This clause provides functional descriptions of capabilities in GGSN. The capabilities are part of IP BS Manager (see clause 184.108.40.206
) or corresponding user plane functions. Determination of exactly which functions are required to support interoperator and multi-vendor aspects are not addressed in this clause.
The DiffServ Edge Function
shall be compliant to the IETF specifications for Differentiated Services (RFC 2475
). The IETF Differentiated Services architecture will be used to provide QoS for the external bearer service.
Parameters for the DiffServ Edge Function (i.e. classifiers, meters, packet handling actions) may be statically configured on the GGSN, derived from PDP Context parameters and/or derived from RSVP signalling.
DiffServ functions configured on the basis of PDP Context parameters consist of marking user packets. The DSCP to be used is derived from the PDP Context parameters according to statically configured rules.
Statically configured DiffServ functions may include classifiers, meters, markers, droppers and shapers acting on uplink traffic.
Policy and Charging Enforcement Function (PCEF)
controls the user plane quality of service that is provided including policy-based admission control that is applied to the bearer and gating control. Policy decisions are either pushed to or requested by the GGSN via the Gx interface.
Policy-based admission control ensures that the resources that can be used by a particular set of IP flows are within the "authorized resources" specified via the Gx interface. The authorized resources provide an upper bound on the resources that can be reserved or allocated for the set of IP flows.
The authorized resources are expressed as a maximum authorized bandwidth and QoS class. The QoS class identifies a bearer service (which has a set of bearer service characteristics associated with it). The PCRF generates a maximum authorized QoS class for the set of IP flows. This information is mapped by the translation/mapping function in the GGSN to give the authorized resources for UMTS bearer admission control.
In the user plane, policy enforcement for an individual or a set of IP flows is defined in terms of a "gate" implemented in the GGSN. A gate is part of the policy enforcement functionality and is controlled by the PCRF through Gx interface signalling. A gate consists of a packet classifier, and a gate status (open/closed). When a gate is open, the packets matching the packet classifier are accepted, and are thus subject to the DiffServ edge treatment in uplink direction or forwarded in their corresponding PDP context in downlink direction. When a gate is closed, all of the packets matching the packet classifier are dropped.