Business Continuity with the Session Border Controller

Most enterprises think of installing the Enterprise Session Border Controller (E-SBC) for several reasons but not for business continuity. The primary goals of the SBC are protection from network invasion and for security. It is also implemented for transcoding, translating streams of signaling and speech for connection to SIP trunks. The E-SBC can be configured to enhance the network survivability of a location when connected to SIP trunks. 

A value of the E-SBC is that it can connect to multiple IP PBXs or IP phone LANs or gateways to multiple SIP trunk providers. This is a capability normally associated with large communications sites. The common E-SBC can have 8 or more Ethernet ports, arranged as pairs for redundancy, which can be assigned in many configurations.

The E-SBC's physical Ethernet ports can be grouped into pairs where each pair group consists of an active port and a standby port. This provides Ethernet port redundancy within a group. If an active port is disabled, the E-SBC switches over to the standby port. This enables physical separation of network interfaces, providing a higher level of segregation of sub-networks. 

Two ports in a group can be configured to connect to the primary and backup IP PBX servers on separate LANs. If one server/LAN combination fails, the E-SBC can detect the failure and switch to the backup port in the group.

Another Ethernet port group can be assigned to different SIP trunk providers. One group can be connected to a single WAN. The WAN connection can be logically assigned to multiple SIP trunk providers. An alternative configuration can support multiple WAN connections to a single SIP trunk provider or to multiple SIP trunk providers.

These trunk connections can share the load during peak traffic situations. If one SIP trunk provider fails, the E-SBC can detect the failure and route all the traffic to the operating SIP trunk. Outside the busy hour of traffic and one trunk provider fails, it is likely that the other trunk provider can carry the traffic load. 

A second advantage of two or more SIP trunk providers is that they are forced to compete for the enterprise business. The enterprise can always threaten to cancel one of the providers if the audio quality is poor and/or unreliable. This ensures that the trunk providers have an incentive to provide acceptable support.  The E-SBC has internally generated reports to measure the effectiveness of each of the SIP trunk providers delivering an unbiased comparison of the multiple SIP trunk providers performance.

An additional business continuity capability is configuring a VoIP gateway connected to the PSTN and E-SBC. This offers local call backup connections to the PSTN if the SIP trunks are no longer usable. The IP phones connected to the E-SBC can establish calls through the gateway to the PSTN ensuring that calls will be completed, especially in emergency situations.

There is also the possibility that an E-SBC may fail. Some E-SBC vendors offer a discount, as much as 50% when a second E-SBC is configured as a backup. The E-SBCs can support a keep alive function between them so when one fails the other can switch in to carry the entire traffic load. It is probably a good idea, with a pair of E-SBCs, to have them share the traffic load rather than operate one as the primary and the second as a standby backup. This further reduces the chances that there will be an interruption to the traffic flow when a switchover occurs.

The capabilities mentioned above have been a part of the larger E-SBC products for location at data centers. These capabilities are now offered in smaller E-SBCs, those that would be implemented in branch offices. The branch office versions are also candidates for the SMB data centers.

Business continuity is one of many advantages of the E-SBC. Look for other features that usually come standard with the E-SBC. The business continuity capabilities and these other extra features will help in the financial justification of the E-SBC.

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