DIAMETER Applications in Telecommunications

1 Copyright EFORT 20131 DIAMETERA pplicationsin first tutorial proposed by EFORT has presented the DIAMETER base protocol. A secondtutorial has described the DIAMETER signaling network with the concept of agent as theDIAMETER router in this network. This tutorial lists the DIAMETER Applications related totelecommunications, particularly those used in EPS (Evolved Packet System), IMS (IPMultimedia Subsystem), PCC (Policy and Charging Control) and GAA/GBA (GenericAuthentication Architecture / Generic Bootstrapping Architecture).The 4G network also called EPS (Evolved Packet System) is an all IP ofan access network calledLTE (Long Term Evolution) and a new packet switched corenetwork calledePC (Evolved Packet Core).

2 All AAA (Authentication, Authorization andAccounting) procedures in EPS are DIAMETER 4G, IP-based services proposed by the service provider including telephony services willrely on IMS (IP Multimedia Subsystem). IMS is also an all IP architecture with DIAMETER asthe AAA service providers need to control the usage of mobile data tolimit the bandwidthavailable to its heaviest users (fair use), to accept/block/downgrade IP service flows ( ,downgrade theskype flow). Furthermore, the service provider should enhance theQoS forits proposed IP-based services that need thatQoS ( , Voice over IP, Mobile TV), etc.

3 Thearchitecture which enables the control of IP service flows (accept, block, downgrade theQoS, enhance theQoS) and enables the charging of these IP service flows is PCC (Policyand Charging Control).All the interfaces of the PCC architecture are DIAMETER -basedsince PCC is about authorization and enables service-based mobile authentication, independently of access-based ornetwork-based mobile service authentication procedure uses are other Telecommunications architectures which use DIAMETER and which are notpresented in this tutorial, such as M2M; M2M uses DIAMETER Applications calledTsp, S6m,T4, than 80 DIAMETER Applications have already been defined for Telecommunications ,particularly by Applications3 GPP defines a number of Applications based on DIAMETER protocol.

4 These applicationsare also named related to the EPS architecture are (Figures 1, 2 and 3) : S6a (EPS) : S6a interface enables transfer of subscription and authentication data forauthenticating / authorizing user access to the evolved packet system (EPS). Thisinterface is between MME (Mobility Management Entity) and HSS (Home SubscriberServer). S6d (EPS) : S6d enables the transfer of subscriber related data between the S4-SGSNand the HSS. S13 (EPS) : S13 is an interface between the MME and the EIR (Equipment IdentityRegister) in EPS. It allows validating the IMEI EFORT 20132 S13 (EPS) : S13 is aninterface between the S4-SGSN and the EIR, which provides anidentical service to S13.

5 SWx (EPS): TheSWx interfaceisdefinedbetween the HSSand the 3 GPP AAAserverfor non-3 GPPaccess ( ,WiFi) to EPSandissimilar to S6. SWm (EPS): TheSWm interfaceisdefinedbetween theePDG(EvolvedPacket DataGateway)and the 3 GPP AAAserver orbetween theePDGand the 3 GPP AAAproxy fornon-trusted non-3 GPPaccess to EPS. Sta (EPS): TheSTa interfaceisdefinedbetween thetrusted non-3 GPP IPaccesscalledTWAN (TrustedWireless Access Network) to EPSand the 3 GPP AAAserver in thenon-roaming case. In theroaming caseitisdefinedbetween the TWANand the 3 GPP AAAproxy. SWa (EPS): TheSWa interfaceisdefinedbetween thenon-trusted non-3 GPP IPaccessand the 3 GPP AAAserver (non-roaming case) or 3 GPP AAAproxy (roaming case).

