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Protocols and standards

This document discusses various networking protocols and network connection types. It begins by defining protocols and their role in governing network communication. It then describes common protocols like TCP, IP, UDP, HTTP and others. It explains the differences between connection-oriented protocols like TCP that establish connections, and connectionless protocols like UDP that do not. Finally, it discusses common network devices like hubs, switches, routers, and their functions.

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Protocols and Standards, Connection-Oriented and Connectionless Service Priyanka M Assistant Professor Department of computer science Amrita school of arts and sciences
Protocol  Protocols define format, order of messages sent and received among the network entities, and action taken on message transmission, receipt.  Human Protocols  What’s the time?  I have a question?  Introduction  Network Protocols  Communicate among Machines rather than humans  All Communication activity in internet is governed by protocols  For instants:  Specific messages sent  Specific actions taken when messages received, or the other events
Protocols
Types of Protocols  Transmission Control Protocol (TCP): TCP is a popular communication protocol which is used for communicating over a network. It divides any message into series of packets that are sent from source to destination and there it gets reassembled at the destination.  Internet Protocol (IP): IP is designed explicitly as addressing protocol. It is mostly used with TCP. The IP addresses in packets help in routing them through different nodes in a network until it reaches the destination system. TCP/IP is the most popular protocol connecting the networks.  User Datagram Protocol (UDP): UDP is a substitute communication protocol to Transmission Control Protocol implemented primarily for creating loss-tolerating and low-latency linking between different applications.  Post office Protocol (POP): POP3 is designed for receiving incoming E-mails.
Types of Protocols  Simple mail transport Protocol (SMTP): SMTP is designed to send and distribute outgoing E-Mail.  File Transfer Protocol (FTP): FTP allows users to transfer files from one machine to another. Types of files may include program files, multimedia files, text files, and documents, etc.  Hyper Text Transfer Protocol (HTTP): HTTP is designed for transferring a hypertext among two or more systems. HTML tags are used for creating links. These links may be in any form like text or images. HTTP is designed on Client-server principles which allow a client system for establishing a connection with the server machine for making a request. The server acknowledges the request initiated by the client and responds accordingly.
Types of Protocols  Hyper Text Transfer Protocol Secure (HTTPS): It is a standard protocol to secure the communication among two computers one using the browser and other fetching data from web server. HTTP is used for transferring data between the client browser (request) and the web server (response) in the hypertext format, same in case of HTTPS except that the transferring of data is done in an encrypted format. So it can be said that https thwart hackers from interpretation or modification of data throughout the transfer of packets.  Telnet: Telnet is a set of rules designed for connecting one system with another. The connecting process here is termed as remote login. The system which requests for connection is the local computer, and the system which accepts the connection is the remote computer.  Gopher: Gopher is a collection of rules implemented for searching, retrieving as well as displaying documents from isolated sites. Gopher also works on the client/server principle.
Connection-Oriented Service  A connection-oriented service is a network service that was designed and developed after the telephone system.  A connection-oriented service is used to create an end-to-end connection between the sender and the receiver before transmitting the data over the same or different networks.  In connection-oriented service, packets are transmitted to the receiver in the same order the sender has sent them.  It uses a handshake method that creates a connection between the user and sender for transmitting the data over the network.  Hence it is also known as a reliable network service.
Connection-Oriented Service Suppose, a sender wants to send data to the receiver. Then, first, the sender sends a request packet to a receiver in the form of an SYN packet. After that, the receiver responds to the sender's request with an (SYN-ACK) signal/packets. That represents the confirmation is received by the receiver to start the communication between the sender and the receiver. Now a sender can send the message or data to the receiver. Similarly, a receiver can respond or send the data to the sender in the form of packets. After successfully exchanging or transmitting data, a sender can terminate the connection by sending a signal to the receiver. In this way, we can say that it is a reliable network service.
Connectionless Service  A connection is similar to a postal system, in which each letter takes along different route paths from the source to the destination address.  Connectionless service is used in the network system to transfer data from one end to another end without creating any connection.  So it does not require establishing a connection before sending the data from the sender to the receiver.  It is not a reliable network service because it does not guarantee the transfer of data packets to the receiver, and data packets can be received in any order to the receiver.  Therefore we can say that the data packet does not follow a defined path.  In connectionless service, the transmitted data packet is not received by the receiver due to network congestion, and the data may be lost.
