home subscriber server (hss)

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Home Subscriber Server(HSS)

By : M.Samie

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Home Subscriber Server

• What is HSS?• HSS in IMS• Main Data in HSS• HSS Subsets • HSS Logical Functions• Reference Points & Interfaces• Subscription Locator Function• Implementation Issues• Maintenance Issues

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What is HSS?

• Is the master database for a given user

• Containing the subscription-related information to support the network entities

• Is considered as Data Repository for IM CN Subsystem user related data

Note : A Home Network may contain one or several HSSs

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HSS in IMS

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IMS Functional Entities

VisitedVisitedNetworkNetworkVisitedVisited

NetworkNetwork

HSSHSSHSSHSSDNSDNSENUMENUMDNSDNS

ENUMENUM

I-CSCFI-CSCFI-CSCFI-CSCF S-S-CSCFCSCF

S-S-CSCFCSCF

Home Network

ASASASASASASASASASASASAS

Home Subscriber Server• Centralized DB• HLR successor• User profile• Filter criteria (sent to S-CSCF)

• Which applications• Which conditions

Home Subscriber Server• Centralized DB• HLR successor• User profile• Filter criteria (sent to S-CSCF)

• Which applications• Which conditions

Application Servers• Push-to-talk• Instant messaging• Telephony AS• 3rd party or IMS Vendor

Application Servers• Push-to-talk• Instant messaging• Telephony AS• 3rd party or IMS Vendor

P-P-CSCFCSCF

P-P-CSCFCSCF

MGCFMGCFMGCFMGCF

MGWMGWMGWMGWPSTNPSTNPSTNPSTN

H.248

ISUPBGCFBGCFBGCFBGCF

SIP

SS7SS7SS7SS7

SIP

SIP

SIP

SIP

SIPSIP

SIP

Diameter

RTP TDM

MSMSMSMS MSMSMSMS

MRFCMRFCMRFCMRFC

Media GatewayControl Function• Interfaces to PSTN/PLMN by

• Converting SIP <-> ISUP• Interworking RTP to circuit

• H.248 control of MGW

Media GatewayControl Function• Interfaces to PSTN/PLMN by

• Converting SIP <-> ISUP• Interworking RTP to circuit

• H.248 control of MGW

Breakout Gateway Control Function• Selects network (MGCF or other BGCF) in which PSTN/ PLMN breakout is to occur

Breakout Gateway Control Function• Selects network (MGCF or other BGCF) in which PSTN/ PLMN breakout is to occur

Media Resource Function Controller• Pooling of Media servers (e.g. conference) Media Resource Function Controller• Pooling of Media servers (e.g. conference)

Proxy CSCF• 1st contact point for UA• QoS• Routes to S-CSCF

Proxy CSCF• 1st contact point for UA• QoS• Routes to S-CSCF

Interrogating CSCF• Entry point for incoming calls• Determines S-CSCF for Subscribers• Hides network topology

Interrogating CSCF• Entry point for incoming calls• Determines S-CSCF for Subscribers• Hides network topology

Serving CSCF• Registrar• Session control• Application Interface

Serving CSCF• Registrar• Session control• Application Interface

P-P-CSCFCSCF

P-P-CSCFCSCF

SIP

SIP

UA/UE

UA/UE

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Main Data in HSS

• Presence, Location and Profile• End-User Identity• Private and Public End-User

Information• Registration Information• Service Initiation Information• Subscriber Service Profile (SSP)

• Downloaded to CSCF at Registration

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HSS Subsets

• Home Location Register (CS Domain)

• Home Location Register (PS Domain)

• Authentication Center (CS Domain)

• Authentication Center (PS Domain)

• IMS related subset

CS Domain

PS Domain

IM C

N

HLR

HLR

AUC

AUC

DR

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Home Location Register

• It is needed to enable subscriber access to the PS Domain services.

• It supports PS Domain entities such as the SGSN and GGSN, through the Gr and Gc interfaces and the 3GPP AAA Server for the I-WLAN through the D'/Gr' interface.

• It is needed to enable subscriber access to the CS Domain services and to support roaming to legacy GSM/UMTS CS Domain networks.

• It supports CS Domain entities such as the MSC and GMSC, through the C and D interfaces.

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Authentication Center

• The AuC is associated with an HLR and stores an identity key for each mobile subscriber registered with the associated HLR.

• The AuC communicates only with its associated HLR over a non-standardised interface denoted the H-interface.

• The HLR requests the data needed for authentication and ciphering from the AuC via the H-interface.

