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3GPP Glossaries



Network entities











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SCC AS     # SCEF     # S-CSCF     # SEG     # SGSN     # S4-SGSN     # SGW     # S-GW     # SIM     # SIWFC     # SIWFS     # SLF     # SMLC     # SMS-GMSC     # SMS-IWMSC     # SMS-SC     # SPR    


SCC AS  —  Service  Centralization and  Continuity    Application  Server

[IMS  R8]+

The SCC AS is an IMS Application that can provide functionality required to enable IMS Centralized Services as defined in TS 23.292, and can provide IMS-based mechanisms for enabling service continuity of multimedia sessions as defined in TS 23.237.

Source:   TS 23.002, clause 4a.7.11

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SCEF  —  Service  Capability  Exposure  Function

[PCC  R13]+

The Service Capability Exposure Function (SCEF) provides a means to securely expose the services and capabilities provided by 3GPP network interfaces. The SCEF provides a means for the discovery of the exposed service capabilities. The SCEF provides access to network capabilities through homogenous network application programming interfaces (e.g. Network API) defined by OMA, GSMA, and possibly other standardisation bodies. The SCEF abstracts the services from the underlying 3GPP network interfaces and protocols.

Source:   TS 23.682, clause 4.4.8

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S-CSCF  —  Server    Call  Session  Control  Function

[IMS  R5]+

The Serving-CSCF (S-CSCF) performs the session control services for the UE. It maintains a session state as needed by the network operator for support of the services. Within an operator's network, different S-CSCFs may have different functionalities. The main functions performed by the S-CSCF during a session are:

For Registration:
  • May behave as a Registrar as defined in IETF SIP RFCs, i.e. it accepts registration requests and makes its information available through the location server (e.g. HSS).
  • The S-CSCF shall notify subscribers about registration changes.
  • During registration process, the S-CSCF shall provide policy information, if available, for a Public User Identity from the HSS to the P-CSCF and/or UE.
For Session-related and session-unrelated flows:
  • Session control for the registered endpoint's sessions.
  • May behave as a Proxy Server as defined in IETF SIP RFCs, i.e. it accepts requests and services them internally or forwards them on, possibly after translation.
  • May behave as a User Agent as defined in IETF SIP RFCs, i.e. it may terminate and independently generate SIP transactions.
  • Based on the determined served user, handle interaction with Services Platforms for the support of Services
  • Provide endpoints with service event related information (e.g. notification of tones/announcement together with location of additional media resources, billing notification)

Source:   TS 23.228, clause 4.6.3

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SEG  —  SEcurity  Gateway

[NDS  R4]+

The interface between different security domains is protected by SEGs. The SEGs are responsible for enforcing the security policy of a IP security domain towards other SEGs in the destination IP security domain. All NDS/IP traffic shall pass through a SEG before entering or leaving a security domain. For further details of SEG, see TS 33.210.

Source:   TS 23.002, clause 4a.10

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SGSN  —  Serving  GPRS  Support  Node

[PS Domain  R97]+

The location register function in the SGSN stores two types of subscriber data needed to handle originating and terminating packet data transfer:
  • subscription information: the IMSI; one or more temporary identities; zero or more PDP addresses.
  • location information:
    • depending on the operating mode of the MS, the cell or the routeing area where the MS is registered;
    • the VLR number of the associated VLR (if the Gs interface is implemented);
    • the GGSN address of each GGSN for which an active PDP context exists.
The SGSN provides support for Direct Tunnel functions as specified in TS 23.060.

The organisation of the subscriber data in the SGSN is defined in TS 23.008 and TS 23.060.

The procedures for information transfer between the SGSN, the GGSN, the VLR and the HLR are defined in TS 23.016 and TS 23.060.

Source:   TS 23.002, clause

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S4-SGSN  —  S4    Serving  GPRS  Support  Node

[EPS  R8]+

Evolved SGSN that enables the connection of GERAN/UTRAN to the EPC.

Source:   –

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SGW  —  Signalling  GateWay

[CS Domain  R4]+

The SGW performs the signalling conversion (both ways) at transport level between the SS7 based transport of signalling used in pre-Rel-4 networks, and the IP based transport of signalling possibly used in post-R3 networks (i.e. between Sigtran SCTP/IP and SS7 MTP). The SGW does not interpret the application layer (e.g. MAP, CAP, BICC, ISUP) messages but may have to interpret the underlying SCCP or SCTP layer to ensure proper routing of the signalling.

Source:   TS 23.002, clause 4a.8

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S-GW  —  Serving    GateWay

[EPC  R8]+

The Serving GW is the gateway which terminates the interface towards E-UTRAN.

For each UE associated with the EPS, at a given point of time, there is a single Serving GW. For detailed S-GW functions, see TS 23.401 and TS 23.402.

Connectivity to a GGSN is not supported.

