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Application Delivery Controllers

Application Delivery Controllers


The Application Delivery Controller (ADC), formerly named AFE (Application Front End) and Server Load Balancer (SLB) respectively represents the unique point of access and control of how an application is delivered, especially for web applications.

Beside traditional load-balancing Layer 4 OSI the ADC incorporate today several useful features:

  • Intelligent load balancing for web applications, based on server availability and applications response time
  • Web content compression, caching and HTTP acceleration for better application response time
  • SSL for secure transport and authentication
  • User authorization – LDAP and RADIUS are good examples
  • Security – DoS protection, Web Application Firewall and IPS functionalities help protect the applications behind.
  • Programming and scripting possibilities for custom applications
  • Integration with virtualization technologies (grid computing), enabling virtualization in environments where was not possible before.

User Benefits

The ADCs have a more and more important role nowadays, as most of the applications are webified or moved to the cloud. Consequently, the ADCs are enriched with supplemental functionalities like authentication, authorization, etc. 
The user benefits derive from the functionalities required above:

1. Improved user productivity

  • Faster application response times
  • Caching and compression avoids WAN and server upgrades

2. Security

  • Increased security for applications with Web Application Firewall
  • Single point of control for user access with integrated SSL technology
  • Acting as full reverse proxy, the servers are “hidden” after ADC, which terminates all client connections
  • Protects against DoS and DDoS

3. Enablement

  • The scripting language can parse and rewrite the content and the flow / session parameters so that applications (web) can be made available also for non-standard access devices
  • Enable the roll-out of new services and applications in the network
  • Enable system and application upgrades without service interruption and during the work day

4. Consolidation

  • Enables server consolidation into one location
  • Less servers used to serve the same number of users
  • Avoid server upgrade

The ADC is deployed inline, in front of application servers and serve as a gateway (the ADC can be named also full reverse proxy cache) to these applications.


Business Impact

As the ADCs represent a key element in the today infrastructure, as they bind network infarstructure, applications and users, several considerations are to be taken into account when deploying such a solution:

1. Network Integration

  • Proper configuration – unproper configuration on the ADC may result in business processes outages
  • User authentication integration – organizations should integrate the ADC also with the authentication methods – certificates, token, OTP,etc

2. Design

  • The solution should be deployed either in High Availability pair, either as fully redundant blade chassis

3. Dimensioning

  • the solution should be properly dimensioned in order to accommodate user and application traffic also for future needs
  • the security audit functionalities can result in severe performance penalties.

Products supporting this technology

Radware Riverbed
  • manufacturer