3  Definitions, symbols and abbreviations  Word‑p. 21

3.1  Definitions

Refer to TS 23.002 for the definitions of some terms used in this document.

For the purposes of the present document the terms and definitions given in TR 21.905 and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905.

For the purposes of the present document, the following terms and definitions given in TS 23.003 apply:

Distinct Public Service Identity

Public User Identity

Wildcarded Public User Identity

Wildcarded Service User Identity

Alias Public User Identities:

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

ALG:

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.

Distinct Public User Identity:

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.

Entry point:

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.

Exit point:

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).

IP-Connectivity Access Network:

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.

Business trunking:

as defined in TS 24.525.

Subscriber:

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.

Inter-IMS Network to Network Interface:

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

Network Address Translation (NA(P)T):

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.

NAT-PT/NAPT-PT:

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.

Transport address:

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.

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).

IMS application reference:

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

IMS communication service:

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.

IMS communication service identifier:

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

IMC:

IMS Credentials as defined in TR 21.905.

IMS enabler:

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.

Instance identifier:

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

Local Service Number:

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).

Geo-local service number:

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

Geographical Identifier:

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

Home local service number:

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

HSS Group ID:

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

IP Flow:

Unidirectional flow of IP packets with the following properties:

• same source IP address and port number;
• same destination IP address and port number;
• same transport protocol (port numbers are only applicable if used by the transport protocol).

IP-SM-GW (IP short message gateway):

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.

Media Flow:

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).

MPS:

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.

MPS session:

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

MPS-subscribed UE:

A UE having a USIM with MPS subscription.

Outbound:

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.

Preferred Circuit Carrier Selection:

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

Preferred Circuit Carrier Access:

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

Service User:

According to TS 22.153.

STUN:

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.

STUN Relay:

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 IETF RFC 5766 for further details.

STUN Keep-alive:

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

3.2  Symbols  Word‑p. 23

For the purposes of the present document the following symbols apply:

Cr

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

Cx

Reference Point between a CSCF and an HSS.

Dx

Reference Point between an I-CSCF and an SLF.

Gi

Reference point between GPRS and an external packet data network.

Gm

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

ISC

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

Iu

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

Ix

Reference Point between IBCF and TrGW.

Ici

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

Izi

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

Le

Reference Point between an AS and a GMLC.

Ma

Reference Point between an AS and an I-CSCF.

Mb

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

Mf

Reference Point between a transit function and AS.

Mg

Reference Point between an MGCF and a CSCF.

Mi

Reference Point between a CSCF and a BGCF.

Mj

Reference Point between a BGCF and an MGCF.

Mk

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

Mm

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

Mr

Reference Point between an CSCF and an MRFC.

Mr'

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

Mp

Reference Point between MRFP and MRFC.

Ms

Reference point between an IBCF and Application Server

Mw

Reference Point between a CSCF and another CSCF.

Mx

Reference Point between a CSCF/BGCF and IBCF.

Rc

Reference Point between an AS and an MRB.

Sh

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

Si

Reference Point between an IM-SSF and an HSS.

Ut

Reference Point between UE and an Application Server.

3.3  Abbreviations  Word‑p. 24

For the purposes of the present document, the abbreviations given in TR 21.905 and the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in TR 21.905.

5GS

5G System

API

Application Program Interface

APN

Access Point Name

AS

Application Server

BCSM

Basic Call State Model

BG

Border Gateway

BGCF

Breakout Gateway Control Function

BS

Bearer Service

CAMEL

Customised Application Mobile Enhanced Logic

CAP

Camel Application Part

CDR

Charging Data Record

CN

Core Network

CS

Circuit Switched

CSCF

Call Session Control Function

CSE

CAMEL Service Environment

DHCP

Dynamic Host Configuration Protocol

DNN

Data Network Name

DNS

Domain Name System

ECN

Explicit Congestion Notification

ENUM

E.164 Number Mapping

GGSN

Gateway GPRS Support Node

GLMS

Group and List Management Server

GMLC

Gateway Mobile Location Centre

GRUU

Globally Routable User Agent URI

GUP

Generic User Profile

HSS

Home Subscriber Server

IBCF

Interconnection Border Control Function

I-CSCF

Interrogating-CSCF

IETF

Internet Engineering Task Force

IM

IP Multimedia

IMC

IMS Credentials

IMS

IP Multimedia Core Network Subsystem

IMS ALG

IMS Application Level Gateway

IMSI

International Mobile Subscriber Identifier

IN

Intelligent Network

IP

Internet Protocol

IPv4

Internet Protocol version 4

IPv6

Internet Protocol version 6

IP-CAN

IP-Connectivity Access Network

IP-SM-GW

IP Short Message Gateway

ISDN

Integrated Services Digital Network

ISIM

IMS SIM

ISP

Internet Service Provider

ISUP

ISDN User Part

IWF

Interworking Function

NP

Number portability

MAP

Mobile Application Part

MGCF

Media Gateway Control Function

MGF

Media Gateway Function

MRB

Media Resource Broker

MRFC

Multimedia Resource Function Controller

MRFP

Multimedia Resource Function Processor

NAI

Network Access Identifier

NAPT

Network Address Port Translation

NAT

Network Address Translation

NA(P)T-PT

Network Address (Port-Multiplexing) Translation-Protocol Translation

II-NNI

Inter-IMS Network to Network Interface

OSA

Open Services Architecture

P-CSCF

Proxy-CSCF

PCC

Policy and Charging Control

PCEF

Policy and Charging Enforcement Function

PCRF

Policy and Charging Rules Function

PDN

Packet Data Network

PDP

Packet Data Protocol e.g., IP

P-GRUU

Public Globally Routable User Agent URI

PLMN

Public Land Mobile Network

PSI

Public Service Identity

PSTN

Public Switched Telephone Network

QoS

Quality of Service

RAB

Radio Access Bearer

RFC

Request for Comments

SCS

Service Capability Server

S-CSCF

Serving-CSCF

SDP

Session Description Protocol

SGSN

Serving GPRS Support Node

SLF

Subscription Locator Function

SSF

Service Switching Function

SS7

Signalling System 7

SIM

Subscriber Identity Module

SIP

Session Initiation Protocol

S-GW

Signalling Gateway

TAS

Telephony Application Server

T-GRUU

Temporary Globally Routable User Agent URI

THIG

Topology Hiding Inter-network Gateway

TrGW

Transition Gateway

UE

User Equipment

UMTS

Universal Mobile Telecommunications System

URL

Universal Resource Locator

USIM

UMTS SIM

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