The Low Down on Session Border Controller in VoIP and Why You Must Have It

Controller in VoIP

VoIP is the de-facto platform for communications with value expected to exceed $ 93 billion by 2024. It is not surprising given that you can save anywhere from 40% to 90% on calls besides getting access to rich media communications. VoIP stands for Voice over Internet Protocol and IP is notorious for being vulnerable to security hacks. This is one of the main reasons you need a session border controller in VoIP at your network edge. There are other reasons as well. So, what is the SBC software and why do you need it for your business


SIP or session initiation protocol underlies voice communication along with real time transport protocol. SIP has three components comprised of proxies, user agents and registrar servers. It would be lengthy to explain how these three components interact to enable voice calls over the internet but what happens is that the SIP message has a first line, a header and message body. It is open and vulnerable with the header containing information about identification of user agent client and SIP path.

SIP also faces NAT issues since those who are behind NAT will not enjoy the functionality.

SIP has different flavors and compatibility issues may arise. 

Hackers can easily decipher details due to the shortcomings of SIP. 

The session border controller enters the picture to address and overcome the above SIP related issues. 


Take the case of Enterprise A. It has an internal LAN network with a firewall and it uses Controller in VoIPcommunications through a VoIP service provider. The assumption is that since the VoIP service provider has a session border controller at their end Enterprise A need not implement SBC solution. This is fallacious and leads to a host of issues: 

  • Vulnerability of Enterprise A network since hackers can tunnel in through open ports and steal data, launch DoS/DDoS attacks, inject malware or eavesdrop or make use of the VoIP network. 
  • Inability to connect calls in case of protocol and codec issues and 
  • Network address traversal or translation (NAT) issues. 

The session border controller takes care of all such issues, sitting at the “border” or edge of the network, which is why you have “border” term in session border controller. 

Controller means the software controls data packets in each session. It can hide SIP headers and it can hide ports. It can control access and it can convert media codecs and protocols to facilitate smooth communication. 

A session is when a conversation is initiated, continues and is terminated. The session may go beyond voice to include media like video and data. 

In short, you could say that the SBC is a watchdog and a facilitator too. 

Why do you need SBC software?

The session border controller, as can be seen above, is multi-functional and absolutely indispensable if your enterprise has VoIP network as part of an overall network. Carriers and VoIP service providers routinely integrate SBCs along with Media Gateways and softswitches. 

Security: Large enterprises cannot afford to compromise on security. Without Controller in VoIP you can make do with firewalls but VoIP changes the equation. The underlying technology could open up ports that will let attackers launch DoS attacks, introduce malware, steal data or misuse your VoIP.  SBC solution provides greater security since it hides internal topology, hides or encrypts SIP headers and makes the internal network opaque to external network. The SBC is responsible for TLS and SRTP encryption that defeats attempts at eavesdropping. 

NAT traversal: Firewalls and internal security or configuration can pose problems for VoIP traffic. Calls may not go through or you may not be able to receive calls due to network address traversal or translation issues. Here again, the session border controller comes to the rescue, seamlessly facilitating NAT. 

Facilitator:  In the beginning there was only voice traffic using established media codecs and protocols. However, today’s world of VoIP traffic is different. You have voice traffic based on a variety of media codecs and protocols with user at one end using a different set and user at the other end using another set. Mismatches can cause poor audio quality or even disallow connection. The SBC software seamlessly takes care of interoperability 

These are the main functions that the SBC carries out. Besides, a well designed and modern SBC solution will take care of:

  • Intelligent call routing and least call routing
  • Integrated billing and accounting if required
  • Seamless integration of a range of devices including mobiles using GSM/LTE technologies

Leaving out the SBC could be a costly decision. A Holmes report states that resultant poor communication costs businesses about $ 37 billion and communication barriers represent a loss of $ 62 million by way of reduced productivity. Should you become the victim of a DoS or ransomware attack the loss to your enterprise could be quite high. 

If you use VoIP in your business set up then make it a point to include SBC Solutions to secure and facilitate VoIP communications. Get it from the right vendor and enjoy peace of mind as well as enhanced productivity.

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