• HLR delivers them to the VLR and SGSN which need them to perform the security functions for a mobile station.

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HSS

Mobility Management

CSCFIM-SSFOSA-SCS

GGSNSGSNGMSC MSC/VLR

PS DomainCS Domain IM CN Subsystem

Applications

GUP Server

AAA Server

SIP Application Server

Identification Handling

User Security Info Generation

Service Authorization

User Security Support Access Authorization

Service Provisioning Support

Application Services Support

Call/Session Establishment Support

CAMEL Services Support

GUP Data Repository SNMP Agent function Support

CxSiShShRp

Rp

Wx, Gr’, Gc’

GcGrDC

3GPP TS 23.002

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HSS Logical Functions

• Mobility Management HSS supports MM by location updating

• Call Session Establishment Support HSS provides information on which

call/session control entity currently hosts the user

• User Security Support The HSS generates user authentication and

ciphering data for the CS and PS Domains and for the IM CN subsystem.

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HSS Logical Functions(Cont.)

• User Identification HandlingThe HSS provides the appropriate relations among

all the identifiers uniquely determining the user in the system

CS Domain (IMSI and MSISDNs) PS Domain (IMSI, MSISDNs and IP addresses) IM CN subsystem (private identities and public

identities)

• Access AuthorizationThe HSS authorises the user for mobile access

when requested by the MSC/VLR, SGSN, 3GPP AAA Server or CSCF, by checking that the user is allowed to roam to that visited network.

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• Service Authorization SupportThe HSS provides basic authorisation for MT call/session

establishment and service invocation.

The HSS updates the appropriate serving entities (i.e., MSC/VLR, SGSN, 3GPP AAA Server, CSCF) with the relevant information related to the services to be provided to the user.

• Service Provisioning Support The HSS provides access to the service profile data for

use within the CS Domain, PS Domain and IM CN subsystem.

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• Application Service and CAMEL Service Support

The HSS communicates with the SIP Application Server and the OSA-SCS to support Application Services in the IM CN subsystem.

The HSS communicates with the IM-SSF to support the CAMEL Services related to the IM CN subsystem.

The HSS communicates with the gsmSCF to support CAMEL Services in the CS Domain and PS Domain.

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• GUP Data Repository The HSS supports the storage of IM CN

Subsystem user related data, and provides access to these data through the Rp reference point by GUP Server*.

* GUP Server is a functional entity providing a single point of access to the Generic User Profile data of a particular subscriber. (TS 23.240)

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HSS and Basic Interfaces

MSC

GMSC SGSN

GGSN

CSCF GUP Server

HSSD

CGr

Gc

Cx Rp

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Reference Points & Interfaces

• Interfaces internal to the CS domain• Interfaces internal to the PS domain• Interfaces used by CS and PS

domains • IM Subsystem Reference Points• Diameter Protocol

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Interfaces to CS domain

HLR - VLR (D-interface)(TS 29.002)

Is used to exchange the data related to the location of the mobile station and the management of the subscriber.

Signalling on this interface uses the Mobile Application Part (MAP), which in turn uses the services of Transaction Capabilities.

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Interfaces to CS domain

HLR - MSC (C-interface) (TS 29.002)

The Gateway MSC must interrogate the HLR of the required subscriber to obtain routing information for a call or a short message directed to that subscriber.


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Interfaces to PS domain

HLR – SGSN (Gr-interface)(TS 29.002)

This interface is used to exchange the data related to the location of the mobile station and to the management of the subscriber.


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Interfaces to PS domain

HLR – GGSN (Gc-interface)(TS 29.002)

Is used by the GGSN to retrieve information about the location and supported services for the mobile subscriber, to be able to activate a packet data network address.


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Interfaces used by CS and PS domains

HLR - AuC (H-interface)When an HLR receives a request for

authentication and ciphering data for a Mobile Subscriber and it does not hold the requested data, the HLR requests the data from the AuC.

The protocol used to transfer the data over this interface is not standardised.

