Lesson 2	Protocols
Objective	Describe the nature and purpose of protocols.

Nature and Purpose of Protocols

In the context of web technologies, protocols refer to a set of rules or standards that dictate how information is exchanged between different devices or systems over the internet. These protocols ensure that data is transmitted efficiently and reliably, and that all parties involved can understand each other's communications. Some common protocols used in web technologies include the Hypertext Transfer Protocol (HTTP), which governs how web pages are requested and transmitted over the internet, and the Simple Mail Transfer Protocol (SMTP), which regulates the sending and receiving of emails. The purpose of these protocols is to enable interoperability and facilitate communication between different devices and systems on the web. By adhering to common standards and conventions, web developers can ensure that their applications and services can work seamlessly with other systems, regardless of the technologies or platforms involved. Overall, protocols play a critical role in ensuring the smooth functioning of web technologies, and are essential for enabling the rich and diverse ecosystem of online services and applications that we rely on every day.

What exactly is a Protocol?

A protocol is a set of logical rules that define how computers send and receive information. There are two types of protocols:

proprietary and
open.

Proprietary protocols are vendor-specific. For example, AppleTalk works on Macintosh computers. Open protocols are published specifications that anyone can use.
For example, TCP/IP, HTTP, and FTP work on UNIX, Windows-based computers, and Macintosh computers.

Connectionless Protocols: Protocols can be either connectionless or connection-oriented. Connectionless protocols like User Datagram Protocol (UDP) do not maintain their connection to the client. After data is transmitted, the client and server disconnect and no effort is made to verify the data arrived at its destination. Because of this, connectionless protocols are sometimes considered unreliable. UDP and other types of connectionless protocols do have their benefits though. Because they bypass the acknowledgement/verify stages used in connection-oriented protocols they are fast and efficient. For example, suppose you email a co-worker to remind them about an upcoming conference. They might not reply with a confirmation. So, even though your method of delivering the message was fast, there's no guarantee the co-worker completely understood or even received your message. That is the essence of using a connectionless protocol.
Connection-oriented Protocols: A connection-oriented protocol establishes a connection to begin connection and acknowledge all transmitted data. TCP is an example of a connection-oriented protocol. After data has been transmitted, the client remains connected to the server, permitting verification that the data has arrived, and/or to permit particular packets to be re-sent. For this reason, TCP is technically referred to as a reliable connection.

Nature and purpose of Protocols in Web Technologies

In web technologies, protocols are the foundation of communication. They act like a set of standardized rules and agreements that different machines, systems, and applications use to understand each other and exchange information seamlessly. Here's a breakdown of their nature and purpose:
Nature of Web Protocols

Formal Specifications: Protocols are not just ideas; they are rigorously defined documents (often as RFCs - Requests for Comments) that outline precise syntax, message formats, and expected behaviors.
Layered: Web technologies rely on a stack of protocols. Each layer serves a distinct purpose and builds upon the one below it. For example:
- Lower-level protocols like TCP/IP handle basic data transmission.
- Application-level protocols like HTTP govern communication for web browsing.
- Open Standards: Many core web protocols are open standards, meaning they are publicly available, royalty-free, and often maintained by non-profit organizations. This fosters innovation and interoperability.

Purpose of Web Protocols

Reliable Data Exchange: Protocols ensure data packets are transmitted accurately, in order, and without corruption, even across vast networks.
Structured Communication: Protocols define how requests and responses are formatted. This allows web browsers and servers to understand each other's messages.
Error Handling: Protocols have built-in mechanisms for detecting transmission errors, requesting retransmissions, and signaling problems to applications.
Flow Control: Protocols help manage the rate of data transmission to prevent overwhelming network components.
Security: Protocols like TLS/SSL provide encryption and authentication, essential for ensuring privacy and data integrity on the web.
Extensibility: Protocols are often designed to be extended with new features and capabilities as needed, supporting the evolving nature of the web.

Examples of Key Web Protocols

TCP/IP Suite: The backbone of the internet.
- TCP (Transmission Control Protocol): Provides reliable, ordered data streams.
- IP (Internet Protocol): Handles addressing and routing of packets.
HTTP (Hypertext Transfer Protocol): The foundation of web browsing. Defines how clients request resources and servers respond.
HTTPS (HTTP Secure): Adds encryption and authentication (TLS/SSL) to HTTP for secure communication.
FTP (File Transfer Protocol): For transferring files between systems.
SMTP (Simple Mail Transfer Protocol): Governs email transmission.
DNS (Domain Name System): Translates human-readable domain names into IP addresses.