Connectionless Service For example, a sender can directly send any data to the receiver without establishing any connection because it is a connectionless service. Data sent by the sender will be in the packet or data streams containing the receiver's address. In connectionless service, the data can be travelled and received in any order. However, it does not guarantee to transfer of the packets to the right destination.
Protocols used  What is a TCP? TCP (Transmission Control Protocol) is a connection-oriented protocol that allows communication between two or more computer devices by establishing connections in the same or different networks. It is the most important protocol that uses internet protocol to transfer the data from one end to another. Hence, it is sometimes referred to as TCP/IP. It ensures that the connection is established and maintained until the data packet is transferring between the sender and receiver is complete  What is UDP? The UDP (User Datagram Protocol) is a connectionless protocol that allows communication between two or more devices without establishing any connection. In this protocol, a sender sends the data packets to the receiver that holds the destination address. A UDP does not ensure to deliver the data packets to the correct destination, and it does not generate any acknowledgment about the sender's data. Similarly, it does not acknowledge the receiver about the data. Hence, it is an unreliable protocol.
Connection-Oriented vs Connectionless Service
Connection-Oriented vs Connectionless Service
Network Devices
Repeater  A repeater operates at the physical layer.  Its job is to regenerate the signal over the same network before the signal becomes too weak or corrupted so as to extend the length to which the signal can be transmitted over the same network.  It is that they do not amplify the signal. When the signal becomes weak, they copy the signal bit by bit and regenerate it at the original strength.  It is a 2 port device.  They are also known as signal boosters.
Hub  A hub is basically a multiport repeater.  A hub connects multiple wires coming from different branches, for example, the connector in star topology which connects different stations.  Hubs cannot filter data, so data packets are sent to all connected devices.  In other words, collision domain of all hosts connected through Hub remains one.  Also, they do not have the intelligence to find out best path for data packets which leads to inefficiencies and wastage.
Types of Hub  Active Hub:- These are the hubs which have their own power supply and can clean, boost, and relay the signal along with the network. It serves both as a repeater as well as wiring center. These are used to extend the maximum distance between nodes.  Passive Hub :- These are the hubs which collect wiring from nodes and power supply from active hub. These hubs relay signals onto the network without cleaning and boosting them and can’t be used to extend the distance between nodes.  Intelligent Hub :- It work like active hubs and include remote management capabilities. They also provide flexible data rates to network devices. It also enables an administrator to monitor the traffic passing through the hub and to configure each port in the hub.
Bridge  A bridge operates at data link layer.  A bridge is a repeater, with add on the functionality of filtering content by reading the MAC addresses of source and destination.  It is also used for interconnecting two LANs working on the same protocol.  It has a single input and single output port, thus making it a 2 port device.
Types of Bridges  Transparent Bridges:- These are the bridge in which the stations are completely unaware of the bridge’s existence i.e. whether or not a bridge is added or deleted from the network, reconfiguration of the stations is unnecessary. These bridges make use of two processes i.e. bridge forwarding and bridge learning.  Source Routing Bridges:- In these bridges, routing operation is performed by source station and the frame specifies which route to follow. The host can discover frame by sending a special frame called discovery frame, which spreads through the entire network using all possible paths to destination.
Switch  A switch is a multiport bridge with a buffer and a design that can boost its efficiency(a large number of ports imply less traffic) and performance.  A switch is a data link layer device.  The switch can perform error checking before forwarding data, that makes it very efficient as it does not forward packets that have errors and forward good packets selectively to correct port only.  In other words, switch divides collision domain of hosts, but broadcast domain remains same.
Routers  A router is a device like a switch that routes data packets based on their IP addresses.  Router is mainly a Network Layer device.  Routers normally connect LANs and WANs together and have a dynamically updating routing table based on which they make decisions on routing the data packets.  Router divide broadcast domains of hosts connected through it.
Gateway  A gateway, as the name suggests, is a passage to connect two networks together that may work upon different networking models.  They basically work as the messenger agents that take data from one system, interpret it, and transfer it to another system.  Gateways are also called protocol converters and can operate at any network layer. Gateways are generally more complex than switch or router.  Gateway is used to forward the packets which are generated from the local host or network and but intended for the remote network. If a data packet does not find its destination address in the local network then it takes the help of the gateway device to find the destination address in the remote network. A gateway device knows the path of the remote destination address. If require, it also changes the encapsulation of the packet so it can travel through the other networks to get its destination address.
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.
Network Devices