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IM Subsystem Reference Points

• HSS – CSCF (Cx Reference Point)• HSS – SIP AS or OSA SCS (Sh Reference Point)• HSS – CAMEL IM-SSF (Si Reference Point) • AAA Server - HLR (D'/Gr' Reference Point)• AAA Server - HSS (Wx Reference Point)• GUP Server – HSS (Rp Reference Point)• Applications – HSS (Rp Reference Point)• CSCF- SLF (Dx Reference Point) • AS- SLF (Dh Reference Point)• AAA Server - SLF (Dw reference point)

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HSS – CSCF (Cx Reference Point) (TS 23.228)

Procedures related to Serving CSCF assignment

Procedures related to routing information: retrieval from HSS to CSCF

Procedures related to authorisation (e.g., checking of roaming agreement)

Procedures related to authentication: transfer of security parameters of the subscriber between HSS and CSCF

Procedures related to filter control: transfer of filter parameters of the subscriber from HSS to CSCF

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AAA Server - HSS (Wx Reference Point)AAA Server - HLR (D'/Gr' Reference Point)

(TS 23.234)

Retrieval of authentication vectors

Retrieval of WLAN access-related subscriber information (profile)

Registration of the 3GPP AAA Server of an authorised WLAN user in the HSS

Indication of change of subscriber profile

Retrieval of online/offline charging

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GUP Server – HSS Applications – HSS (Rp Reference Point)

(TS 23.240)

Enables the GUP Server and the Applications to access GUP Data Repositories

The HSS is one of the GUP Data Repositories. It stores the IM CN Subsystem user related data.

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Diameter Protocol

• Is a signaling protocol that has been specified by IETF (RFC 3588 – 3589)

• IS defined as a base protocol used in conjunction with a set of applications

• It provides mechanisms for reliable transport, message delivery and error handling between Diameter clients and servers.

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Diameter Functions

• Delivery of AVPs (Attribute Value Pair)• Capabilities negotiation• Error notification• Basic Services necessary for applications,

such as handling of user sessions or accounting

Note : Diameter can be extended through addition of new commands and AVPs for set of new application requirements

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Subscription Locator Function

(SLF)

Is used as a resolution mechanism that enables the I-CSCF, the S-CSCF and the AS to find the address of the HSS that holds the subscriber data for a given user identity when multiple and separately addressable HSSs have been deployed by the network operator.

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CSCF- SLF (Dx Reference Point) AS- SLF (Dh Reference Point)

AAA Server - SLF (Dw reference point)(TS 23.228)

Is used to retrieve the address of the HSS which holds the subscription for a given user.

Is not required in a single HSS environment.

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Implementation Issues

• In IMS arch. the HSS is a central database that contains all of the information needed to properly control sessions.

• Functions in the network interact with the HSS using IETF Diameter Protocol.

• The HSS is involved in every session and maybe queried multiple times during a call so it must have high performance.

• The HSS must be exceptionally reliable, as without it sessions cannot be created.

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Implementation Issues• Software Modules

Agents supports protocols and Interfaces Information Storage & Retrieval Module Agents supports authorization requested by

components Other functions inherited from PS & CS domains

• Data Organization Storage Media

■ Memory Hierarchy■ Efficient/Reliable Transfer

– Hardware Techniques ( RAID disks )– Software Techniques ( Buffer Mgmt )

Storage Strategies■ Tuples on Disks■ Tuples on Pages, Clusters, …

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Maintenance Issues

• The main issue is adding capacity while maintaining performance

Simply adding processing power on HSS Adding additional mirror database nodes either at

the same location or distributed geographically Segregating different groups of subscribers in

different databases

Result is a network that seamlessly support growth to millions call per “Busy Hour” without stressing any single point in the network

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Any Question?

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Data in HSSThe main data stored in the HSS include [3GPP

TS 23.002]: User identities

private user identities public user identities

registration information access parameters

user authenticationallocated S-CSCF names roaming authorization

service-triggering information

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Subscriber Data

• Subscriber data for CS and PS domains• Subscriber data for IP Multimedia

domain

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Subscriber data for CS and PS domains

(TS 23.008)• Data related to subscription, identification and numbering • Data related to Mobile Station types• Data related to authentication and ciphering • Data related to roaming • Data related to basic services• Data related to supplementary services • Mobile station status data • Data related to Operator Determined Barring • Data related to handover• Data related to short message support • Data related to subscriber trace • Data related to the support of voice group and broadcast calls• Data related to GPRS NAM • Data related to CAMEL• Data related to charging

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Subscriber data for IP Multimedia domain

(TS 23.008) • Data related to subscription, identification and

numbering • Data related to registration • Data related to authentication and ciphering • Data related S-CSCF selection information • Data related to Application and service triggers • Data related to Core Network Services

Authorization• Data related to Charging • Data related to CAMEL Support of IMS Services

home subscriber server (hss)

Documents

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imsmain data

mobile subscriber

subscriber access

home subscriber serverhssby

data repository

cs domain services

cs domain entities