The Case for a Real-Time Application Delivery Controller

What�s Next

The Case for a Real-Time Application Delivery Controller

By Jim Machi, VP of Product Management  |  April 04, 2016

As the telecom infrastructure world moves to software, there are still anti-pundits that question the ability of software to scale and be reliable. Call them hardware bigots, but their position is totally understandable. Hardware has scaled in telecom for decades, and hardware architectures have proven to deliver five 9s reliability. However, the data and IT type architectures utilizing commercial off the shelf equipment and oversubscription models have proven just as reliable. In these architectures, if a unit goes down, there are others available to take up the slack. And with the stacking of these units, they have proven to be just as scalable as well.

This has required software to manage and control the COTS and/or software-based offerings. And as NFV has moved telecom infrastructure inexorably more toward software, these load balancing and scalability architectures are becoming more important.  Again, we need to look to the data world for guidance. Building large-scale and highly-reliable applications was a challenge that the web application world has solved with application delivery controllers, essentially intelligent load balancers for web, database, and other network-based traffic.

This model can be applied to real-time telecom communications. However, specialization will likely be required in the real-time SIP communication world because the requirements of voice and video calls are different than the requirements of accessing web pages or getting email. Real-time traffic is critical and cannot be treated as other network-based traffic. We’ve already seen in management of software media servers  specs from the IETF (RFC 6917) and 3GPP (TS 23.218) that call for a media resource broker to direct traffic to and from telecom application servers and media servers. 

For ADCs that are deployed in a real-time telecom software-based infrastructure environment, specialization is required because there are some shortcomings for web-focused ADCs – namely, poor handling of RTC protocols, no support for WebRTC, and

SIP support issues including the ability to intelligently handle layer 5/6 traffic and SIP 3xx and 4xx messages. These are critical for deploying an ADC (News - Alert) throughout the IP infrastructure when real-time voice and video are deployed.

That leaves two choices: to deploy a new real-time ADC next to a web-focused ADC, (which is a great choice if you already have an ADC deployed), or deploy the real-time ADC in the telecom-focused environment (which would also be able to handle the web- based ADC requirements). 

What are some of the use cases for a real-time ADC?

Application-aware contextual routing is an important element of a load balancer. It intelligently distributes traffic associated with a service (e.g., SIP) across one or more available service nodes in the network. When key services such as SIP and HTTP are involved, a deeper inspection to extract insights into sessions and transactions can occur so routing of messages that belong to a particular session and/or transaction can be directed to specific service nodes. This contextual routing is beneficial in several use cases, such as always being able to route SIP messages belonging to a conferencing session to the service node hosting that conference, or in routing-associated media stream to a common media server.

Increasingly, encryption is becoming a key requirement for securing RTC and non-RTC traffic. For instance, encryption is called for in the emerging WebRTC-enabled communication solutions. Depending on the level of sophistication of the encryption and decryption techniques employed, they can result in a significant computation overhead, causing degraded performance. Furthermore, due to different product upgrade cycle and maturity, all the nodes in a network are unlikely to provide the same levels of encryption support. This makes it hard for network administrators to impose uniform encryption requirements across all supported services. An efficient encryption engine designed for processing large volume of encryption traffic is required. A real-time ADC can be configured to offload encryption overhead from the individual service nodes, which can help to significantly improve application performance.

Finally, communication networks often depend on multiple media control protocols, resulting in complex, internetworking, and integration challenges. Real-time communication protocol conversions such as between MGCP and SIP need to occur, allowing applications to interoperate across protocols.

The telecom ecosystem has always responded to the challenges the new networks bring forth. New products and new ways of thinking have spurred innovation since I’ve been part of this industry. As telecom and IP continue to converge, specialization of existing elements will be required as voice becomes a component, not the reason for existence, of the overall network. The real-time application delivery controller is one example.

Jim Machi is senior vice president of product management and marketing at Dialogic (News - Alert) Inc. (

Jim Machi is vice president of product management at Dialogic Inc. (

Edited by Stefania Viscusi