The SIP Trunking Ensemble Needs a Conductor

By Acme Packet's Seamus Hourihan

Anyone with an appreciation for music knows that an ensemble of virtuoso musicians, even the most talented, will sound awful if the conductor fails to provide strong coordination among the musicians. Conversely, a collection of fair musicians can be lifted to the highest level with a talented conductor who knows how to get the most out of each individual.

Until recently, SIP trunking services have mostly been about a single instrument — voice. Now, SIP trunking providers are creating veritable ensembles, augmenting basic VoIP with a variety of overlay services. Services such as hosted PBX and UC, video and audio conferencing, and toll-free IP represent some of the additional “instruments” being added to the SIP trunking mix.

For enterprises, contact centers and government organizations, the benefits of this “ensemble” approach are evident:

• Reduced opex through use of a single SIP trunk for multiple applications rather than manage individual connections, IP or otherwise, for each service and application
• Reduced capex and opex through elimination of premise-located gateways
• Flexible location of service delivery elements — on-premise or in the service provider network
• Simpler introduction of new applications through re-use of an already-provisioned SIP trunk

Despite the benefits, getting all the instruments to play in harmony still poses numerous challenges. These include the ability to:

• Achieve seamless interoperability between enterprise-located infrastructure and the SIP trunking provider
• Guarantee quality of service for all applications running over the SIP trunk
• Ensure high availability for all of the services
• Provide comprehensive security for all services and applications (note: encryption and enterprise data firewalls are not the answer)
• Comply with local, state and federal regulations for emergency services, consumer protection, etc.
• Manage costs so the promised ROI is actually achieved

Overcoming these challenges is where the role of the conductor comes in, and that role can only be played by a session border controller (SBC) located at the customer premise. While SBCs deployed in the service provider network primarily protect services and service delivery infrastructure, premise-located enterprise SBCs play a much different role.

The enterprise SBC “orchestrates” the interoperability, quality of experience, service availability and appropriate controls required by customers simultaneously running business-critical functions such as customer service, HD telepresence and conference calls over SIP trunks. For example, SBCs:

• Normalize the signaling behaviors of enterprise-located IP PBXes and UC servers, matching it to the SIP profile mandated by the service provider
• Perform bandwidth-based admission controls, ensuring adequate bandwidth exists on the SIP trunk to support a given session for a given application before the INVITE is forwarded
• Proactively monitor the status of upstream routers and/or SIP session agents so that sessions can be re-routed in the event of a link or trunk-level failure

The best conductors must have full knowledge and awareness of all their musicians in order to impose appropriate control over each section of the orchestra. Similarly, the enterprise SBC is uniquely capable of asserting control by protecting itself, the enterprise service infrastructure and all IP-interactive communications from a wide variety of malicious and non-malicious attacks or threats.

The challenge of running multiple IP overlay services over SIP trunks is indeed analogous to conducting a musical ensemble. In its role applying the required control functions for these services, SBCs lead the ensemble (all services and applications), accommodate new instruments (such as HD VoIP and other next generation services) and scale as the ensemble eventually becomes a full orchestra, supporting multiple applications and sessions.

Seamus Hourihan, who first coined the term “session border control,” is the vice president of marketing and product management at Acme Packet. Seamushas driven industry recognition of the critical importance of the new product category created by Acme Packet.