HyperText Transfer Protocol (HTTP)

The document describes the seven-layer OSI model, with each layer responsible for certain network functions. The physical layer transmits raw bits over a transmission medium. The data link layer transmits frames between nodes. The network layer delivers packets from source to destination hosts via routing. The transport layer provides reliable process-to-process message delivery. The session layer establishes and manages communication sessions. The presentation layer handles translation and formatting. The application layer provides services to the user/application.

SMTP (Simple Mail Transfer Protocol) is an Internet standard protocol for electronic mail transmission. It was first defined in 1982 and became widely used in the early 1980s as a complement to UUCP mail. SMTP uses a client-server model where the client initiates a connection and sends messages to the server, which then acknowledges receipt. It allows messages to be transferred between machines that are intermittently connected. Common SMTP commands include HELO, MAIL FROM, RCPT TO, DATA, QUIT, and RSET. SMTP can be secured using SSL/TLS to encrypt the communication channel. The latest developments include supporting real-time dynamic content in emails and internationalized email addresses encoded in UTF-8.

TCP and UDP are transport layer protocols used for data transfer in the OSI model. TCP is connection-oriented, requiring a three-way handshake to establish a connection that maintains data integrity. It guarantees data will reach its destination without duplication but is slower than UDP. UDP is connectionless and used for applications requiring fast transmission like video calls, but does not ensure packet delivery and order. Both protocols add headers to packets with TCP focused on reliability and UDP on speed.

HTTP is an application-level protocol for distributed, collaborative hypermedia systems that has been used by the World Wide Web since 1990. The initial HTTP/0.9 version provided a simple protocol for raw data transfer, while HTTP/1.0 introduced MIME-like messages to include meta information and request/response modifiers. HTTP/1.0 did not sufficiently account for hierarchical proxies, caching, persistent connections or virtual hosts. HTTP sits at the top of the TCP/IP stack and uses ports to carry protocols between services, with HTTP typically using port 80. An HTTP message is delivered over a TCP/IP connection by chopping the message into chunks small enough to fit in TCP segments, which are then sent inside IP datagrams

HTTPS is a protocol that combines HTTP with SSL/TLS encryption to provide secure communication between a client and server. It encrypts data sent between a browser and website using a public/private key system. When a client requests an HTTPS connection, the website sends its SSL certificate containing a public key. This begins the SSL handshake where shared secrets are generated to uniquely encrypt the connection. HTTPS is important for securing sensitive communications and establishing trust, as it is used widely on banking, payment, shopping and email sites.

The document discusses the TCP/IP protocol suite and compares it to the OSI model. It describes the layers of the TCP/IP model including the physical, data link, internet, and transport layers. The transport layer uses TCP and UDP, with TCP being connection-oriented and reliable, while UDP is connectionless. The internet layer uses IP to transport datagrams independently. The OSI model has 7 layers while TCP/IP has 5 layers that do not directly correspond to the OSI layers.

The document is a presentation submitted by Harpreet Kaur on data communications. It contains information on various topics related to data communications including an introduction to data communication, components of data communication such as sender, receiver, message, transmission medium and protocol. It also discusses data flow modes, analog and digital signals, types of transmission media including guided media such as coaxial cable, twisted pair cable and fiber optic cable, and unguided media. Finally, it covers networking devices such as modem, hub, switch and router.

HTTP defines a client-server model for communication between browsers and web servers. A browser sends HTTP requests to a web server for web pages and objects. The server responds with HTTP responses containing the requested objects. HTTP uses TCP for reliable transmission and defines request and response message formats. Requests contain headers like Accept specifying object types. Responses contain status codes, headers like Content-Type, and the requested object data.

Web servers are software applications that deliver web content accessible over the Internet or intranets. They host websites, files, scripts, and programs and serve them using HTTP and other protocols. Common web servers include Apache, Microsoft IIS, and Sun Java. Tomcat is an open source web server and servlet container. It implements Java servlets and JSP specifications, providing a Java HTTP environment. Tomcat's main components are Catalina for servlet handling, Coyote for HTTP connections, and Jasper for JSP compilation. While Apache is generally better for static content, Tomcat can be used with Apache for Java/JSP applications.

When we desire a communication between two applications possibly running on different machines, we need sockets. This presentation aims to provide knowledge of basic socket programming to undergraduate students. Basically, this presentation gives the importance of socket in the area of networking and Unix Programming. The presentation of Topic (Sockets) has designed according to the Network Programming Subject, B.Tech, 6th Semester syllabus of Punjab Technical University Kapurthala, Punjab.

Domain Name System (DNS) is a hierarchical distributed database that contains mappings of domain names to IP addresses. DNS allows easy to remember domain names to be used instead of hard to remember IP addresses. It works by matching domain names to IP addresses through a lookup process involving root servers, top-level domain servers and authoritative name servers. This allows computers all over the world to communicate with each other using domain names.

The document discusses the differences between packets and frames, and provides details on the transport layer. It explains that the transport layer is responsible for process-to-process delivery and uses port numbers for addressing. Connection-oriented protocols like TCP use three-way handshaking for connection establishment and termination, and implement flow and error control using mechanisms like sliding windows. Connectionless protocols like UDP are simpler but unreliable, treating each packet independently.