For the purposes of the present document, the following terms and definitions apply:
IM CN subsystem:
(IP Multimedia CN subsystem) comprises of all CN elements for the provision of IP multimedia applications over IP multimedia sessions
IP multimedia session:
set of multimedia senders and receivers and the data streams flowing from senders to receivers. IP multimedia sessions are supported by the IP multimedia CN Subsystem and are enabled by IP connectivity bearers (e.g. GPRS as a bearer). A user may invoke concurrent IP multimedia sessions.
Stateful proxy:
logical entity that maintains state information at least for the duration of a SIP transaction, see RFC 3261 [3]
For the purposes of the present document, the following abbreviations apply:
BGCF
Breakout Gateway Control Function
CN
Core Network
COPS
Common Open Policy Service
CSCF
Call Session Control Function
DHCP
Dynamic Host Configuration Protocol
DNS
Domain Name System
FQDN
Fully-Qualified Domain Name
G-MSC
Gateway Mobile Switching Centre
GGSN
Gateway GPRS Support Node
GPRS
General Packet Radio Service
HSS
Home Subscriber Server
I-CSCF
Interrogating-CSCF
IM
IP Multimedia
IP
Internet Protocol
IPv6
IP version 6
MEGACO
MEdia GAteway COntrol
MGCF
Media Gateway Control Function
MGW
Media Gateway
P-CSCF
Proxy-CSCF
PDF
Policy Decision Function
PDP
Packet Data Protocol
PSTN
Public Switched Telephone Network
QoS
Quality of Service
SBLP
Service-based local policy
S-CSCF
Serving-CSCF
SDP
Session Description Protocol
SGSN
Serving GPRS Support Node
SIP
Session Initiation Protocol
SS7
Signalling system no. 7
UAC
User Agent Client
UAS
User Agent Server
UE
User Equipment
URI
Uniform Resource Identifier
UMTS
Universal Mobile Telecommunications System
USIM
User Service Identity Module