1. Policy and Charging in
Telecom Networks
Inam Ullah
Director Product Development
EMI Networks
2. Agenda
• What is Policy Control
• Why Policy Control in EPC/SAE/LTE?
• Business Requirements for Policy & Charging
Control
• Policy Charging and Rule Function(PCRF)
• Policy in 2G/3G networks
• Migration to IMS & EPC
• Policy and Charging Control in 3GPP Network
• Conclusion
3. What is a Policy Control?
Process of Defining and Enforcing
configurable business rules to
enable wide range of intelligent,
real-time controls, quality of service
(QoS) changes, optimizing high
bandwidth traffic, and enforcing
usage quotas.
4. Levels of Policy Control
• Local Policy
Local Policy is defined and administered at the entity which enforces it.
For example, both QoS and Charging Local Policy may be defined at PDSN.
Generally, these policies will have broad system wide applications.
• Static Policy
Static Policy is defined on a per subscriber basis and stored on a Static
Policy Server. Static Policy can be defined for both QoS as well Charging. It
is downloaded into PDSN where it is enforced.
• Dynamic Policy
Dynamic Policy is defined on a per application per session basis. It is
determined by a combination of information stored at Policy Decision
Function (PDF), the information provided by the subscriber during a
session initiation and the application itself. It is provided by PDF to PDSN
(PEF) during a session and enforced by PDSN.
5. Why Policy Control?
Business requirements as how services are delivered endto-end in accordance to subscriber preferences, service
agreement and network consideration covering:
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Authorization / Denial
Charging Rule
Quality of Service (e.g. Priority, Latency, Class, Route)
Dialogue Redirection
Bandwidth & Resource Allocation (e.g. Allocated, Shaping
and Throttling)
– Quota Rules
– Routing & Location Sensitive
– Monitoring & Service Triggers
6. Policy Control
• Policy control comprises functionalities for:
– Binding, i.e. the generation of an association between a service data
flow and the IP-CAN bearer transporting that service data flow;
– Gating control, i.e. the blocking or allowing of packets, belonging to a
service data flow or specified by an Application Identifier, to pass
through to the desired endpoint;
– Event reporting, i.e. the notification of and reaction to application
events to trigger new behaviour in the user plane as well as the
reporting of events related to the resources in the GW(PCEF);
– QoS control, i.e. the authorisation and enforcement of the maximum
QoS that is authorised for a service data flow, an Application identified
by Application Identifier or an IP-CAN bearer;
– Redirection, i.e. the steering of packets, belonging to an application
defined by the Application Identifier to the specified redirection
address;
– IP-CAN bearer establishment for IP-CANs that support network
initiated procedures for IP-CAN bearer establishment.
7. Business Drivers for PCC
Police subscribers and service agreements to a
subscriber-level and subscriber-group level for the
following mobile internet and broadband business
models including:
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Service Quota & Bandwidth Caps
Subscriber Overage Throttling and Termination (including EU Bill Shock)
Fair Usage Control
Parental Control
Time-Based, Usage and Location Based Charging / Tariff Switching
Voice, Video and Application QoS Setting, Bandwidth Allocation and Prioritization
On-Demand Bandwidth Turbo-Button Like functions
VIP Profile and Spend based prioritization and charging (e.g. Business Class, Pre-paid
vs. Post-paid vs. On-demand)
– Partner Service Priorities (e.g. official public internet VoIP)
– Peak Time Video and P2P Management
– Automated Service Advisory, Up-sell and Cross-sell
9. 3GPP Policy and Charging Control
• The 3GPP PCC functions include:
• PCRF (policy and charging rules function) provides policy
control and flow based charging control decisions.
• PCEF (policy and charging enforcement function)
implemented in the serving gateway, this enforces gating
and QoS for individual IP flows on the behalf of the PCRF.
It also provides usage measurement to support charging
• OCS (online charging system) provides credit
management and grants credit to the PCEF based on time,
traffic volume or chargeable events.
• OFCS (off-line charging system) receives events from the
PCEF and generates charging data records (CDRs) for the
billing system.
11. Policy Charging and Rule
Function(PCRF)
• The PCRF interfaces with the main packet gateway and takes charging
enforcement decisions on its behalf.
• Dedicated policy equipment standardized in 3GPP that enables the
policy function for bandwidth and charging on multimedia networks.
• The PCRF function is part of the larger PCC architecture, which also
includes the Proxy Call Session Control Function (P-CSCF) and the Policy
and Charging Enforcement Function (PCEF).
• Combined, the elements of the PCC provide access, resource, and
quality-of-service (QoS) control.
• PCRF is an important part of IMS architectures, although it is not
exclusive to the 3GPP-based network in which it was certified. It works
across wireless networks and can come pre-integrated in a standard IT
server.
