The client tier, which is also known as the presentation tier, is the topmost level used directly by users to view and access information. Requests are passed from the client tier to the application tier, which in turn communicates with the database tier.

The client tier can be accessed from:

• Microsoft Windows desktop PCs that are:
  • Running the Microsoft .Net software framework
  • Hosting EBS client applications
  • Accessing application data through a database connection
  • Running standard web browsers to access websites and services with Hypertext Transfer Protocol (HTTP) or Hypertext Transfer Protocol Secure (HTTPS) through the application layer
• Mobile devices and other desktop operating systems running standard web browsers to access websites with HTTP or HTTPS

The application tier is the middle level of the EBS architecture. This layer is responsible for processing requests for information or updates from the client to the database tier and returning information for presentation to the user.

The application tier:

• Runs the Internet Information services (IIS) web server
• Hosts web pages, including all supporting file structure and files
• Hosts required services, including Web and Windows Service, for processing Workflow queues
• Accesses application data by way of a database connection

The database tier stores information that can be passed to the application tier and on to the client tier.

The database tier:

• Runs the Relationship Database Management System (RDBMS) service
• Hosts the production application database and additional application metadata

Dedicated hardware resources are recommended when deploying the EBS suite of products. The number of servers required will vary based on the size of the organisation and the expected usage patterns.

Examples of how EBS features might be deployed are described in the following table.

Adopting a dedicated server approach is recommended. Advantages of dedicated servers include:

• Improved troubleshooting - it is easier to identify performance bottlenecks on dedicated servers
• Increased software stability - separating operating system versions and component compatibility prevents conflicts between versions
• Improved performance - dedicated server deployments reduce the risk of outages and slowdowns caused by interactions between applications installed on the same server
• Increased security - a security failing of one application will not impact another

Additional application servers may be required for additional third-party software components (for example: database backups or a QAS server).

It is recommended that all internet-facing application servers are hosted within a demilitarised zone (also known as a perimeter network or screened subnet). A DMZ will prevent external users from gaining direct access to a server that is hosted within the private secure network.

It is recommended that the Ontrack Learner Hub website is hosted within a DMZ.

When you choose the multiple-server deployment option to host EBS, load balancing will be required to distribute traffic across servers.

Load balancers are available in the form of software applications (for example: Microsoft Network Load Balancing), or hardware devices (for example: Cisco routers with load balancing capability, content server switches, or Linux LVS).

You can share resources and create test and/or training environments on the same server as your live environment, but it is recommended that dedicated application and database servers are created for each environment. Using dedicated servers for each environment reduces the risk of disruption and optimises performance of the live environment.

Environments can be set up on dedicated hardware or by partitioning virtual server resources.

Virtualisation software (for example: VMware) can be used to host EBS application servers.

All virtual servers must adhere to the recommended memory and processor specifications described in Server State Prior to Tribal Install and Software Requirements.

You can use remote access software (for example: Citrix Remote Access or Microsoft Remote Desktop Web Access) to deploy EBS client software instead of performing local installations on users' desktops.

Benefits of remote access software include:

• Reduced effort - it is easier to deploy EBS patches and EBS clients
• Reduced costs - for remote application provisioning or deployment
• Increased server performance - rapid server, application and capacity provisioning

• Centralised access - users can access provisioned applications from any location

  A local installation of the Citrix web client is necessary for Citrix client deployments

• Increased network performance - users with a reduced bandwidth are able to access EBS applications
• Enhanced security and easier management

Customers using remote access software should be aware of the following known technical limitations that prevent remote clients from accessing local hardware devices (for example: cameras, scanners and so on).

Due to these technical limitations the following functions in EBS Central are unavailable when using remote access software:

• Document Scanner - the following alternative solutions are available:

  • Search for and open an existing scanned file by clicking the Scan Document option on the Documents and Communications ribbon. Click the File option, then the Open Ctrl+O option in the Document Scanner window and navigate to and select the required image in the Open window

  • Use the stand-alone EBS Document Scanning tool, which can be accessed from an application server (for example: C:\Program Files\Tribal\tribal_trbcol\EBS4\EBS_common\components\TribalTech.EBS.Tools.DocumentScanner.exe)

    

• Photo capture - the following alternative solutions are available:

  • Search for and open an existing image file by clicking the Browse for picture option below the photograph control on the Learner Details screen, then navigate to and select the required image in the Open window

  • Use the Import Learner Images wizard (accessed by clicking the Imports button on the System ribbon) to import learner photographs in bulk