March 24, 2020 Last updated April 1st, 2020 698 Reads share

VoIP Session Border Controller a Must For VoIP Service Providers

Image Credit: DepositPhotos

VoIP service providers interface with bulk telecom carriers on one side and with their wholesale and retail customers on the other. A typical setup includes class 4/5 Softswitch at the core with the session border controller as the outlier to provide security and other important functions. The SBC solution may be hardware-based but in today’s environment, software SBC is the preferred way to go since older hardware cannot be upgraded and may not be able to handle the volume of traffic or VoLTE or the emerging 5G technologies. Even within the software category of SBC solutions, there are different flavors and how efficiently VoIP services work depends to a large extent on the technical features of the SBC and its implementation. For VoIP service providers the session border controller is an absolutely indispensable network element from various perspectives.

Capability to Handle All Media Protocols and Transcode Codecs

Analogue PSTN lines still exist but VoIP has brought in its wake various protocols and media codecs all of which must be handled seamlessly to avoid call drops or call quality losses. Just how complex it is can be gauged from the various protocols and codecs in use:

  • Media Gateway Control Protocol is integral to VoIP. VoIP networks must connect with PSTN lines and here the MGCP plays a crucial facilitating role. It uses a session description protocol to specify and handle media streams as well as the real-time transport protocol. H.248 is another protocol that facilitates interconnect between PSTN and packet voice data networks.

  • SIP is used in VoIP to handle sessions that include voice, messaging and video in conjunction with stream control transmission protocol, transmission control protocol and user datagram protocols secured with transport layer security. Unfortunately, there are various flavors of SIP and SIP headers have vulnerability flaws. SBC plays a crucial role in normalizing the SIPs and in encryption.

  • H.323 is still in use alongside MGCP and SIP and the SBC.

  • Then there are various other codecs such as G.726, G.729, GSM, Skype’s SILK and Speex.

  • If that is not enough there is now WebRTC to consider, increasingly being used for audio video chat and conferencing via a browser.

A call originator may use a specific codec whereas the receiver may not have that codec in use. SBC simply transcodes the codecs and facilitates connections otherwise calls do not connect.


This could be the most important reason for VoIP service providers to have a smart SBC at their network edge. VoIP traffic grows and as it grows hackers increase attacks. A typical attack such as DoS or DDos can cripple the service and simply make it impossible for calls to go through. It affects customers and the VoIP service provider’s reputation as well as revenues. There are other security aspects too such as attempts to tunnel in and steal data, spoofing, identity theft and listening in that compromise security of business conversations and networks in one way or another. The SBC stands guard and identifies as well as blocks any such attempts besides providing solid encryption for voice data packets. Now add mobile phones in the GSM and VoLTE segments to the mix and vulnerability increases were it not for the SBC. Huawei’s study shows that peak attack traffic is increasing at a rate of 50%. VoIP services need not just SBCs that can prevent attacks but an AI-powered SBC that learns from patterns and becomes smart enough to identify attempts long before they become a real threat.

Quality of Services

  • SBCs are tasked with hiding internal topology from external networks, thus providing a measure of protection. Further, SBCs also handle the vital task of network address translation traversal or NAT. You have a single public IP address whereas internal IP addresses are hidden but calls go through and are received in a seamless fashion. Here again, there are various techniques such as socket security, TURN, hole punching and STUN, to name a few. How and which of these are integrated into the SBC by the SBC developer makes a difference to the quality of service.

  • Packet prioritizing and handling diverse types of data packets that include voice, video, chat and data is an absolute must. Typical implementations of built-in proxy call session control and charging rules function in the SBC ensure the seamless quality of service. Since calls or data can include 2G, 3G and LTE networks, the SBC must also have ATCF/AGTW to assure updated media information.

  • Another important function is that of prioritizing packets. Huawei data indicates VoLTE subscriptions will see a year on year 145% increase which means SBCs must-have capabilities to take on huge volumes of data and also prioritize calls.

  • Along with prioritizing calls the device also plays a crucial role in routing traffic through the least cost network

Though not essential you can expect software-based SBCs to offer real-time monitoring of traffic, the capability to configure details and set permissions and to bill as well as accept payments. The analytics feature gives you a handle on all that is going on and lets VoIP service providers optimize operations.

VoIP office phone -DepositPhotos

Hiten Dudhatra

Hiten Dudhatra

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