• PCRF is often referred to as policy server or -- formerly -- a Policy
Decision Function (PDF).
12. Policy in Action: Video Streaming
Example
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customer has requested a streaming video that will
be paid for by the included advertising.
We will assume the customer likes the video and
decides after five minutes to pay for a higher data
rate with no advertising from her pre-paid video
account.
This requires specific QoS treatment to the
requested and modified by the streaming video
controller during the session.
It does this by appearing as an application function
to the PCRF. The PCRF and PCEF work together to
ensure the correct QoS is provided.
The charging aspects are managed by the OCS.
When the customer switches to the non-advertising
stream the PCEF will request credit from the OCS.
The OCS will check the customer’s video balance
and provide the appropriate credit for the IP flow.
The OCS has the job of correlating charging events
to ensure the customer is not charged for the data
stream, but only the video.
This sufficiently powerful to provide dynamic control
of charging and QoS on a per flow and per
subscriber basis.
13. Policy in 2G/3G networks
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Policy control, charging and billing
mediation are already complex functions.
IN pre-paid platform: originally deployed
to provide simple pre-paid voice services,
has been continuously extended to include
roaming, messaging, data and content
services to pre-paid customers.
Active mediation platforms: have been
deployed as adjunct platforms to the IN
pre-paid platform to support control and
usage measurement for messaging, data
and contents services.
Complex real-time rating platforms: have
been deployed as adjunct platforms to the
IN pre-paid platform to support more
complex tariff models and subscriber
models.
Policy control is already implemented to
support existing data services. This
includes some PCRF type functionality, but
not the full dynamic control of policy that
the EPC will provide.
GGSN and dedicated deep packet
inspection (DPI) platforms support active
mediation by enabling very detailed usage
measurements and control of IP flows.
14. Migration path from IMS LTE
• This real-time infrastructure is being integrated with offline billing to support
a hybrid model; where a customer can choose to have individual services
billed on a pre-paid or post-paid basis.
• The fundamental issue operators will face is how this already complex policy
control, charging and billing infrastructure will evolve to accommodate the
needs of LTE.
• A migration path is required from the legacy environment shown previously
to include the LTE/SAE architecture .
• The growth in transaction rates that the PCC will be required to support will
drive the replacement of most legacy components during the migration.
• The IN pre-paid platform in particular will be gradually eliminated as balance
management migrates to the online billing platform and the circuit switched
infrastructure is eventually replaced.
15. Policy in IMS Networks
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VoIP delivered over LTE will require the full
dynamic QoS controls standardized in the EPC.
To ensure appropriate QoS for voice calls and
use a similar mechanism to the video
streaming example
The PCRF capability should be the focus for any
enhancements to policy control.
Implementation on the PCRF enables policy
control to be used for both pre-paid, post-paid
and hybrid billing.
IP network for transport, signaling and control
based on IMS, EPC and LTE standards
There is likely to be a proliferation of
application and content servers that will use
the AF to manage quality of service and
charging requirements. T
This will generate a much higher load on the
policy and charging control platform. Operators
should factor in the scalability requirements of
these future needs when selecting solutions to
the current data only scenario.
16. PCRF requirements for LTE
• Active mediation systems and complex real-time rating adjuncts must evolve
to support the requirements of the 3GPP to find OCS.
• Rapidly growing usage will put a significant load on the systems and they will
need to be scaled accordingly.
• The migration of functionality away from legacy IN pre-paid platforms will
continue. Operators are already moving in this direction to support more
complex hierarchical accounts and enable subscribers to choose how individual
services are charged (pre-paid or post-paid).
• The PCRF capability should be the focus for any enhancements to policy
control. Implementation on the PCRF enables policy control to be used for
both pre-paid, post-paid and hybrid billing.
• Existing billing mediation platforms will need to be extended to support the
EPC elements. With rapidly increased data traffic these will need significant
scaling to meet demand.
• Existing off-line post-paid billing systems are complex and expensive to
upgrade. Where possible operators should insulate billing systems from the
changes in the network by focusing on enhancements to the PCC.
20. 3GPP Policy Control Architecture
Sp
Subscription Profile
Repository
(SPR)
AF
Online Charging
System
(OCS)
Rx
Policy and Charging Rules Function
(PCRF)
Sy
Gxx
Sd
Gx
Gy
BBERF
TDF
PCEF
PCEF
Gz
Gateway
Offline
Charging
System
(OFCS)
21. Functional Elements of PCC
Architecture
The PCC functionality is comprised by the functions of the
• Policy and Charging Enforcement Function (PCEF)
• Bearer Binding and Event Reporting Function (BBERF)
• Policy and Charging Rules Function (PCRF)
• Application Function (AF)
• Traffic Detection Function (TDF)
• Online Charging System (OCS)
• Offline Charging System (OFCS)
• Subscription Profile Repository (SPR) or the User Data
Repository (UDR)
22. Policy Control and Charging Rules
Function (PCRF)
• The PCRF encompasses policy control decision and flow based
charging control functionalities.
