Secure Global Desktop 4.40 Administration Guide > Getting Started > Introducing the Three-Tier Architecture

Introducing the Three-Tier Architecture

SGD is built around a three-tier architecture model as shown in the following diagram.

Different tiers can reside on the same host, for example, a single UNIX platform host can act as both an SGD server and an application server, but the tiers remain logically independent.

The First Tier: Client Devices

A client device is a piece of hardware that can communicate with SGD using a web browser and the Sun Secure Global Desktop Client (SGD Client).

The web browser communicates with the SGD Web Server on the second tier and displays the webtop to users.

The SGD Client communicates with SGD servers on the second tier and displays the applications that users run.

The Adaptive Internet Protocol (AIP) ensures optimal network usage between the first and second tiers.

The Second Tier: SGD Servers

The second tier might contain a single SGD server, or many SGD servers configured to form an array.

An SGD server is responsible for the following:

• Authenticating users when they log in to SGD
• Negotiating with application servers to authenticate users when they run applications, prompting users for passwords when necessary
• Causing the Sun Secure Global Desktop Client to display applications
• Keeping track of running applications even after users have logged out, so that they can resume them later

The Third Tier: Application Servers

An application server runs users' applications.

When a user clicks a link on their webtop, SGD starts the application on an appropriate application server. Output from the application is redirected by the SGD server from the application server to the client device.

When you tell SGD about an application, you include information about all the application servers that can run the application. SGD load balances between the application servers.

Summary

The following is a summary of the SGD three-tier architecture:

• The first tier contains client devices. Web browsers let users access SGD and display webtops. The Sun Secure Global Desktop Client displays applications that users run.
• The second tier contains SGD servers, which act as a gateway between the first and third tiers.
• The third tier contains the application servers that run users' applications.

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