segment Length Bandwidth Supported Installation Cost Interference Twisted Pair Cable UTP 100 meters 100 Mbps Easy Cheapest High STP 100 meters 500 Mbps Moderate Moderate Moderate Coaxial Cable Thinnet 185 meters 10 Mbps Easy Cheap Moderate Thicknet 500 meters 10 Mbps Hard Moderate Low Fibre Optic Cable Multinode 2 kms 100 Mbps Very Hard Expensive None Singlenode 100 kms 2 Gbps Very Hard Expensive None
- 26. Unguided Media-Micro Wave • Microwaves are the electromagnetic waves which have frequency range between 1 GHz to 300 GHz • These signals are used for long distance communication and are similar to radio and television signals. These are unidirectional in nature which means that they can travel only in straight line. • A Line-of-Sight signal passes through the atmosphere, originates from a dish antenna, travels in a straight line free of material obstacles and received by another dish antenna. • The microwave transmission basically consists of a transmitter, receiver, and the atmosphere. • In case of microwave communication, parabolic antennas are mounted on towers to send a beam to the other antennas tens of kilometers away. The higher the towers means the greater the range. • With a use of tower that is 100 meter high, then distances of 100 km between the towers are feasible. The microwave transmission is line-of-sight transmission.
- 27. Unguided Media-Micro Wave •Microwave provides cheaper than digging trenches for laying cables and maintaining repeaters and cables if cables get broken by a variety of causes. •Microwave offers freedom from land acquisition rights that are required for laying, repairing the cables •Microwave offers the ease of communication over difficult terrain •Microwave have the ability to communicate over oceans • Microwave communication is an insecure communication • In Microwave, signals from a signal antenna may split up and propagate by slightly different paths to the receiving antenna. When these out-of-phase signals recombine, they interfere, reducing the signal strength. • In microwave, bandwidth allocation is extremely limited • Microwave propagation is susceptible to weather effects like rains, thunder storms etc. • The cost of design, implementation, and maintenance of microwave links is high.
- 28. Unguided Media-Radio Wave • Radio wave transmission is the transmission that uses radio frequencies. • The radio waves have frequency range from 3 KHz and 1 GHz. • These waves are easy to generate and these can travel along long distances. These waves are omni directional in nature which means that they can travel in all the directions. • These waves are usually used for AM and FM radio, television, cellular phones and wireless LAN. Advantages Disadvantages • Radio wave transmission offers mobility • Radio wave is cheaper than digging trenches for laying cables and maintaining repeaters and cables if cables get broken by a variety of causes • Radio wave offers ease of communication over difficult terrain. • Radio wave communication provides an insecure communication • Radio wave propagation is susceptible to weather effects like rains, thunder storms etc.
- 29. Unguided Media- Satellite Microwave • The satellites accept the data or signals that are transmitted from the earth station, and amplify them, and then retransmit them to another earth station. Satellite or satellite microwave communication provides voice, fax, data and video services as well as email, file transfer, www, internet applications. • In this , the earth station consists of a satellite dish that works as an antenna and communication equipment to transmit and receive the data from satellites passes overhead. This is a special case of microwave relay system. • Satellites can cover large areas of the Earth. • The heavy usage of intercontinental traffic makes the satellite commercial attractive • This is particularly useful for sparsely populated areas. • Technological limitations preventing the deployment of large, high gain antennas on the satellite platform • The high investment cost of insurance cost associated with significant probability of failure • High atmospheric losses above 30 GHz limit carrier frequencies • Over-crowding of available bandwidths due to low antenna gains
- 30. Infrared • Infrared transmission uses infrared light to send data. • Infrared light transmits data through the air and can propagate throughout a room, bouncing off surfaces, but will not penetrate the walls. • The infrared transmission is considered as a secure transmission. • The infrared transmission has become common in Personal Digital Assistants (PDAs), TV remotes, Automotive garage doors, Wireless Speakers, etc. • The laser transmission requires direct line-of-sight. • The laser transmission is unidirectional like microwave, but it has much higher speed than the microwave transmission. • The laser transmission requires the use of a laser transmitter and a photo- sensitive receiver at each end. • The laser transmission is point-to- point transmission, typically between buildings. • The laser transmission can be adversely affected by weather. Laser
- 31. Network devices Network Devices are used to connect computers and other electronic devices to form or connect different networks. • There are many devices play important role in the smooth functioning of networks. • 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, Hub, Gateway etc.
