This clause provides functional descriptions of capabilities in GGSN. The capabilities are part of IP BS Manager (see clause 18.104.22.168
) 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.
This clause provides functional descriptions of capabilities in UE. The capabilities are part of IP BS Manager (see 22.214.171.124) 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.
DiffServ Edge Function
acts as a DiffServ (DS) boundary for the traffic from applications running on the UE. As specified in RFC 2475
, DS boundary node must be able to apply the appropriate PHB to packets based on the DS code point. In addition, DS boundary nodes may be required to perform traffic conditioning functions. When GGSN DiffServ marking is used, the DiffServ edge function in the UE is not needed.
provides the capability for the UE to request end-to-end QoS using RSVP messages as defined in IETF standards. RSVP messages may also be used by the network to inform the DSCP to be used by the UE. RSVP messages shall include the authorization token and flow identifier(s) in a policy data object if the authorization token is available in the UE. RSVP may be used to trigger PDP context activation/modification. The inter-working between MT and TE is FFS.
This clause provides high level functional descriptions of PCRF capabilities. The PCRF makes policy decisions, e.g. based on policy set-up information obtained from the AF via the Rx interface.
The PCRF checks that if the policy set-up information received from the AF is consistent with operator policies defined in the PCRF.
The PCRF authorizes QoS resources (bandwidth, etc.) for the AF session. The PCRF uses the policy set-up information received from the AF to calculate the proper authorization. The authorization includes the limits on QoS for the set of IP flows and restrictions on individual IP flows (e.g. destination address and port).
The PCRF decides if new QoS authorization (bandwidth, etc.) is needed due to a mid-call media or codec change. The PCRF re-authorizes QoS resources when the resources requested by the UE for a flow exceeds previous authorization, or a new flow is added, or when elements of the packet classifier(s) for authorized flows change.
The PCRF provides the policy decision information to the GGSN via the Gx interface.
The PCRF provides gating control decisions controlling the gate for the authorized media stream.
At AF session release, the PCRF revokes the QoS resource authorization for the AF session.
For further details, see TS 23.203
The Application Function (AF) is an element offering applications that require the control of IP bearer resources (e.g. UMTS PS domain/GPRS domain resources). One example of an Application Function is the P-CSCF in the IMS architecture.
Policy control related functions
The AF uses the Rx interface to exchange service based policy set-up information with the PCRF. This applies both during session establishment, as well as upon a mid-session modification affecting the media (e.g. addition of a new media in mid-session).
The AF may give instructions to the PCRF defining how the PCRF shall interact with the PCEF for certain events related to policy control. The AF is able to give instructions to the PCRF to act on its own, i.e. based on the service information currently available, for the following events:
The authorization of QoS resources for the AF session;
The gate control (i.e. whether there is a common gate handling per AF session or an individual gate handling per AF session component required);
The forwarding of transmission resource level events.
For further details, see TS 23.203