Session Boarder Controller (SBC) and E-SBC Explained in Layman's Terms

Session Boarder Controller is a firewall for VoIP trafficManaging VoIP with Session Border Controllers (SBC) and Enterprise Session Border Controllers (E-SBC)
Even while Voice over IP adoption continues to rise, a lot of confusion still persists when it comes to understanding how VoIP actually works ‘under the hood’. And while you may not need to worry about managing the individual components of a VoIP network if you work with a company like Mushroom Networks, it helps to understand how those components work together to provide the service.

Understanding Session Border Controllers (SBC)
In any VoIP call (or any voice call, for that matter), before the call can be made, an ‘agreement’ has to be made between the two phone systems on either end of the call, as to how the two will ‘talk’ to each other –  i.e.., what signaling protocol they’ll use, and other parameters that need to be established in order to create a successful call. Without this ‘agreement’, the call will either be of low quality or not work at all.

A Session Border Controller (SBC), then, manages the signaling between two VoIP systems, and establishes the parameters that will make for a successful call. The SBC sits in-line between a given company’s VoIP network and the larger WAN or external voice network. So, when a call is made on the VoIP network, the SBC establishes the signaling protocols between the enterprise and service providers that will carry the voice traffic, to ensure that the calls are set up efficiently and flow smoothly.

SBCs are used in one of two primary ways – they can either set up the calls, and then allow the end-user systems to transmit the voice data directly, or they can act like a proxy, whereby they not only establish the call session and signaling, but also receive and re-transmit the voice traffic itself, acting as a middle-man for both the session traffic and the voice traffic. Both designs have their benefits and drawbacks, and not all SBC’s are capable of forwarding media traffic in addition to session traffic.

Technically, VoIP calls can be made without an SBC. But without the use of an SBC, the enterprise typically loses both flexibility in the types of calls that can be made, and loses quality and reliability in their network.

SBCs perform other functions as well. One of the most common functions provided is security, whereby the SBC acts as a firewall or application-level gateway, controlling and monitoring VoIP traffic from a security standpoint as well as a performance standpoint.

SBCs and Enterprise SBCs
The Enterprise Session Border Controller, or E-SBC, is an SBC that’s deployed on premises into an enterprise. SBCs are typically deployed by the VoIP service provider, interface with the customer’s enterprise network, and are managed by the service provider. E-SBCs, in contrast, are located and managed from within the enterprise, and are managed by your internal IT staff.

The primary advantage of E-SBCs is that they can be customized to do more than simple VoIP calls. As the use of Unified Communications, rich media videoconferencing, multiple providers, and cloud platforms increases, so does the need to manage those communications from an SBC that is controlled and managed directly by your enterprise, instead of a network service provider.

E-SBCs work in environments with multi-provider, multi-service configurations, because they can be customized more than a standard service provider’s SBC, supporting multiple providers and platforms. However, E-SBCs typically require more management and overhead expense, and can be pretty complex. This is why it’s crucial to understand the business case and communication needs of the enterprise before investing in one strategy or the other.

In our next post, we will look at the state of the SBC and e-SBC markets and where they are headed.

Cahit Akin, CEO, Mushroom Networks, Inc. 

Mushroom Networks is the provider of SD-WAN (Software Defined WAN) and NFV solutions capable of Broadband Bonding that enables self-healing WAN networks that route around network problems such as latency, jitter and packet loss.


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