It aims to demystify the processes behind the scenes, such as client-server interactions, segmentation, routing, and APIs, enhancing understanding of what occurs beyond the user interface.

Client-server architecture.

This model essentially separates applications into two components(client and server) and allows them to communicate with each other over a network.

The Client is the user’s device(the request side). It sends requests for data, services or resources. It handles the user interface and local processing but relies on the server for heavier operations.

The Server listens for incoming requests, processes them and prepares a logical response. It manages the database, files and beefy/complex computations.

The process:

1. The client sends a request via network protocol(HTTP)

2. The server receives a request and prepares a response.

3. Sends back results(response) to the client

4. Connection management( Is it stateless, Independent, eg HTTPS, or is it stateful, maintaining session data, like using a gaming server)

Benefits

Different applications

1. Switch

   

The client, in most cases, isn’t connected to the server directly; devices such as the switch and router forward packets to the intended destination(Server).

The switch receives the data frames, looks up the destination MAC address in its table and forwards it directly to the server. If the server is on a different network, the switch forwards the frame to a router for further routing.

2. Router

   It examines the destination IP address, checks its routing table and forwards the packet to the destination network. It ensures the client’s request reaches the correct server and the server’s response returns to the client.

3. SYN/ACK

   SYN/ACK is also another good and practical example; it is basically a Three-way handshake in TCP. It occurs in the Transport layer, meaning no session is formed if the handshake is not complete.

   Having no session means that no data transfer occurs, no communication is formed, and no connection is established.

   The switch delivers frames containing TCP SYN, SYN/ACK and ACK packets in the same network, while the router delivers IP packets containing TCP SYN, SYN/ACK and ACK segments between different networks.

4. Firewall

   There are different types of Firewalls, some function in Layer 3, some in Layer 4 and more complex ones in Layer 7. All of them monitor and control inbound and outbound network traffic based on their set rules. Focusing on the Layer 4 one, it inspects TCP/UDP headers like Port numbers and TCP flags(SYN/ACK).

   This enables it to protect the server from SYN flood Protection, which occurs when the attacker sends numerous SYN packets without finishing the connections. It therefore limits the rate of SYN packets being received. A firewall also protects users by using Port filtering, which allows or blocks traffic based on the destination port. It can block port 3389(RDP), block port 22(SSH)or allow 443(HTTPS).

   Another is connection tracking, where the firewall only allows legitimate TCP connections (Complete SYN/ACK), thus protecting the server from unauthorised access.

Load balancer

The load balancer is basically a traffic manager. It ensures incoming network traffic is distributed to available servers. This prevents server overload, thus providing scalability, reliability and top-notch performance. It operates in Layer 7, as it requires interaction with application-layer protocols, such as HTTPS, to perform various functions.

This includes content-based routing, where traffic is routed based on application-layer data, such as file transfers, emails, and APIs. It also allows decryption of SSL/TLS encryption, thus improving the server’s performance.

Note

By mapping key components such as client-server architecture, switches, routers, SYN/ACK processes, firewalls, and load balancers to their respective layers, engineers like you can gain valuable insights into the underlying processes that facilitate seamless communication and data transfer.

This knowledge not only enhances the efficiency and security of backend applications but also empowers you to design robust systems that can handle complex interactions and ensure optimal performance.