• The PCRF provides network control regarding the service data
flow detection, gating, QoS and flow based charging (except
credit management) towards the PCEF.
• The PCRF shall apply the security procedures, as required by the
operator, before accepting service information from the AF.
• The PCRF shall decide whether application traffic detection is
applicable, as per operator policies, based on user profile
configuration, received within subscription information.
• The PCRF shall decide how certain service data flow/detected
application traffic shall be treated in the PCEF and in the TDF, if
applicable, and ensure that the PCEF user plane traffic mapping
and treatment is in accordance with the user's subscription
profile.
23. Policy and Charging Enforcement
Function (PCEF)
• The PCEF encompasses service data flow detection, policy
enforcement and flow based charging functionalities.
• This functional entity is located at the Gateway (e.g.
GGSN in the GPRS case, and PDG in the WLAN case). It
provides service data flow detection, user plane traffic
handling, triggering control plane session management
(where the IP-CAN permits), QoS handling, and service
data flow measurement as well as online and offline
charging interactions.
• A PCEF shall ensure that an IP packet, which is discarded
at the PCEF as a result from policy enforcement or flow
based charging, is neither reported for offline charging
nor cause credit consumption for online charging.
24. Application Function (AF)
• The Application Function (AF) is an element offering applications
that require dynamic policy and/or charging control over the
IP-CAN user plane behaviour.
• The AF shall communicate with the PCRF to transfer dynamic
session information, required for PCRF decisions as well as to
receive IP-CAN specific information and notifications about IP-CAN
bearer level events.
• One example of an AF is the P-CSCF of the IM CN subsystem.
• The AF may receive an indication that the service information is
not accepted by the PCRF together with service information that
the PCRF would accept. In that case, the AF rejects the service
establishment towards the UE.
• If possible the AF forwards the service information to the UE that
the PCRF would accept.
25. Traffic Detection Function
• The TDF is a functional entity that performs
application detection and reporting of detected
application and its service data flow description to
the PCRF.
• 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.
26. Subscription Profile Repository
(SPR)
• The SPR logical entity contains all subscriber/subscription related
information needed for subscription-based policies and IP-CAN bearer
level PCC rules by the PCRF.
– Subscriber's allowed services;
– For each allowed service, a pre-emption priority;
– Information on subscriber's allowed QoS, including the Subscribed
Guaranteed Bandwidth QoS;
– Subscriber's charging related information (e.g. location information relevant
for charging);
– Subscriber's User CSG Information reporting rules;
– Subscriber category;
– Subscriber's usage monitoring related information;
– MPS EPS Priority and MPS Priority Level;
– IMS Signalling Priority;
– Subscriber's profile configuration indicating whether application detection
and control should be enabled.
– Spending limits profile containing an indication that policy decisions are
based on policy counters available at OCS that has a spending limit
associated with it and optionally the list of policy counters.
29. Bearer Binding and Event
Reporting Function (BBERF)
• The BBERF includes the following functionalities:
– Bearer binding.
– Uplink bearer binding verification.
– Event reporting to the PCRF.
– Sending or receiving IP-CAN-specific parameters, to
or from the PCRF.
30. Policy and charging control rule
• The Policy and charging control rule (PCC rule) comprises the
information that is required to enable the user plane detection of, the
policy control and proper charging for a service data flow. The packets
detected by applying the service data flow template of a PCC rule are
designated a service data flow.
• Two different types of PCC rules exist: Dynamic rules and predefined
rules. The dynamic PCC rules are provisioned by the PCRF via the Gx
reference point, while the predefined PCC rules are directly provisioned
into the PCEF and only referenced by the PCRF. The usage of pre-defined
PCC rules for QoS control is possible if the BBF remains in the PCEF
during the lifetime of an IP-CAN session. In addition, pre-defined PCC
rules may be used in a non-roaming situation and if it can be guaranteed
that corresponding pre-defined QoS rules are configured in the BBF and
activated along with the pre-defined PCC rules.
32. Rx reference point
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The Rx reference point resides between the AF and the PCRF.
This reference point enables transport of application level session information from
AF to PCRF. Such information includes, but is not limited to:
– IP filter information to identify the service data flow for policy control and/or differentiated
charging;
– Media/application bandwidth requirements for QoS control.
– In addition, for sponsored data connectivity:
– the sponsor's identification,
– optionally, a usage threshold and whether the PCRF reports these events to the AF,
– information identifying the application service provider and application (e.g. SDFs, Application ID,
etc.).
•
The Rx reference point enables the AF subscription to notifications on IP-CAN bearer
level events (e.g. signalling path status of AF session) in the IP-CAN.
