Application Acceleration

Application Delivery Network

What is an Application Delivery Network?

An Application Delivery Network is a suite of technologies that are deployed together to provide application availability, security and acceleration.

Business networks of organisations, partners and customers rely on the availability, performance and security of mission-critical web applications such as Enterprise Resource Planning (ERP), Customer Relationship Management (CRM), databases, email, VoIP and Video-conferencing, etc.

However, the performance of applications is vulnerable to database networks, slow response times, server and network overloads.

ADN uses the following techniques to enhance application delivery:

Application Delivery Network Optimisation Techniques

TCP Multiplexing

A technique for improving Web-server performance, by consolidating incoming TCP/IP requests to reduce the number of times server connections have to be made.

User requests sent to the server are intercepted and consolidated to reduce the number of times server connections have to be made.

TCP Optimisation

There are a number of RFCs which describe mechanisms for improving the performance of TCP. Many AND implement these RFCs in order to provide enhanced delivery of applications through more efficient use of TCP.

Data Compression and Caching

ADNs also utilise compression when delivering applications via a WAN or particularly congested high-speed data link.

Application Delivery Network Reliability & Availability Techniques

Advanced Health Checking

The ADN can check the state of the server on which the application is hosted and the status of the application it is delivering. The ADN can determine whether the content returned by the server is correct and should be delivered to the client.

Load Balancing Algorithms

The ADN can determine whether an application is available to respond to a request according within specified routing rules known as algorithms. Some algorithms include Round Robin, Least connections, Fastest Response Time.

Fault Tolerance

The ADN can designate specific servers as a back-up in the event that a primary server(s) fails. By automatically switching to another back up server, traffic can continue to flow ensuring business continuity.

Application Delivery Network Security

Transport Layer Security

SSL (Secure Sockets Layer) can be used through an ADN to ensure the security of all application traffic. This prevents any hackers from decrypting the encrypted traffic.

Application Layer Security

The ADN can prevent potentially useful information regarding the software and hardware infrastructure from being exposed to the client. This is known as resource cloaking. ADNs can also include application firewall functionality to further secure applications during the delivery process.

Network Layer Security

The ADN can protect against network layer by obtaining sufficient client information before making a routing decision and also by filtering traffic.

Traffic Management

With traffic management functionality, the ADN can analyse, block, shape and prioritise traffic.

An ADN enhances the delivery of applications across the Internet using the techniques below.

Application delivery uses one or more layer 4-7 switches (multilayer switch) to intelligently distribute traffic to a cluster (also known as farm) of servers. The Application Delivery Controller (ADC) is assigned a single virtual IP address (VIP) that represents the cluster of servers. Traffic arriving at the ADC is then directed to one of the real web servers based on a number of factors.

An ADN provides the advantages of load distribution, increase server capacity, improved scalability, security, and increased reliability through application specific health checks.

At the core of the ADN is the Application Delivery Controller (ADC) – also referred to as web switch, content switch or multilayer switch. This is a traffic management device which distributes traffic among a number of servers or geographically dislocated sites based on application specific criterion.