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Protocols for Rules Management on the TDF Sd Reference Point


The following two types of protocols are available on the Sd interfaces for TDF. Currently, Sd interfaces are supported on the Services Control Gateway.

Sd Application as the Only 3GPP Specified Protocol

In 3GPP specifications, the reference point between a PCRF and a TDF is the Sd reference point. The protocols supported , according to 3GPP specification, over the Sd reference point is the Sd application (specified since 3GPP Release 11) , which supports two operating modes:

  • Solicited reporting mode, where the Sd session is initiated by the PCRF to the TDF (and which supports, according to the 3GPP specs, dynamic ADC controls)

  • Unsolicited reporting mode, where the Sd session is initiated by the TDF (which according to standard specifications, does not support any QoS controls or dynamic ADC rules)

On a standalone TDF there are no other standards-compliant protocols to manage policy rules; note also that a TDF, according to the specifications, is not expected to manage rules at Layer 4 (for example, dynamic PCC rules). Using Sd application (which has a specific Diameter application ID), the PCRF can manage only the ADC rules according to the specifications.

Sd Reference Point with a Non-Standard Use of Gx Over Sd Reference Point

The specifications indicate that a PCEF (so a GGSN/PGW element) can support, using Gx Rel 11 protocol, both PCC and ADC controls. The functional scope of Gx on a PCEF is much broader than the extent or capabilities that are required on a TDF (as all the bearer binding functionality is not required in a TDF). However the initial requirement for the TDF is to support a subset of Gx protocol capabilities to provide both PCC and ADC controls (from Layer 4 to Layer 7) on a standalone TDF. This use of a subset of a Gx protocol specification between PCRF and TDF is not specified in any 3GPP Specification as of today. However, this usage is a de-facto best practice across many vendors performing application level controls through PCRF (for example, video optimizations and DPI vendors).

The following table provides a summary of the requirements for TDF in terms of protocols being used over Sd reference point versus types of rules to be managed on the TDF.

Type of Rules Protocol over Sd

Standard PCC Rules

Standard ADC Rules

PCC rules enhanced with ADC AVPs

Subset of Gx protocol

PCC using Gx mode

Non standard use of Gx between PCRF and TDF

Standard PCC rules (preconfigured and dynamic)

Non standard use of Gx between PCRF and TDF

Standard ADC rules are not supported.

ePCC using Gx mode Non standard use of Gx between PCRF and TDF Non standard PCC rules (PCC rules containing TDF-Application-Id and Redirect AVPs; preconfigured and dynamic)

The following table summarizes supported protocol and rules, and the name of the associated mode of operation of the TDF:

Mode of operation

Protocol used over Sd reference point

Type of policy rules managed

PCC rules using Gx (mode 1)

Subset of Standard Gx

Standard PCC rules (only Layer 4 control, when only dynamic rules are used)

ePCC rules using Gx (mode 2)

Standard Gx adding Application-Detection specific AVPs or values such as App-Start, App-Stop

ePCC rules= PCC rules with App-Detection-Information AVP and Redirect-AVPs

ADC rules using Sd solicited (mode 3), ADC rules using Sd enhanced unsolicited (mode 4) modes are currently not supported for managing ADC rules. Similarly, ePCC rules using Sd solicited (mode 5) and ePCC rules using Sd enhanced unsolicited (mode 6) for managing ePCC rules are not currently supported. These modes of operations of TDF might be implemented in a future release.