33. Gx reference point
• The Gx reference point resides between the PCEF and the PCRF.
• The Gx reference point enables a PCRF to have dynamic control over
the PCC behaviour at a PCEF.
• The Gx reference point enables the signalling of PCC decision, which
governs the PCC behaviour, and it supports the following functions:
– Request for PCC decision from PCEF to PCRF;
– Provision of IP flow mobility routing information from PCEF to PCRF; this
applies only when IP flow mobility as defined in TS 23.261 [23] is supported;
– Provision of PCC decision from PCRF to PCEF;
– Reporting of the start and the stop of a detected applications and transfer of service data flow
descriptions for detected applications, if available, from the PCEF to the PCRF;
– Delivery of IP-CAN-specific parameters from PCRF to PCEF or from PCEF to PCRF; this applies only
when Gxx is deployed.
– Negotiation of IP-CAN bearer establishment mode (UE-only or UE/NW);
– Termination of Gx session (corresponding to an IP-CAN session) by PCEF or PCRF.
34. Subscriber Databases
• Sp reference point
• The Sp reference point lies between the SPR and the PCRF.
• The Sp reference point allows the PCRF to request subscription
information related to the IP-CAN transport level policies from the SPR
based on a subscriber ID, a PDN identifier and possible further IP-CAN
session attributes, see Annex A and Annex D. For example, the
subscriber ID can be IMSI. The reference point allows the SPR to notify
the PCRF when the subscription information has been changed if the
PCRF has requested such notifications. The SPR shall stop sending the
updated subscription information when a cancellation notification
request has been received from the PCRF.
• Ud reference point
• The Ud reference point resides between the UDR and the PCRF, acting
as an Application Frontend as defined in TS 23.335 [25]. It is used by the
PCRF to access PCC related subscription data when stored in the UDR.
35. Gy reference point
• The Gy reference point resides between the OCS
and the PCEF.
• The Gy reference point allows online credit
control for service data flow based charging
• Gy reference point are defined in TS 32.251
36. Gz reference point
• The Gz reference point resides between the PCEF
and the OFCS.
• The Gz reference point enables transport of
service data flow based offline charging
information.
• The Gz interface is specified in TS 32.240
37. Sd reference point
• The Sd reference point resides between the PCRF and the TDF.
• The Sd reference point enables a PCRF to have dynamic control
over the application detection and control behaviour at a TDF.
• The Sd reference point enables the communication between
TDF and PCRF for the purpose of:
– Establishment of TDF session between PCRF and TDF;
– Termination of TDF session between PCRF and TDF;
– Provision of Application Detection and Control decision from the
PCRF for the purpose of traffic detection and enforcement at the
TDF;
– Reporting of the start and the stop of a detected applications and
transfer of service data flow descriptions for detected applications,
if deducible, from the TDF to the PCRF,
38. Sy reference point
• The Sy reference point resides between the PCRF and the OCS.
• The Sy reference point enables transfer of information relating
to subscriber spending from OCS to PCRF and supports the
following functions:
• - Request of charging status reporting from PCRF to OCS.
• - Notification of policy counter status change from OCS to
PCRF.
• - Cancellation of charging status reporting from PCRF to
OCS.
• Since the Sy reference point resides between the PCRF and
OCS in the HPLMN, roaming with home routed or visited
access as well as non-roaming scenarios are supported in the
same manner.
39. Conclusion
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The end user experience, with the appropriate charging and billing infrastructure, can
be translated into increased revenue and customer loyalty.
PCC capabilities will be an enabler for new differentiated services and new business
models. Moving beyond a simple flat rate to offering customers the choice of
bandwidth, QoS, advertising funded services and the like will be important in
monetizing the LTE investment.
LTE/SAE supported data services can deliver significant new value to the end customer
with increased bandwidth, reduced latency and fine-grained control over QoS. The
value can only be realized by flexible charging, policy management and billing solutions.
The ability to rapidly deploy new charging models and integrate QoS policies will be
critical to competing and succeeding with LTE. Operators must include these
requirements in their LTE/SAE rollout plan.
Billing systems have proved to be costly and time-consuming to upgrade. Operators
can minimize the impact of this by using the mediation and charging platforms to hide
major changes from the billing system. These tend to be more modern platforms and
therefore less costly to upgrade.
40. Conclusion
• Providing voice over LTE with IMS support for rich communication
services can add significant value to the services offered.
• Deployment of more powerful DPI capabilities, either standalone or as
part of the PDN gateway will be important in supporting some of the
more sophisticated new service opportunities.
• Policy and online charging will become increasingly connected as the
network evolves towards full LTE/IMS.
• The final choice of how to balance revenue and cost will depend on a
particular operator’s situation, but the discussed issues should be
considered with relation to charging, policy control and billing systems;
