Can a Policy Controller also do SDN and Charging?

Can a Policy Controller also do SDN and Charging?

Last week at the LTE MENA conference a vendor was showing their SDN proposition for mobile operators. They depicted in their slides the policy controller (PCRF) cooperating with the SDN controller for service function chaining.

I was only relatively surprised because this vendor policy product is known to come from a charging background and I wonder how challenging has to be to try to do the three things: Poilcy, Charging and SDN. It made me think.

I started working with policy control in 2007 (with this, demonstrated here). At that time, policy was about communicating between applications (namely the IMS) and network (the GGSN at that time). The IMS wanted to tell the network that a “multimedia” session was starting and the policy controller required to reserve some network resources, apply some packet marking to the IP packets that carry the media etc. I was explaining people that policy was actually about bridging between application and network.

Next  DPIs become popular and policy was more about activating throttling for unwanted applications. Policy turned Police. My view was that policy was actually judge,  deciding which rules to apply to a certain user understanding their context.

Then Usage Monitoring became a feature of the PCRF and it started controlling how much the users consume and throttling them when they reached their limits. The overlap with the Online Charging System (OCS) was significant. Many PCRF vendors today actually come from a charging background. Very late, 3GPP decided to create a standard interface for the PCRF to cooperate with the OCS. This interface, Sy, is not being widely used and many operators see simpler to have a co-located PCRF and OCS from the same vendor.

Apparently everything happens in cycles and in the last two years with VoLTE the PCRF has recovered the bridging functionality.

Now we have SDN coming into picture; although at the moment of writing my report about NFV/SDN (here)  I was more skeptical about the overlap between Policy and SDN Control know that I am researching more the topic I am more convinced about it.

The SDN Controller is also bridging between applications needs and network resources. While the PCRF does it for end user applications the SDN Controller offers it also for virtual network functions and the orchestrator which is establishing services. The difference is that the SDN Controller will have a much broader knowledge of the network topology and resource availability while the PCRF understands better the context and needs of the user by being subscriber