- 32. Network devices-Modem A modem is a device/peripheral that provides access to the Internet and communicate with other computers via telephone lines. As Telephone lines carry data in analog form and computer can’t understand analog data. A modem convert the digital data from your computer into analog data and vice versa. This conversion of digital data into analog data and back again is called modulation/demodulation. Modems are of Two Types: • Internal Modems • External Modems
- 33. Network devices-RJ-45 RJ45 is the acronym for Registered Jack 45. It is an 8-pin jack used by devices to physically connect to Ethernet based local area networks (LANs). The cable used for Ethernet LANs are twisted pair and have RJ45 connectors at both ends. One end is connected to Network Interface card of Computer and other end is connected to Switch/Hub/Router of network.
- 34. Network devices- Ethernet Card Ethernet was developed at Xerox PARC, DEC and Intel. It is a technology that defines protocols for establishing a LAN. The computers that are part of Ethernet, have to install a special card called Ethernet Card. • Ethernet uses bus or star topology and can support data transfer rates of upto 100 Mbps, even upto 1Gbps nowadays. • An Ethernet card contains connections for either coaxial or twisted pair or both cables. If Ethernet Card designed to connect with coaxial cable, connection is made through BNC and in case Twisted cable, RJ-45 is used.
- 35. Network devices- Hub A hub is basically a hardware, a centralized device through which every devices such as printers, computers, are connected with each other. Generally, hubs can support 8, 12, or 24 RJ-45 ports. These are often used in a star or star-wired ring topology and require specialized software for port management. Hubs can be either passive or active. • Active hubs electrically amplify the signal as it moves from one connected device to another. • Passive hubs allow the signal to pass from one computer to another without any change.
- 36. Network devices- Switch A switch is a networking device that connects other computers, networking devices, and network segments together. It is also used to segment networks into different sub-networks called subnets or LAN segments. • A switch is responsible for filtering, that is, transforming the data in a specific way and for forwarding packets (a piece of message being transmitted) between LAN segments. • 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. • Switch supports any packet protocol. • Switch is also called as multi-port bridge.
- 37. Network devices - Router A Router is a network device that is used to separate different segments in a network to improve performance and reliability. A router works like a bridge but can handle different protocols. It is a network layer hardware device that transmits data from one LAN to another. 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. There is a Operating system and a software present in the router, with the help of this router moves the data from one network to another.
- 38. Network devices - Bridge • A bridge is a network device that is used to connect two or multiple network segments or multiple LAN segments. • It establishes an intelligent connection between two local networks with the same standard but with different types of cables. • As a packet arrives at the bridge, the bridge examines the physical destination address of the packet. • The bridge then decides whether or not to let the packet cross. • Bridges have a capacity to filter the data traffic. • Network bridges filtering works based on MAC addresses. • Bridges works on data link layer or layer 2 of OSI model.
- 39. Network devices - Repeater • A repeater is basically a device that amplifies a signal being transmitted on the network. • Repeater is used in long network lines, which exceed the maximum rated distance for a single run. • Repeater can regenerate or amplify both digital and analog signal. • Repeaters can be installed along the way to ensure that data packets reach their destination. • Repeaters are of two kinds : amplifier & signal repeater. • Repeater works on layer 1 of OSI model.
- 40. Network devices – Gateway • A Gateway is a network device that connects dissimilar networks. • It establishes an intelligent connection between a local networks and external networks with completely different structure. • A gateway operates at the highest layer of network abstraction. • Gateway expands the functionality of routers by performing the data translation and protocol conversion. • A gateway is actually a node on a network that serves as an entrance to another network.
- 41. Network devices – WiFi Card • A WiFi card is either an internal or external Local Area Network adapter with a built-in wireless radio and antenna. • The most common WiFi cards used in desktop computers are PCI-Express WiFi cards made to fit the PCI-Express card slots on the motherboard. • Nowadays WiFi- USB Adapter are easily available.
