The Benefits of Software-Based Session Border Controllers

Mobile Musings

The Benefits of Software-Based Session Border Controllers

By Jim Machi, VP of Product Management  |  July 29, 2013

Right now, SBC hardware is implemented at the edges of IP-based networks. While it might seem unlikely for a critical hardware node to morph into a piece of software, the reality is, software-based SBC’s are becoming more viable in the multimedia network – both with service providers and within the enterprise.

Beyond the physical: SBC goes virtual

In a typical scenario, SBC hardware sits on the border of two IP networks, with IP connections on both sides of the box and a physical connection to an IP network. However, that physical connection doesn’t have to be at the exact demarcation point. In fact, it doesn’t even have to be part of the SBC box. Some other device could take care of the physical IP connection, and the IP data stream could then pass through a software-based SBC function that resides elsewhere. For example, a software-based SBC could be resident in a commercial off-the-shelf chassis, where network interface cards handle the connection to the IP network. A series of single-board computers could go into the chassis where the software-based elements could run as an application. The software-based SBC could be connected to a single-board computer in a virtualized environment, or as part of a few applications in a 1U or 2U platform. Ultimately, it could also be in a cloud environment. The actual physical NIC (News - Alert) could be thousands of miles away from the SBC software.

When the software-based SBC is on a single-board computer in a common chassis with multiple other network nodes, users can realize significant cost savings due to the need for fewer hardware chassis. There would also clearly be a reduction in sparing costs, since the COTS components are less expensive and more commonly available, obviating the need for additional on-site sparing. 

Keeping up with voice

Another important consideration is the increase in service velocity. New services are being rolled out more quickly, and agile network elements must be able to keep pace. Software-based network elements enable this nimbleness, due to ease of scalability and the power to add new functions, such as transcoding, on the fly. Media and multimedia transcoding will be required for the next-generation SBC, since an SBC is basically an IP-IP gateway. Transcoding is necessary, since it’s required in a TDM-IP gateway. It’s simple if you think about it from that perspective. 

It’s likely that the needs fulfilled by the SBC will continue to evolve over time. At the moment, the need to transcode HD voice codecs is based on converting it to the more regular codecs. But in the future, we’ll see video transcoding needed as well. Even if it appears that video transcoding is covered, what about when the H.265 video codec comes out in roughly a year? Will you need to buy a new SBC hardware box to cover that? Wouldn’t it be more cost effective to upgrade a piece of software instead?

We should also consider the WebRTC impact on SBCs. There is transcoding required because the WebRTC audio and video codecs are different than those used in networks today. But HTTP-to-SIP signaling conversion is required. Having a piece of software would make this support much easier.

Software SBC for the enterprise

For enterprises, software-based SBCs offer many of the same benefits as above, especially in relation to WebRTC. Many predict that WebRTC will see its earliest widespread deployment in the enterprise. Integration of enterprise apps, whether WebRTC apps or not, could be a differentiator with a software-based SBC. With its ability to scale down, the software-based SBC offers a cost-effective alternative to SBCs that are either too expensive for enterprises or offer too much in terms of session capability. 

Software-based SBCs are convenient, cost-effective and scalable. But can they do what hardware-based SBCs do? Obviously, that is dependent on your supplier, but theoretically, there is no reason why a software-based SBC cannot handle the same functions as hardware SBCs. As voice technology continues to transition to software, you don’t have to lose functionality. Just be sure you’re partnering with experts in this software-ization of hardware.

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

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

Edited by Stefania Viscusi