Application Delivery Controller


In the current era, demanding digital transformations has led to several transforming initiatives like mobility and collaborative mobile workspaces. The new standards in the digital strategy of businesses is leveraging the cloud technology and enhancing application infrastructure to gain better profitability while eliminating data-breach risks. As applications play a decisive role in this regard, it is important to ensure their peak performance, which is critically dependent on traffic management.

Adoption of appropriate networking technologies gains greater efficiency and competitive advantages for the organizations. For the ‘intelligent’ traffic management and the best user experience, the conventional load balancing techniques are not substantial. Now the need is for an advanced solution- Application Delivery Controller.

  1. About Application Delivery Controller
  2. Functions of Application Delivery Controller
  3. Virtual ADCs
  4. What to look for while acquiring an ADC?

1.2 What is an Application Delivery Controller?

As the name suggests, the Application Delivery Controller delivers the application services and controls the interactions between clients and the application servers. The term controller, in this regard, is for the functional management of the data flow between computing systems and application services. This optimizes the application performance, availability, and strengthens the security level.

Application delivery controller is a computer network device, placed in the DMZ, a zone between the outer firewall and a web farm. It optimizes and manages the connection of application servers with client machines.

Conventionally the ADCs have been a physical hardware but now software defined ADCs are also becoming common.
In addition to the conventional load balancing capabilities, ADCs can perform application access management, server health checks, SSL offload, TCP reuse, and RAM caching. Also, it possesses proxy and reverse proxy capabilities, web application firewalls (WAF), DNS application firewalls (DAF), and many others to count.

With all these features, ADCs ensure the most optimized application performance, eliminating the downtime, and making the applications highly available and secure.

1.3 How does the application delivery controller work?

Using the personalized algorithms and customized policies, ADC routes the inbound traffic across a pool of servers. The device administrator can further direct an ADC based on additional guidelines and criteria as which server needs to receive which inbound request. Based on requested file type or keywords, ADCs can inspect the packet headers and auto-route them accordingly.

1.4 ADC vs. Load Balancer

A load balancer simply distributes inbound application traffic across multiple servers whereas ADC is an advanced version of Load Balancer that offers various services across OSI layer 4-7. Application Delivery Controllers perform application acceleration, caching, compression to speed-up the processing of requests, providing an enhanced end-user experience.

ADCs play a big role in securing the network from SQL injection attacks and DDoS threats. With additional capabilities like SSL offloading, application analytics, TCP optimization, application autoscaling, and rate shaping, ADC ensures high availability, security and acceleration of enterprise networks and applications.

2. Functions of Application Delivery Controller

2.1 Load Balancing

Balancing the load means using predefined algorithms to route the incoming requests across various servers. Simple algorithms like round-robin send those requests sequentially, while the advanced ones weigh myriads of factors like location, server capacity, HTTP header fields, content requests and many others.
ADC also possesses the capacities to balance the global server load. Means, it can redirect the traffic to various server clusters, located at different data centers across the globe. ADC routes the requests of a user to the nearest datacenters to minimize the latency and round trip times for the best user-experience. Application Delivery Controllers can be configured in a way to support business continuity during shutdowns, thereby redirecting traffic from affected areas to ADCs at safer co-located areas become seamless.

2.2 Monitoring Health Status

ADCs are relied on for their management capabilities which also extends to confirming a server’s operability and health for the last best configuration. So, if the specific ‘health’ criteria are not being met or the server is having any issue, then ADC routes traffic to alternate servers and this way avoids the disruptions and downtimes.
ADCs also offer the real-time analysis along with the historical data of all the network traffic. It offers the bandwidth usage metrics, round-trip times, WAN and datacenter latency. This helps the desk staff to identify the problems fast, and offer quick solutions.

2.3 RAM Caching

Rather than fetching from the backend server, ADCs store the content locally and reduce server load. This speeds up the content delivery also.

2.4 SSL Offloading

With Offloading SSL processing, ADC decrypts the request and encrypts responses in place of the server. This replaces the backend server as the SSL endpoint for interaction with clients. This even frees the server from the additional load and in turn speeds up the response delivery.

2.5 Compression:

Compression of large static assets like JavaScript codes, graphics, video files, or other multimedia before the delivery, fastens the process and increases network output as a whole.

2.6: DDoS Protection

ADC platforms mitigate and create a line of defense against the DDoS attacks. With the capabilities of SSL offloading, ADCs can find out the potentialities of DDoS attacks based on SSL traffic as the servers and applications are not exposed.

2.7 Central Authentication

Verifying authentication and authorization for clients, the ADCs can also function as a central authentication points

2.8 Multi-Tenancy

Multi-tenancy architecture supports various application tenants or multiple application teams for smarter infrastructure utilization. Enterprises can attain agility and save big by consolidating multiple complex services onto fewer physical or virtual devices. This results in rapid infrastructure provisioning.

3. Virtual ADCs

3.1: What are Virtual ADCs?

ADCs are generally physical hardware devices located at the data center edges. They offer the load balancing features along with others for an optimized performance of the applications running on both- Physical and Virtual Machines.

A Virtual ADC is typically the same software within a hardware appliance but the difference lies in its function, as it runs in a virtualized environment in the cloud.

In contrast with the Physical ADCs, the Virtual ADCs can run on any infrastructure including the public cloud environment.

3.2: Benefits of Virtual ADCs

Benefits of Virtualized Application Delivery Controller include:

Simple Infrastructure: A public cloud is better for delivering quality while scaling globally. In such scenarios virtual ADCs are easy to operate.

Lower Costs: Elimination of the need of hardware acquisition considerably reduces the ADC cost.
Greater Productivity: Cloud-based virtual application delivery supports the faster performance of cloud-based applications, and the end-users can instantly access the services and information anywhere, regardless of their device.

4. What to look for while procuring ADC?

4.1 Optimized Performance and Scalability

Recent explosion in data traffic demands the network systems to be capable of handling ever-increasing rates of application layer traffic. Software, particularly the Operating System in an ADC must be able to handle today’s huge load. So, it’s prudential to go for the ADC that has a multi-core CPU, shared memory architecture, with an OS that can utilize the capabilities to remove bottlenecks.

4.2 SSL Performance:

During setup of a secure connection there is an exponential increase in load on the CPU. Therefore, organizations offload the SSL tasks to ADC as centralizing the SSL certificates reduces the efforts required and the related errors. This strategy also reduces the administration cost when compared with the process of managing SSL certificates on different servers. So, the ADC capable of delivering SSL performance fast and hassle-free is important.

4.3 Application delivery while ensuring safety:

Other important features to be looked in an ADC are global server load balancing capabilities, multi-tenancy with virtualization, DNS firewall, application authentication, and SSL intercept.

4.4 DDoS Protection

In general, DDoS attacks exceed 100Gbps, so the related solution to safeguard the system must support the high connection processing rates. A robust and reliable ADC must be able to offer you such a high processing rate.

4.5 Empowering cloud architecture

For the amazing amenities offered by the cloud technologies, businesses are turning toward this modern computing technique. In such scenarios, the ADC should be considered that can offer SSL offloading, encapsulation/decapsulation, DDos mitigation, distributed services to host/tenant, subscription based L4-7 network service, network virtualization, and effortless integrations with cloud orchestration platforms.

4.6 High-touch client service & support

High-touch client service & support is a fundamental value to be looked for in the ADC vendor. An ideal vendor is the one, offering quick remediation service as and when required. Local language support and scripting support must be a standard part of client support.