This Recommendation provides the stage 3 specification of the protocol at the interface between
service control entities (SCE) and the policy decision physical entity (PD-PE). The functional
requirements and the stage 2 specifications for this interface are contained in clause 8.1 of
[ITU-T Y.2111] and in [ITU-T Q.Sup 51]. This interface is used to control session-based policy.
Using the protocol specified in this Recommendation, the SCE can:
• provide information to the PD-PE to identify media flows and their required QoS resource
characteristics (e.g., QoS class, bandwidth, priority);
• provide service priority information to the PD-PE to facilitate appropriate priority handling;
• request resource usage information through the PD-PE for charging;
• provide related service information to the PD-PE to facilitate appropriate dynamic firewall
working mode selection;
• indicate whether the media should be enabled (i.e., gate opened) when resources are
reserved;
• in those instances where the media should not be enabled as soon as the resources are
reserved, i.e., may request that the gate be opened later;
• in the case where a NAPT function is required, request address mapping information so it
can do any modifications that may be required to address information within application
signalling (e.g., SDP); and
• in the case where a path-coupled resource reservation mechanism is used, indicate to the
PD-PE whether it wishes to be notified when reservations are obtained and released.
When an authorization token mechanism is used, the PD-PE may supply the SCE with one or more
authorization tokens which the SCE shall include in application signalling to the CPE.