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A data exchange protocol is a rule set and standards that different systems use to communicate and share information. The protocols help in organizing data transfer more effectively. They manage error checking, data compression, and encryption, ensuring data reaches its destination intact and safe. Protocols are often used to support the application architecture's functioning.
What are protocols?
Protocols regulate how information is exchanged, making sure the data flows smoothly and securely between two points. They provide a standardized framework allowing computers and devices to communicate with each other, regardless of their hardware, software, or operating systems.
Knowing the protocols equips the tester with a good understanding of the complexities of networking and data transfer basics. This knowledge will help to create better test cases, evaluate the data transfer between systems, and identify optimization areas.
Application layer protocols - types of protocols
One of the popular communication protocols we've already mentioned is Hypertext Transfer Protocol or HTTP. It's the World Wide Web's backbone protocol and enables communication between web servers and browsers. Whenever you type a URL in a browser or send a webpage request, HTTP ensures secure and efficient data transfer. We will discuss this protocol more in the next topic.
Another familiar protocol is File Transfer Protocol (FTP). As suggested by its name, it's all about transferring files between systems. It's widely used when you need to upload or download files from a remote server, such as when updating a website or sharing large files.
Here’s a simple example to help you visualize how FTP works. Imagine you have a website with various files: HTML, CSS, images, etc. You connect to the remote server using FTP software and enter credentials. Once connected, you can browse through the local files and navigate the server's filesystem. By dragging and dropping files, you can upload or download them seamlessly. FTP can also be used for backing up important files and data. By connecting to a remote server via FTP, users can send their files to a secure location for safekeeping. This ensures that important data remains accessible even in the event of local hardware failures.
Various software applications require periodic updates to introduce bug fixes, security patches, and new features. FTP simplifies the process of delivering these updates to end-users. Developers can upload the updated software files to an FTP server, and users can then download and install the updates on their devices.
Simple Mail Transfer Protocol (SMTP) is a set of rules that computers use to send and receive emails over the internet. It takes an email message and sends it through several servers, known as mail transfer agents, until it reaches the recipient's email server. This entire process is known as email delivery.
SMTP also manages the authentication and security aspects of email delivery. It ensures that the email originates from a reliable source and protects it from interception or modification during transmission. This is crucial in preventing spam and unauthorized email access.
Look at an example to understand how SMTP works. Imagine you're sending an email to your friend. When you hit send, your email client contacts the SMTP server, usually provided by your internet service provider (ISP) or email service, to send the message. The SMTP server checks the recipient's email server address and starts transferring your email toward it. Once the recipient's email server receives the email, it stores it until the recipient retrieves it.
Many companies and organizations use email newsletters to reach their customers or subscribers. SMTP enables the bulk sending of email newsletters by connecting the sender's email server to multiple recipient email servers. This ensures the newsletters reach the intended audience reliably.
Applications often need to send automated notifications to users via email. These can vary from password reset notifications to order confirmations. SMTP enables applications to connect to email servers and deliver these notifications to the recipients.
DNS — Domain Name System. DNS is like a personal internet address book, translating domain names into IP addresses. Whenever you type in a website URL, like "www.example.com," DNS finds the corresponding IP address.
Here's a practical look at how DNS works. When you enter a domain name in a web browser's address bar, your computer sends a DNS query to a DNS resolver. The resolver acts as an intermediary between your computer and the DNS server.
The resolver forwards the DNS query to the appropriate DNS server, which looks up the domain name in its database. If the server finds a match, it returns the corresponding IP address to the resolver. The resolver then sends the IP address back to your computer, allowing it to connect with the intended website. All of this happens within milliseconds, making web browsing effortless and seamless.
In large-scale applications experiencing high traffic, DNS is used to implement load balancing strategies. By assigning multiple IP addresses to a single domain name, DNS can circulate and distribute the traffic across the available servers, ensuring an optimal user experience. In case of a server failure, DNS can quickly redirect traffic to a backup server, ensuring uninterrupted service.
The role of protocols in application architecture
So why are protocols used in application architecture? Well, imagine an application with multiple modules or services, each performing a specific task. For these modules to work seamlessly together, they need to communicate and exchange data. This is where protocols come in.
By following these protocols, developers ensure that different parts of an application work harmoniously, regardless of their underlying technologies or programming languages. Application architecture refers to an application's complete design and structure, including its components, their interactions, and how data flows between them. When designing an application's architecture, developers need to carefully consider the protocols they will use. Different types of application architectures need different protocols.
In a client-server architecture, protocols like HTTP or HTTPS are commonly used for communication between the client side and the server side. These protocols define how requests and responses are sent and received, enabling users to interact with the application and receive the information they want.
Microservices often require inter-service communication that goes beyond simple request-response interactions. This is where we use message queue protocols, like Advanced Message Queuing Protocol (AMQP) or Simple Messaging Service (SMS). This allows messages to be placed in a queue and processed asynchronously, meaning that the sender and receiver don't need to communicate at the same time. This protocol helps decouple the sender and receiver, ensuring that messages are not lost if the recipient is unavailable and enabling better scalability and reliability in distributed systems. Microservices often also use gRPC or REST protocols.
gRPC – Google Remote Procedure Call – a communication protocol allowing different systems to communicate with each other over a network. It allows remote services to call functions or methods from another system quickly and efficiently. gRPC provides a way for various programming languages and platforms to interact seamlessly, making it easier to build distributed systems.
Representational State Transfer – REST – is both a protocol and an architectural principle set. RESTful APIs adhere to a constraint set to ensure stateless and scalable communication. The communication happens through standard HTTP methods, such as GET, POST, PUT, DELETE, and PATCH. REST allows services to exchange data in various formats like JSON or XML.
HTTP can be used for all the application architecture protocols. When a monolithic app needs to request data from a server or send data back, it uses HTTP to make that happen.
Another protocol that monoliths often rely on is the Structured Query Language – SQL. It is all about interacting with databases. It allows a monolith's components to exchange information with a database using a familiar query language. This way, the app can store and retrieve data efficiently.
How do these protocols work in a monolith? Imagine a monolithic app needs to display a list of blog posts on the user interface. When the user opens the app, the front-end sends an HTTP request to the back-end, specifying the desired action – fetching the blog posts. The back-end receives this request, translates it into a corresponding SQL query, and sends it to the database, which retrieves the relevant blog posts. Finally, the back-end returns this data to the front-end in an HTTP response form, which is then displayed on the user interface.
Conclusion
The work of protocols outlines the data exchange process within the application architecture. Besides, protocols define a certain checks set for testers, allowing them to detect component interaction errors. The protocols set determines the application functionality that needs to be covered by tests.
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