- 42. Network Topologies • Topology refers to physical structure of computers or nodes or workstations and other network devices in a network. • The selection of topology for a network can not be done in isolation as it affects the choice of media and the access method used. • There are a number of factors that is used to consider in making this choice. Cost: For a network to be cost effective, one would try to minimize installation cost. Flexibility: The topology should allow for easy reconfiguration of the network. This involves moving existing nodes and adding new ones. Reliability: The topology chosen for the network can help by allowing the location of the fault to be detected and to provide some means of isolating it. Network topologies are categorized into the following basic types : Bus Star Ring
- 43. Bus or Linear Topologies • A bus topology connects each computer (node) to a single segment trunk. • A trunk is a communication line, typically coax cable, that is referred to as the bus. The signal travels from one end of the bus to the other. • A terminator is required at each end to absorb the signal so it does not reflect back across the bus. • In this, signals are broadcast to all stations. Each computer checks the address on the signal (data frame) as it passes along the bus. If the signal’s address matches that of the computer, the computer processes the signal. If the address doesn’t match, the computer takes no action and the signal travels on down the bus. Only one computer can talk on a network at a time. A media access method (protocol) called CSMA/CD is used to handle the collisions that occur when two signals are placed on the wire at the same time. • The bus topology is passive. In other words, the computers on the bus simply listen for a signal; they are not responsible for moving the signal along. A bus topology is normally implemented with coaxial cable.
- 44. Bus or Linear Topologies
- 45. Bus or Linear Topologies Advantages Disadvantages • It is easy to install because there is a requirement of only one cable. Therefore, it uses less cable and simple wiring layout. • In this, any networking or specialized devices is not required. It only requires LAN cards, t-connectors, and terminators. • Additional nodes can be connected to an existing bus network at any point along its length. More extensive additions can be achieved by adding extra segments connected by a type of signal amplifier known as repeater. • In bus topology, if at any place, a cable disconnected or disconnection form the cable, then total network stops working. Then it becomes hard to fix the problem. • In bus topology, if you want to add new computer to replace old computer. Then at that time of adding new computer to replace old computer, network stops working. • Each node on the network is directly connected to the central bus. This means that some way of deciding who can use the network at any given time must be performed in each node.
- 46. Star Topologies •All of the stations in a star topology are connected to a central unit called a MAU (Hub, Switch etc.). •The MAU offers a common connection for all stations on the network. Each station has its own direct cable connection to the hub. In most cases, this means more cable is required than for a bus topology. However, this makes adding or moving computers a relatively easy task; simply plug them into a cable outlet on the wall. •If a cable is cut, it only affects the computer that was attached to it. This eliminates the single point of failure problem associated with the bus topology. (Unless, of course, the hub itself goes down.) •Star topologies are normally implemented using twisted pair cable, specifically unshielded twisted pair (UTP). The star topology is probably the most common form of network topology currently in use.
- 47. Star Topologies Advantages •New workstation or node can be easily added without effecting network •If there is a failure of a cable at one place, then only that cable user or computer user can get effect. •Easy to troubleshoot & error detection. Disadvantages • Every computer is connected through a individual cable to centralized device, so more cable required. • If there is a failure of centralized device, can lead to network failure.
- 48. Ring Topologies •In Ring topology, devices are connected together in circular form. •In Ring topology, each node is connected to two and only two neighboring nodes. •Data is accepted from one of the neighboring nodes and then is transmitted onwards to another. Therefore, data travels in one direction only, from node to node around the ring. After passing through each node, it returns to the sending node, which removes it. •Each station repeats or boosts the signal before passing it on to the next station. •This topology used by below technologies. •FDDI, •SONET •Token Ring
- 49. Ring Topologies Advantages • The Ring topology requires short cable length • Growth of system has minimal impact on performance • All stations have equal access. • Ring topology is suitable for optical fibers or Disadvantages • A node failure causes network failure. • It is difficult to diagnose faults. • It is not possible to shut down a small section of the ring while keeping the majority of it working normally. Network reconfiguration is difficult
- 50. Tree Topologies • The tree topology is a variation of the bus topology, the shape of the network is that of an inverted tree with the central root branching and sub-branching to the extremities of the network. • Tree topology is basically the mixture of many Star topology designs connected together using bus topology. • The tree topology is best suited for applications which have a hierarchical flow of data and control. • Tree topology is very dynamic in nature and it holds potential of expandability of networks far better than other topologies like Bus and Star.
