GuidesWhat Is a Client-Server Model? A Guide to Client-Server Architecture

What Is a Client-Server Model? A Guide to Client-Server Architecture

The foundation of modern networking is the centralized process and IT framework known as the client-server model.

For over 50 years, servers have been the machines and mechanisms to process end-user requests and deliver specific digital resources. These requests include anything from a Google search on a smartphone to a remote employee accessing confidential company information.

In both instances, a user device triggers a request to another machine, like a network server, which receives, filters, processes, redirects, or any combination of these actions before returning the adequate response.

This article looks at everything you need to know about the client-server model.

What Is the Client-Server Model?

The client-server model is a network architecture that describes how servers share resources and interact with network devices. For modern enterprises and data centers, many servers facilitate processes like email, printing, internet connections, application hosting, and more.

The client-server model describes how network devices like workstations, laptops, and IoT devices — known as clients — make requests to network machines or software capable of completing the request, known as servers.

Though servers historically have been physical appliances like rack servers, data center trends show administrators increasingly deploy virtual servers for a range of workloads.

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What Are the Components of a Client-Server Model?

All client-server frameworks contain three primary ingredients: clients, servers, and the networking devices to connect the two segments.

Client
Examples
Server
Examples
Networking Device
Examples
Workstation
Database Server
Hub
Desktop
DNS
Bridge
Laptop
Web Application Server
Switch
Tablet
File Server
Router
Smartphone
Proxy Server
Gateway
IoT Device
Virtual Machine
Modem

Clients

Enterprises once relied on workstations that shared a single operating system, but today’s IT environment strives for interoperability between systems, devices, applications, and products.

Because network clients are increasingly heterogeneous device and OS types, administrators have the added responsibility of ensuring compatibility.

Servers

The hyper-focused machines delivering IT resources to clients are the physical, virtual, and cloud-based servers housed in modern data centers. Servers are the central authority for several essential digital processes that enterprise organizations rely on.

Networking Devices

The framework calls for physical or wireless networking devices like hubs, switches, and routers to connect servers, clients, and resources.

With the connection between clients and servers established, administrators can configure how client devices make requests and designate servers to complete specific tasks.

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How Does the Client-Server Model Work?

An operational client-server architecture facilitates the following process:

  1. The client submits a request through a network-enabled device.
  2. The network server receives and processes the request.
  3. The server delivers a response to the client.

Though simple, the client-server model is widely applicable and relevant to anyone seeking to understand content delivery networks (CDN) or the mechanics of edge networking. As server capabilities move closer to the network edge, the client-server process is physically closer to end-users.

graphic showing the client-server model
Designed by Sam Ingalls, © ServerWatch 2021

Client-Server Model Examples

Facilitating Email

Communication is essential to enterprise organizations, and snail mail can’t compete with the speed and reliability of electronic mail. The hosting of email communications for an organization or network by a specific server has been the longtime industry choice to control particular email accounts and activity.

Through protocols like IMAP, POP3, and SMTP, administrators can establish a system that facilitates, secures, and maintains email communications.

When using their email accounts, staff are the clients making requests to send emails, upload attachments, and store contacts to an email server.

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Accessing Web Content

When a web client wants to access a specific website, they enter the URL, and the browser requests an IP address from the domain name system (DNS). The DNS server assigns the user an IP address for identification and delivery of results.

By navigating to the website, a client triggered specific web content that the user can only access via an HTTP response provided by a web server.

In this case, the end-user is the client presented with digital content. The DNS server and web server establish and facilitate the connection to a database hosting the web content.

Advantages and Disadvantages of the Client-Server Model

Advantages
Disadvantages
Central access and control of data
Less control of some network devices
Efficient, scalable, and organized system
Upfront cost and implementation
Load balancing for optimal performance
Technical expertise for ongoing maintenance
Redundancy and data recovery options
Servers at risk of DoS attacks
Interconnected network of devices
Clients are attack vectors when breached

The Different Types of Client-Server Architectures

The four types of client-server frameworks are representative of how the client-server relationship evolved with networking advancements.

1-Tier: All-in-One System

All client-server configuration settings, user interface, business logic, and database logic sit on network devices in the base client-server architecture. Often limited to smaller networks, 1-Tier frameworks include presentation, business, and data access layers on the same machine.

2-Tier: Client and Server

2-Tier architectures add a server to the mix and separate the presentation layer to a user interface, where the client makes requests outside its capabilities. Clients and servers take on more business and database logic at varying levels, providing administrators some control.

3-Tier: Middleware

To further protect and enrich the 2-Tier architecture, this framework incorporates middleware between the client tier (presentation layer) and the server tier (database layer).

This application layer provides a third tier, enabling more complex management of business logic. Examples of middleware like web application servers offer load balancing, increased storage, and security.

N-Tier: Multitier Architecture

Working off of the 3-Tier architecture, N-Tier describes the further use of middleware to segment network traffic and functions. Though this comes with greater complexity, modern enterprise organizations require multitier architectures’ flexibility, scalability, and security.

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Peer-to-Peer vs Client-Server

Though the client-server framework is the most popular distributed architecture, the most common alternative mentioned is peer-to-peer (P2P) networks.

Unlike the client-server architecture, which offers a centralized flow from an organization’s servers to staff, stakeholders, and clients, a peer-to-peer network is decentralized. Network devices don’t align with a specific, dedicated server. Instead, P2P networks include network devices (clients) known as nodes that submit and service requests between each other.

Because P2P networks like blockchains work in a distributed fashion, connectivity is critical to operations. Relative to traditional networks, nodes tend to be more heterogeneous and share less data across the network.

The client-server model is more expensive to set up and maintain, but the reliability and scalability of the centralized framework consistently outweigh the downfalls of peer-to-peer frameworks.

The Distributed Architecture of Choice for Enterprises

With benefits like centralized data control, workload balancing, added security, and redundancy, the client-server model is the near-universal framework for SMBs up to enterprise organizations.

When compared to P2P networks, it’s easy to see why the client-server model scaled digital operations for networks to this point. As organizations grow, adopting additional tiers of client-server architecture is necessary to maintain IT infrastructure and secure data integrity properly.

To serve millions of customers and stakeholders globally, enterprises need a robust distributed framework that only the client-server model provides.

Read next: How to Achieve High Availability Architecture

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