Redundancy & High Availability

High Availability Redundancy for All

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The Need for High Availability

The need for businesses to remain on-line at all times, if the connection to the service provider or on premise equipment should go down, is a critical one. And it is critical for all businesses, large and small alike.

In VoIP networking, the ability to always keep the network up and running is called High Availability (HA) and it can mean several things. For one, it means survivability. If the WAN connection (SIP trunk) to the service provider goes down, the customer needs a “Plan B”.  This is typically accomplished with a Session Border Controller (SBC) deployed at the enterprise, playing an important role in continued phone connectivity and routing at the customer site. It also can mean resilience. Here, the calls at the customer will find their way out of the local site to their destinations via alternative channels. This can be via PSTN fall-back, via GSM connection or even via a connection to a back-up second SIP trunk.

Redundancy & High AvailabilityAnd then there is redundancy where fully redundant networking infrastructure is used, eliminating single point of failure risks. With VoIP networking this would mean there are two SBCs deployed in an active/standby configuration. In normal operations, the first SBC does everything while the standby SBC is only synched with the first one. However, if for whatever reason the first SBC goes down, the second one takes over and all the active calls now go through it, ensuring that no active calls are dropped. User registration is synched between the two devices and a transfer to the standby SBC, seamless to both the network and to the users, occurs.

Increase in HA Demand for Medium to Small Businesses

Survivability and resiliency tend to be features provided in networks of all sizes. However, redundancy, for many vendors, seems to be reserved for only the larger carrier and enterprise networks, those with over 600 sessions. To handle requirements for High Availability redundancy for small to medium businesses some SBC vendors offer their customers over-sized carrier-class SBCs. This mismatch forces customers to deploy SBCs which don’t fit neatly into the enterprise environment, as they are more expensive, have unnecessary features on the one hand and may be missing other features necessary for this environment on the other.  (We call this “Going duck hunting with a Howitzer” – overly complex and in the end, not very effective).

At AudioCodes, we have witnessed a sharp increase in demand for High Availability Redundancy in small to medium businesses.  Perhaps these businesses have reached the conclusion that even in these smaller business environments they simply can’t take the risk that something will take down their network. AudioCodes has moved to satisfy this demand from the smaller businesses by installing High Availability redundancy in the Company’s Mediant 500 and 800 SBCs in addition to the higher-session SBCs.

(BTW: no ducks were harmed in the writing of this article)

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