3 Definitions, symbols and abbreviations
23.2283GPPIP Multimedia Subsystem (IMS)Release 18Stage 2TS
3.1 Definitions
Refer to TS 23.002 [1] 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 [68] 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 [68].
For the purposes of the present document, the following terms and definitions given in TS 23.003 [24] 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 [30].
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 IETF RFC 2663 [34] 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.
Business trunking: as defined in TS 24.525 [81].
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 [24].
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).
Geographical Identifier: A Geographical Identifier identifies a geographical area within a country or territory. See more details in clause E.8.
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).
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.
IMC: IMS Credentials as defined in TR 21.905 [68].
IMS application reference: An IMS application reference is the means by which an IMS communication service identifies an IMS application.
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 communication service identifier: An IMS communication service identifier uniquely identifies the IMS communication service associated with the particular IMS request.
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 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.
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.
IP Flow: Unidirectional flow of IP packets with the following properties:
– same destination IP address and port number;
– same source IP address and port number;
– same transport protocol (port numbers are only applicable if used by the transport protocol).
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.
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 [56].
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).
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 [77]. 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.
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 IETF RFC 2766 [33] for more details.
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 [65] for further details.
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 [48] for further details.
Preferred Circuit Carrier Access: An IMS service that allows a specific long distance circuit carrier to be selected for a long distance call.
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.
Service User: According to TS 22.153 [77].
Stand-alone Non-Public Network: A non-public network not relying on network functions provided by a PLMN.
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 [47] for further details.
STUN Keep-alive: Is a usage of STUN, to keep NAT bindings open.
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 [46] for further details.
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.
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.
3.2 Symbols
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
For the purposes of the present document, the abbreviations given in TR 21.905 [68] 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 [68].
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
SNPN Stand-alone Non-Public Network
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