The functions of the Serving GW include:
  • the local Mobility Anchor point for inter-eNodeB handover;
  • Mobility anchoring for inter-3GPP mobility;
  • ECM-IDLE mode downlink packet buffering and initiation of network triggered service request procedure;
  • Lawful Interception;
  • Packet routeing and forwarding;
  • Transport level packet marking in the uplink and the downlink;
  • Accounting on user and QCI granularity for inter-operator charging;
  • A local non-3GPP anchor for the case of roaming when the non-3GPP IP accesses connected to the VPLMN;
  • Event reporting (change of RAT, etc.) to the PCRF;
  • Uplink and downlink bearer binding towards 3GPP accesses as defined in TS 23.203;
  • Uplink bearer binding verification with packet dropping of "misbehaving UL traffic";
  • Mobile Access Gateway (MAG) functions if PMIP-based S5 or S8 is used;
  • Support necessary functions in order for enabling GTP/PMIP chaining functions.

Source:   TS 23.002, clause

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SIM  —  Subscriber  Identity  Module

[MS  R96]+

A GSM MS comprises an ME and a SIM. The SIM is a removable module. The SIM contains the International Mobile Subscriber Identity (IMSI) which unambiguously identifies a subscriber. Without a valid IMSI, GSM service is not accessible (except emergency calls, as defined in TS 02.03). The user interface (MMI) of the ME related to SIM operations is defined in TS 02.30. TS 02.09 specifies a security function for authenticating the SIM. This function, which is mandatory for any MS, is based on a cryptographic algorithm, A3, and a secret subscriber authentication key, Ki, both of which are located in the SIM. The SIM provides storage of subscriber related information. This data is of three types:
  • data fixed during administrative phase; e.g. IMSI, subscriber authentication key, access control class;
  • temporary network data; e.g. TMSI, LAI, Kc, Forbidden PLMNs;
  • service related data; e.g. Language Preference, Advice of Charge.
The SIM contains Card Holder Verification information (CHV1 - see clause 5) to provide protection against unauthorized use. For some optional features, the use of a second CHV (CHV2) is required. CHV(s) shall be stored and verified within the SIM.

The SIM may also contain applications which use the features defined in the SIM Application Toolkit specification TS 11.14.

Source:   TS 42.017, Rel-4

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SIWFC  —  Shared  Inter  Working  Function  Controller

[CS Domain  R96-98]

The visited MSC is responsible for allocation of an IWF or a SIWFS. In the case the visited MSC has the additional functions required to provide a SIWF, this additional functionality in the visited MSC is called SIWFC. SIWFC is a logical part of the MSC.

Source:   TS 03.54

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SIWFS  —  Shared  Inter  Working  Function  Server

[CS Domain  R96-98]

The logical entity that contains the IWU is called SIWF Server (SIWFS). It offers IWU to remotely located MSCs. The IWU provides the traffic channel related functions. SIWFS contains also the DRM which is needed for the additional signalling between entities involved i.e. the visited MSC and the SIWFS.

Source:   TS 03.54

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SLF  —  Subscription  Locator  Function

[IMS  R5]+

The SLF:
  • Is queried by the I-CSCF during the Registration and Session Setup to get the name of the HSS containing the required subscriber specific data. Furthermore the SLF is also queried by the S-CSCF during the Registration.
  • Is queried by the AS in conjunction with the Sh interface operation to get the name of the HSS containing the required subscriber specific data
  • Is queried by the 3GPP AAA server to get the name of the HSS containing the required subscriber specific data
  • Is accessed via the Dx interface by the CSCF, via the Dh interface by the AS, and via the Dw interface by the 3GPP AAA Server.
The SLF is not required in a single HSS environment. An example for a single HSS environment is a server farm architecture. Use of SLF is not required when AS are configured/managed to use pre-defined HSS.

Source:   TS 23.002, clause

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SMLC  —  Serving  Mobile  Location  Center

[LCS  R98]+

The SMLC node is responsible for managing the overall co-ordination and scheduling of resources required to perform positioning of a mobile, and calculating the final location estimate and accuracy. There may be more than one SMLC in a PLMN.

Source:   TS 03.02, clause 2.19

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SMS-GMSC  —  Short  Message  Service    Gateway  Mobile-services  Switching  Centre

[SMS  R96]+

The SMS Gateway MSC (SMS-GMSC) acts as an interface between a Short Message Service Centre and the PLMN, to allow short messages to be delivered to mobile stations from the Service Centre (SC).

The choice of which MSCs can act as SMS Gateway MSCs is a network operator matter (e.g. all MSCs or some designated MSCs).

Source:   TS 23.002, clause

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SMS-IWMSC  —  Short  Message  Service    InterWorking  Mobile-services  Switching  Centre

[SMS  R96]+

The SMS Interworking MSC acts as an interface between the PLMN and a Short Message Service Centre (SC) to allow short messages to be submitted from Mobile Stations to the SC.

The choice of which MSCs can act as SMS Interworking MSCs is a network operator matter (e.g. all MSCs or some designated MSCs).

Source:   TS 23.002, clause

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SMS-SC  —  Short  Message  Service    Service  Centre

[SMS  R96]+

Function responsible for the relaying and store-and-forwarding of a short message between an SME (Short Message Entity) and an MS.

Source:   TS 23.040, clause 6

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SPR  —  Subscription  Profile  Repository

[PCC  R8]+

The SPR logical entity contains all subscriber/subscription related information needed for subscription-based policies and charging control by the PCRF.

Source:   TS 23.002, clause 4a.20

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