what is difference between TDF and PCEF?

Question

In the PCC architecture there is is TDF and PCEF that they are same. What is difference between TDF and PCEF? HowTDF and PCEF work with together?

Answer 1

Firstly it is worth also mentioning the PCRF, the Policy and Charging Rules Function, which is the entity that defines and manages the policies. It will often group sets of rules into profiles.

The TDF, Traffic Detection Function, is 'is a functional entity that performs application detection and reporting of detected application and its service data flow description to the PCRF'.

The PCEF 'encompasses service data flow detection, policy enforcement and flow based charging functionalities.'

From the above descriptions, all from the 3GPP spec the distinction seem quite clear - the PCRF is the brains, the TDF detects application flow and the PCEF enforces policy. However, the TDF definition goes on to say that a TDF:

For solicited application reporting, the PCRF can request the TDF to also perform enforcement actions and usage monitoring. For those cases where service data flow description is not possible to be provided by the TDF to the PCRF, the TDF performs:

• Gating;
• Redirection;
• Bandwidth limitation. for the detected applications.

and to also note that a PCEF can be extended to include TDF functionality:

NOTE: The PCEF can be enhanced with application detection and control feature as specified in clause 6.2.2.5

So, your question is a good one, there is clearly some potential for overlap, and it is quite common for vendors to actually offer a single combined TDF/PCEF product.