A set of Public User Identities that belong to the same alias group as specified in TS 29.228.

Application Level Gateway (ALG) is an application specific functional entity that allows communication between disparate address realm or IP versions, e.g. an IPv6 node to communicate with an IPv4 node and vice versa, when certain applications carry network addresses in the payloads like SIP/SDP. NA(P)T-PT or NA(P)T is application unaware whereas ALGs are application specific translation entities that allow a host running an application to communicate transparently with another host running the same application but in a different IP version or IP address realm. See RFC 2663 for more details. For IMS, an IMS ALG provides the necessary application function for SIP/SDP protocols in order to communicate between different address realms or IP versions, e.g. IPv6 and IPv4 SIP applications.

as defined in TS 24.525.

used in relation to wildcarded Public User/Service Identities to denote an explicitly provisioned Public User/Service Identity. See more details in TS 23.003.

In the case that border control concepts are to be applied in an IM CN subsystem, then these are to be provided by capabilities within the IBCF, and the IBCF acts as an entry point for this network (instead of the I-CSCF). In this case the IBCF and the I-CSCF can be co-located as a single physical node. If border control concepts are not applied, then the I-CSCF is considered as an entry point of a network. If the P-CSCF is in the home network, then the I-CSCF is considered as an entry point for this document.

If operator preference requires the application of border control concepts then these are to be provided by capabilities within the IBCF, and requests sent towards another network are routed via a local network exit point (IBCF), which will then forward the request to the other network (discovering the entry point if necessary).

A Geographical Identifier identifies a geographical area within a country or territory. See more details in clause E.8.

A local service number that is used to access a service in the roamed network (a local service where the subscriber is located).

A local service number is used to access a service that is located in the home network of the user.

This refers to one or more SBI capable HSS instances managing a specific set of IMPIs/IMPUs.

IMS Credentials as defined in TR 21.905.

An IMS application reference is the means by which an IMS communication service identifies an IMS application.

An IMS application is an application that uses an IMS communication service(s) in order to provide a specific service to the end-user. An IMS application utilises the IMS communication service(s) as they are specified without extending the definition of the IMS communication service(s).

An IMS communication service identifier uniquely identifies the IMS communication service associated with the particular IMS request.

An IMS communication service is a type of communication defined by a service definition that specifies the rules and procedures and allowed medias for a specific type of communication and that utilises the IMS enablers.

An IMS enabler is a set of IMS procedures that fulfils specific function. An IMS enabler may be used in conjunction with other IMS enablers in order to provide an IMS communication service.

An identifier, that uniquely identifies a specific UE amongst all other UEs registered with the same Public User Identity.

The interface which is used to interconnect two IM CN subsystem networks. This interface is not constrained to a single protocol.

Unidirectional flow of IP packets with the following properties:

refers to the collection of network entities and interfaces that provides the underlying IP transport connectivity between the UE and the IMS entities. An example of an "IP-Connectivity Access Network" is GPRS.

An IP-SM-GW is an AS providing the support of Short Message Service of the IMS domain. See more details in TS 23.204.

A local service number is a telephone number in non-international format. A local service number is used to access a service that may be located in the home network of the user (home local service number) or the roamed network of the user (geo-local service number).

One or more IP flows carrying a single media instance, e.g., an audio stream or a video stream. In the context of this specification the term Media Flow is used instead of IP Flow regardless of whether the actual IP packet corresponds to media plane information (e.g. audio RTP flow) or control signalling (e.g. RTCP or SIP Signalling).

Based on TS 22.153. Multimedia Priority Service allows authorized users to obtain and maintain radio and network resources with priority, also during national security or emergency situations when PLMN congestion may occur.

A session (e.g., voice, video, data session) for which priority treatment is applied for allocating and maintaining radio and network resources.

A UE having a USIM with MPS subscription.

NAT-PT uses a pool of globally unique IPv4 addresses for assignment to IPv6 nodes on a dynamic basis as sessions are initiated across the IP version boundaries. NAT-PT binds addresses in IPv6 network with addresses in IPv4 network and vice versa to provide transparent routing between the two IP domains without requiring any changes to end points, like the UE. NAT-PT needs to track the sessions it supports and mandates that inbound and outbound data for a specific session traverse the same NAT-PT router. NAPT-PT provides additional translation of transport identifier (e.g., TCP and UDP port numbers, ICMP query identifiers). This allows the transport identifiers of a number of IPv6 hosts to be multiplexed into the transport identifiers of a single assigned IPv4 address. See RFC 2766 for more details.

method by which IP addresses are mapped from one group to another, transparently to end users. Network Address Port Translation, or NA(P)T is a method by which many network addresses and their TCP/UDP (Transmission Control Protocol/User Datagram Protocol) ports are translated into a single network address and its TCP/UDP ports. See RFC 3022 for further details.

Managing Client Initiated Connections in the Session Initiation Protocol (Outbound) defines behaviours for User Agents, registrars and proxy servers that allow requests to be delivered on existing connections established by the User Agent. See RFC 5626 for further details.

