The Slow Demise of Dedicated SIP Trunking & SBCs

by Sorell Slaymaker

Ten years ago, the big question was if NSPs would be “bit haulers” as everything becomes an Over The Top (OTT) application, or if they would be able to add value to services running on their network.  Video was the wildcard on whether it would go over the SIP network with voice, similar to ISDN.  The market is delivering video services as OTT, and voice will follow.  This, plus telephony will be bundled in with applications delivered by cloud service providers and less from the traditional phone companies.

Dedicated SIP trunking means carving out specific IP networks to just run voice traffic over.  Many inter-NSP and NSP to enterprise IP network connectivity was dedicated for VoIP/SIP traffic.  SBCs are used as a stateful demarcation point that delivers security, interoperability, and management. Dedicating infrastructure, both network and SBCs, for voice only traffic will fade away as voice becomes another OTT application.

Seven things are leading to the demise of dedicated SIP trunking & SBCs:

  1. Embedded Communication – Adding voice, video, and data natively within an application using WebRTC and/or communication APIs versus going to a separate application for communication
  2. Adaptive Codecs – Higher tolerance for network packet loss and jitter with royalty free adaptive codecs such as Opus and providing good communication over best effort Internet and Wifi networks.
  3. SD-WAN – Being able to monitor voice quality in real-time and route to another path if quality degrades along with the option of doing forward error correction
  4. Next Generation Firewalls – Firewalls that can provide application specific security including voice and video
  5. SIP Standardization – SIP inter-operability was a big challenge in the early adoption and migration to SIP trunking and migration away from H.323. This is no longer the case.
  6. Cloud – Cloud service providers are delivering more of the communication services as OTT service, and less voice is being delivered from the traditional NSP
  7. 5G Cellular – Even though 5G is a few years away, as it is rolled out, voice will delivered over IP and the business model of charging by the minute will fade away. (One of my favorite quotes “40% of the phone bill is the phone bill”.)

In North America, about 50% of large enterprises have migrated to SIP trunking, the rest are still on TDM or analog.  The majority of large enterprises implemented SIP trunking with a centralized architecture whereby all the voice trunks came into a couple of data centers and then the calls were passed over the enterprise WAN as depicted below.


Dedicated SIP trunking was an interim solution of moving voice from the TDM T1/PRI world to VoIP.  Because VoIP is a critical application and VoIP’s intolerance to poor network performance, a dedicated network was used within NSP and NSP to enterprise connections.

The migration off of TDM and analog will continue, the only change is that there are alternative ways on delivering voice versus dedicating infrastructure specific for voice traffic.  Every technology has a lifecycle, just like Plane Old Telephone Service (POTS) delivered over analog lines.  SIP itself is not going away anytime soon, just the need to dedicated infrastructure specifically for voice traffic.