Optimizing Basic Telephony on Your UC Platform – Part 2

July 9, 2019

Keith Bareham, Director Solutions Engineering, VOSS Solutions

In Part 1 of this blog post, we considered the cases where advanced Cisco UC platforms may not provide the most cost effective solution at the lower end of the telephony feature set. In Part 2, we take a look at our solution to this challenge.

VOSS Call Flow Optimization extends the Cisco UC and HCS platforms by taking the minimum components required for basic telephony and providing these services via adjunct VOSS telephony servers placed in the customer network. These servers may be deployed in multiples to provide both capacity and redundancy and are used provide services alongside the usual CUCM and CUC servers. The services provided by the Call Flow Optimization servers are:

• Registrar capability to allow SIP device registration – A SIP registrar allows per-line registration from suitably configured devices. When configured with the correct credentials, a device such as a phone is able to register with the registrar, providing the network attachment required in order to route calls to the phone.
• SIP switching to allow call handling – This simply processes calls between registered devices and to the rest of the HCS estate. PSTN break in and break out are also catered for.
• Device configuration management – In order to manage large volumes of phones, centralised configuration management is required. This allows phones to be deployed without the need to locally configure the phone itself. Many of the user functions are provided by the phone itself, and this configuration is managed via VOSS-4-UC.
• Call routing – Call Flow Optimization uses the CUCM dial plan and trunks to provide routing to and from the PSTN via existing aggregation trunks. When new phones are added to Call Flow Optimization, dial plan is added to CUCM to route calls from CUCM to the new Call Flow Optimization extension number. Existing Cisco UC and HCS functions such as E164 mapping for inbound calls are retained.

These basic functions are provided using the VOSS Call Flow Optimization server placed in the customer network. The Call Flow Optimization server is an API-driven adjunct providing these services to telephony users rather than a PBX. The presentation of the service is provided through VOSS-4-UC, where the concepts of phones, number inventory and sites are used in the same way as used in ordinary Cisco UC deployments. It is only when an administrator requests service that these underlying functions are then managed invisibly to the user via APIs.

When creating a customer who may use Call Flow Optimization, the customer is provisioned in the usual way in VOSS-4-UC, up to the point of configuring phones. This includes dial plan and number inventory management. Cisco UC and HCS-hosted phones are added in the usual way and may be mixed with Call Flow Optimization devices. A new menu item allows adding Call Flow Optimization hosted phones. Adding a Call Flow Optimization phone automates the configuration of the functions described above:

• The registrar function is configured using the Call Flow Optimization APIs in preparation for phone registration
• The phone configuration files are prepared and made available on the Call Flow Optimization server for the phone to download as it boot
• APIs are used to create the configuration file based on a template file
• Call Flow Optimization currently supports XML formatted configuration files which can be served to phones from various vendors
• CUCM call routing is added to allow routing of the new directory numbers to the Call Flow Optimization server

In addition to these configuration steps, the number inventory is marked accordingly and made unavailable for use by CUCM hosted devices.

By bringing together a simplified implementation of basic calling services, the existing Cisco UC or HCS platforms are extended to provide a hybrid of fully featured unified communications alongside basic telephony in cases where customer profiles demand such a service.

If you would like to talk to VOSS about solving your company’s challenges around optimising your UC platform and reducing costs associated with delivering basic telephony, please contact us.