An IMS service that allows a specific long distance circuit carrier to be selected for a long distance call.

An IMS service that allows the subscriber to select a long distance circuit carrier per call when dialling a call origination.

According to TS 22.153.

A non-public network not relying on network functions provided by a PLMN.

Simple Traversal of UDP Through NAT (STUN), provides a toolkit of functions. These functions allow entities behind a NAT to learn the address bindings allocated by the NAT, to keep those bindings open, and communicate with other STUN-aware devices to validate connectivity. See RFC 5389 for further details.

Is a usage of STUN, to keep NAT bindings open.

Is a usage of STUN, that allows a client to request an address on the STUN server itself, so that the STUN server acts as a relay. See RFC 5766 for further details.

A Subscriber is an entity (comprising one or more users) that is engaged in a Subscription with a service provider. The subscriber is allowed to subscribe and unsubscribe services, to register a user or a list of user authorized to enjoy these services, and also to set the limits relative to the use that users make of these services.

A unique identifier of transport-layer address, i.e. a combination of a network address, protocol identifier and port number. For example an IP address and a UDP port.

Reference Point between an AS and an MRFC for media control.

Reference Point between a CSCF and an HSS.

Reference Point between an I-CSCF and an SLF.

Reference point between GPRS and an external packet data network.

Reference Point between a UE and a P-CSCF or between an IP-PBX and a P-CSCF.

Reference Point between a CSCF and an Application Server and between a CSCF and an MRB.

Interface between the RNS and the core network. It is also considered as a reference point.

Reference Point between IBCF and TrGW.

Reference Point between an IBCF and another IBCF belonging to a different IM CN subsystem network or between an IBCF and an IP-PBX.

Reference Point between a TrGW and another TrGW belonging to a different IM CN subsystem network.

Reference Point between an AS and a GMLC.

Reference Point between an AS and an I-CSCF.

Reference Point used for IMS media transport to IP network services.

Reference Point between a transit function and AS.

Reference Point between an MGCF and a CSCF.

Reference Point between a CSCF and a BGCF.

Reference Point between a BGCF and an MGCF.

Reference Point between a BGCF/IMS ALG and another BGCF.

Reference Point between a IBCF/CSCF/BGCF/IMS ALG and an IP multimedia network.

Reference Point between an CSCF and an MRFC.

Reference Point between an AS and an MRFC for session control.

Reference Point between MRFP and MRFC.

Reference point between an IBCF and Application Server

Reference Point between a CSCF and another CSCF.

Reference Point between a CSCF/BGCF and IBCF.

Reference Point between an AS and an MRB.

Reference Point between an AS (SIP-AS or OSA-CSCF) and an HSS.

Reference Point between an IM-SSF and an HSS.

Reference Point between UE and an Application Server.

5G System

Application Program Interface

Access Point Name

Application Server

Basic Call State Model

Border Gateway

Breakout Gateway Control Function

Bearer Service

Customised Application Mobile Enhanced Logic

Camel Application Part

Charging Data Record

Core Network

Circuit Switched

Call Session Control Function

CAMEL Service Environment

Dynamic Host Configuration Protocol

Data Network Name

Domain Name System

Explicit Congestion Notification

E.164 Number Mapping

Gateway GPRS Support Node

Group and List Management Server

Gateway Mobile Location Centre

Globally Routable User Agent URI

Generic User Profile

Home Subscriber Server

Interconnection Border Control Function

Interrogating-CSCF

Internet Engineering Task Force

IP Multimedia

IMS Credentials

IP Multimedia Core Network Subsystem

IMS Application Level Gateway

International Mobile Subscriber Identifier

Intelligent Network

Internet Protocol

Internet Protocol version 4

Internet Protocol version 6

IP-Connectivity Access Network

IP Short Message Gateway

Integrated Services Digital Network

IMS SIM

Internet Service Provider

ISDN User Part

Interworking Function

Number portability

Mobile Application Part

Media Gateway Control Function

Media Gateway Function

Media Resource Broker

Multimedia Resource Function Controller

Multimedia Resource Function Processor

Network Access Identifier

Network Address Port Translation

Network Address Translation

Network Address (Port-Multiplexing) Translation-Protocol Translation

Inter-IMS Network to Network Interface

Open Services Architecture

Proxy-CSCF

Policy and Charging Control

Policy and Charging Enforcement Function

Policy and Charging Rules Function

Packet Data Network

Packet Data Protocol e.g., IP

Public Globally Routable User Agent URI

Public Land Mobile Network

Public Service Identity

Public Switched Telephone Network

Quality of Service

Radio Access Bearer

Request for Comments

Service Capability Server

Serving-CSCF

Session Description Protocol

Serving GPRS Support Node

Subscription Locator Function

Stand-alone Non-Public Network

Service Switching Function

Signalling System 7

Subscriber Identity Module

Session Initiation Protocol

Signalling Gateway

Telephony Application Server

Temporary Globally Routable User Agent URI

Topology Hiding Inter-network Gateway

Transition Gateway

User Equipment

Universal Mobile Telecommunications System

Universal Resource Locator

UMTS SIM