- 51. Network Communication Protocols •Protocol:- It is a set of rules and regulations used to communicate over the network, the rules that are applicable for a network. •Protocol defines standardized formats for data packets, techniques for detecting and correcting errors and so on. •It is a formal description of message formats and the rules that two or more machines must follow to exchange those messages. •Below are some important and common protocols. •HTTP (Hypertext Transfer Protocol) •FTP (File Transfer Protocol) •TCP/IP (Transmission Control Protocol/Internet Protocol) •SLIP/PPP (Serial Line Internet Protocol/Point to Point Protocols)
- 52. TCP/IP (Transmission Control Protocol/Internet Protocol) • TCP stands for Transmission Control Protocol and IP stands for Internet Protocol. • TCP/IP is a layered protocol and set of 04 layers. • TCP/IP is the base communication protocol of the Internet. • TCP part of TCP/IP provides reliable delivery of messages between networked computers and defines how applications can create channels of communication across a network. It also manages how a message is assembled into smaller packets before transmitted over the internet and reassembled in the right order at the destination address. • IP part of TCP/IP uses numeric IP addresses to join network segments and defines how to address and route each packet to make sure it reaches the right destination. Each gateway computer on the network checks this IP address to determine where to forward the message.
- 53. TCP/IP (Transmission Control Protocol/Internet Protocol)
- 54. Hypertext Transfer Protocol (HTTP) • Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information systems. Its use for retrieving inter-linked resources, called hypertext documents, led to the establishment of the World Wide Web in 1990 by English physicist Tim Berners-Lee. • HTTP is the set of rules for transferring hypertext such as text, graphics, image, sound, video etc. on WWW (World Wide Web). • HTTP is also used as a generic protocol for communication between user agents and proxies/gateways to other Internet protocols such as SMTP, NNTP, FTP, Gopher, and WAIS.
- 55. File Transfer Protocol (FTP) •File Transfer Protocol (FTP) is a standard network protocol used to exchange and manipulate files over a TCP/IP based network, such as the Internet. •FTP is built on a client-server architecture and utilizes separate control and data connections between the client and server applications. •FTP is one of the original services on the Internet that was designed to allow for transferring files from one system to another. • FTP is very useful to transfer files from one network in an organization to another.
- 56. SLIP / PPP •SLIP/PPP (Serial line internet Protocol/Point to Point Protocol) •SLIP stands for Serial Line Internet Protocol. •SLIP is used for delivering IP packets over dial-up lines. •It defines an encapsulation mechanism. •SLIP has been largely superseded by PPP. •PPP is the Internet Standard for transmission of IP packets over serial lines. •The Point-to-Point Protocol (PPP) is currently the best solution for dial-up Internet connections including ISDN. •The IPCP (IP Control Protocol) permits the transport of IP packets over a PPP link. •PPP supports both synchronised and unsynchronised lines.
- 57. Simple Mail Transfer Protocol (SMTP) •SMTP is a set of communication guidelines that allow software to transmit an electronic mail over the internet is called Simple Mail Transfer Protocol. •SMTP is a push protocol and is used to send the mail whereas POP (post office protocol) or IMAP (internet message access protocol) are used to retrieve those mails at the receiver’s side. •SMTP is an application layer protocol. •The client who wants to send the mail opens a TCP connection to the SMTP server and then sends the mail across the connection. •The SMTP server is always on listening mode. As soon as it listens for a TCP connection from any client, the SMTP process initiates a connection on that port (25).
- 58. Post Office Protocol v3 •It provides mechanisms for storing messages sent to each user and received by SMTP in a receptacle called a mailbox. A POP3 server stores messages for each user until the user connects to download and read them using a POP3 client. •To retrieve a message from a POP3 server, a POP3 client establishes a Transmission Control Protocol (TCP) session using TCP port 110, identifies itself to the server, and then issues a series of POP3 commands: •After a POP3 client reads a message in its mailbox on a POP3 server, the message is deleted. Primarily because of this, POP3 is being supplanted by Internet Mail Access Protocol v4 (IMAP4), which offers better support for mobile users.
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