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Whether a startup or an enterprise, confidentiality and data security are of utmost importance, especially when it comes to business communication. From tapping into the phone line to placing a bug, traditional phone lines have been riddled with vulnerabilities, and VoIP managed to eliminate most of them. In addition, since the voice signals are converted into digital signals and transmitted over the internet, there are lower chances of interference and tampering. 

However, just like any other thing that is attached to the internet, this call traffic is still prone to attacks. While a firewall installed on the PBX server can help block malicious and unwanted numbers, it doesn’t ensure complete security. Hence, it is wise for businesses to invest in a Session Border Controller to protect the business from these malicious attacks.

What is a Session Border Controller?

A session border controller can be considered a specialized VoIP tool that protects and regulates IP communications flow. It controls the whole security mechanism at the session level to avoid any possible attack on the system. Figuratively, it acts like a doorman sitting on the network’s border and inspects activity for every session. It has some fantastic features to provide extensive security to the IP network and VoIP business, such as,

  • Topology hiding
  • Carrier hiding
  • Protocol validation
  • Calling party address manipulation
  • Called party address manipulation
  • Insertion / Removal of the prefix from SIP headers
  • And more

How does a Session Border Controller work?

SBC is the medium between the PBX server and the service provider’s network. When a call is made from the dialer, softphone, contact center solution, etc., the voice signals converted into data packets are sent to the PBX server and passed on to the SBC. SBC routes the data packets of a session to the public network after normalizing the stream headers or transcoding the data packets with different codecs like H.323, g.711, and g.729. 

Why Do Businesses need Session Border Controllers?

A request is made via the SIP gateway whenever someone makes a VoIP call. The Session Initiation Protocol (SIP) initiates and terminates a communication session. It simply sends the data packets between the two SIP endpoints and holds no power over the ongoing activity in a session. SBC oversees how sessions are initiated, conducted, and terminated and enforces call admission control (CAC) policies and type of service (ToS) marking or rate limiting protocol for QoS.

The SBC solution is capacious to safeguard a VoIP business from all destructive attacks, including but not limited to,

  • Denial of Service (DOS)
  • Destructive Denial of Service (DDOS)
  • Toll frauds
  • Hackers attacks

Compared to the usual internet attacks where malware and hackers can wreak havoc, the terms in VoIP calling attacks are different. Still, they are much more vicious than regular internet security threats. Moreover, these attacks are powerful enough to stall communications and run up operations costs without any returns. Thus, a reliable SBC Solution becomes integral for a VoIP service provider to ensure the highest possible security of the VoIP business and infrastructure.

Today’s SBC solutions are more efficacious than before. Along with the security benefits, the SBC solution also performs some additional operations to benefit the VoIP service providers, such as,

  • NAT (Network Address Translator) Traversal
  • Media Transcoding
  • Codec Transcoding
  • Interoperability of different signaling protocols
  • Interoperability of DTMF
  • And more

The SBC solution’s previously mentioned capabilities enable VoIP service providers to grow their businesses by supporting a variety of media, protocols, signals, etc. The VoIP networks can furthermore provide cross-platform services. This promotes the growth of the VoIP service provider’s clientele and revenue. Therefore, the SBC solution is one of the solutions that business owners really must have.

Different SBC Types

Call Traffic Monitoring

The SBC can be configured to act as a firewall that only handles calls from defined user lists while rejecting others. In addition, it can be set up to monitor calls and track metrics such as the dialed numbers, usage frequency, average call durations, etc. This will detract any malicious DDOS attacks using simultaneous calls to flood the server.

Resource Allocation

SBC can be used to allocate precious server resources to the users based on determined priorities. For example, it can allocate resources to specific users with higher importance, prioritize calls from particular numbers, or distribute bandwidth to provide the best quality of service.

Rate Limiting

In a scenario where the available bandwidth and internet speed may not be enough to handle a specific number of concurrent call traffic, the SBC can intelligently restrict the number of simultaneous calls. This is also possible when you wish to separate signaling and media based on the volume of calls and media being transmitted.

Call Admission Control

Setting up call admission control policies is one technique to protect against Denial of Service attacks. These are based on tracked user traffic profiles and header parsing to determine call authenticity. In addition, the transport layer and secure RTP encryption are frequently configured to secure communication over open networks.

ToS/DSCP bit setting

Putting an emphasis on the Type of Service (ToS) and implementing DSCP tagging is another technique to improve security. The ToS information is provided as four-bit flags in the IP header, and only one bit at a time can be adjusted for the smallest latency, the highest throughput, the highest dependability, or the least amount of money. SIP, H.245, and H.225-based protocols for voice, video, images, text, and data are supported.

Benefits of an SBC

It is a mistake to omit an SBC from a unified communications and collaboration (UCC) network architecture, as doing so exposes the systems to security concerns and can cost an organization precious time and money. The following are a few advantages of using SBC:


A session border controller connects the company’s UCC network platform to the hosted Private Branch Exchange (PBX) service providers, a private network, or directly to the internet. Irrespective of the geographical location, SBCs may be used to route phone traffic over internal IPs, making calls route significantly more quickly and eliminating the need for conventional, individual phone lines.


SBCs increase session quality and user-friendliness. The PBX may have a private IP address and be placed on the LAN. An SBC has access to and can regulate hosted PBX signaling between the PBX and the service provider, offering the capability for signal routing.

Interoperability & Consistency

Incorporating a session border controller to reroute media traffic can improve call quality consistency, reduce lost or missed calls, or both. SBCs also test VoIP lines, monitor sessions, and more to verify that VoIP and video devices work together.


SBCs identify anomalous behavior via pattern analysis. This may include the odd spike in traffic that occurs during a DoS assault when several computers or an excessive quantity of traffic are concurrently attempting to contact the same server from a single IP address.


When a session border controller spots a possible threat, it may quickly stop the issue, inform the CPU of the specifics, and put in place the countermeasure procedures. An SBC can even alert a company’s other sites to the issue, alerting them to potential breaches.

Media and signaling encryption 

The media (voice, video, instant messaging, etc.) and signaling session initiation protocol (SIP) portions of the call are both subject to cryptographic scrambling, also known as signaling encryption. VoIP communications, video conferences, and other SIP-based interactions cannot eavesdrop on, thanks to a correctly configured encryption system.


The methods that hackers use to circumvent security measures are constantly changing. By routinely updating their VoIP security protocols with patches and upgrades, SBC suppliers add an extra layer of security to make UC systems secure.

Wrapping Up

Issues like call connectivity, media codecs transcoding, and protocol handling take the joy out of internet telephony and video on systems without Session Border Controller. The SBC works inconspicuously and handles all these with ease day in and day out to facilitate communications at a lower cost, adding to your revenues. Weighing in the benefits, Session Border Controller is an investment, not an expense, for businesses and VoIP service providers. Vindaloo Softtech offers a Session Border Controller development service and can deploy the robust solution on your existing VoIP calling system. Get in Touch.