6 TheSWa interfaceisused for 3 GPP-basedaccessauthenticationandauthoriz ationwith annon-trusted supportsreporting ofaccounting informationgenerated by theaccess network. SWd (EPS): TheSWd interfaceisdefinedbetween the 3 GPP AAAproxyand the 3 GPPAAA server. TheSWd interfaceisused inroamingscenarioswhere the 3 GPP AAAproxyislocated in thevisited networkand the 3 GPP AAAserverislocated in the homenetwork. The 3 GPP AAAproxyacts as aDiameterproxy agentandforwardsDiametercommandsbetween theDiameter clientand theDiameterserver. S6b (EPS): The S6b interfaceisdefinedbetween the PDN GWand the 3 GPP AAAserver (fornon-roaming case, orroamingwith homeroutedtraffic to PDN GW in homenetwork)andbetween the PDN GWand the 3 GPP AAAproxy (forroaming casewithPDN GW in thevisited network, localbreakout).

7 SLg (EPS) :SLgis an interfacewhichenables the GMLC obtaining UE locationinformationfrom MME. Lgd (EPS) :SLgis an interfacewhichenables the GMLC obtaining UE locationinformationfrom SGSN. SLh (EPS) :SLhis an interfacewhichenables the GMLC obtaining UE locationinformationfrom 1 : DIAMETER Interfaces in EPS ArchitectureHSSEIRHSS : Home Subscriber ServerEIR : Equipment Identity RegisterMME : Mobility Management EntitySGSN : Serving GPRS Support nodeGMLC : Gateway Mobile Location ServerS6aS13 MMES4-SGSNS6dS13 3 GPPAAAS erverSWxGMLCSLhSLgLgdCopyright EFORT 20133 Figure 2 : DIAMETER Interfaces fornon-trusted non-3 GPPaccess to EPSF igure 3 : DIAMETER Interfaces fortrusted non-3 GPPaccess to EPST hose related to PCC architecture are (Figure 4) : Gx (GPRS/EPS).

8 TheGx interface is located between the Policy and Charging RulesFunction (PCRF) and the Policy and Charging Enforcement Function (PCEF).PCEF maybe embedded in a GGSN or PDN GW. TheGx interface is used for provisioning andremoval of PCC(Policy and Charging Control)rules from the PCRF to the PCEF and thetransmission of traffic plane events from the PCEF to the PCRF. TheGxinterface canalsobe used forapplication s traffic detection and AAAS erverAcc snon-3 GPPF iableSWxWiFiAPUEPDNG atewaySTaTWAN :Trusted WirelessAccess NetworkTWANS6bInterface DIAMETERHSST rustednon-3 GPPA ccessDIAMETER InterfaceSWm3 GPP AAAS erverAcc sNon-3 GPPNonFiableSWxWiFiAPInterface DIAMETERI nterface DIAMETER optionnelleUESWuePDGePDG : Evolved Packet Data GatewayAP : Access PointSWaHSSNon-Trustednon-3 GPPA ccessDIAMETER InterfaceOptionalDIAMETER InterfaceCopyright EFORT 20134 Gxx (EPS) :Gxx is used when the protocol for bearer control is PMIP instead of GTPv2-C.

9 In this case, the access element( ,ePDG,TWAN,Serving GW, etc)embeds aBearer Binding and Event Reporting Function (BBERF).TheGxxinterface is locatedbetween thePCRF and the interface is used for provisioning, updateand removal ofQoS rules from the PCRF to the BBERF and transmission of traffic planeevents from the BBERF to the PCRF. Sd (EPS) :TheSd interface is between the PCRF and the TDF(Traffic DetectionFunction)and is used forapplication s traffic detection and control. Gy (GPRS/EPS) :TheGy interface resides between the OCS and the PCEF ( ,GGSN, PDN GW) andallows online credit control for service data flow based PCEF obtains credits from OCS via this interface.

10 Gz (GPRS/EPS) :TheGz interface resides between the PCEF and the OFCS andenables transport of service data flow based offline charging information. PCEF submitsCDRs viaGz to OFCS. S9 (EPS) :In the roaming case, a PCRF in the home network controls the policies to beapplied. This is done via a PCRF in the visited network over the S9 interface which henceis a roaming interface betweenPCRFs. Rx (EPS) :Rxinterface is between thePCRF and the AF ( , P-CSCF in case of IMS),for transport of application level session information from the AF to the PCRF anddelivery of IP bearer events in the opposite direction. Rf (IMS) :Rf is the interface between IMS entities and CDF (Charge DataFuction) foroffline charging.