Transcript SIP and the application of SIP as used in 3GPP

SIP and the application of SIP as
used in 3GPP
Keith Drage - Lucent Technologies
Overview of the 3GPP IM CN
subsystem architecture
• Independent of the access mechanism
• Mobility provided by underlying access
mechanism
• Functional entities use IPv6
• Functionality apportioned between visited
network and home network
• Home network control of services
Overall 3GPP architecture
Home
Network
Domain
[Zu]
Cu
Uu
GPRS
IM CN
subsystem
Iu
[Yu]
Serving
Network
Domain
USIM
Domain
Mobile
Equipment
Domain
User Equipment
Domain
Access
Network
Domain
Transit
Network
Domain
Core
Network
Domain
Infrastructure
Domain
GPRS - user plane versus
transport plane
User IPv6
GGSN
Terminal
UTRAN
Application
Server
Core Network
Transport IPv6
– User and transport planes are completely independent, i.e. the transport plane
can run on a different IP version than the user plane
– UTRAN and Core Network transport can also run on different IP versions
GPRS - Transport of user IP
packets in UMTS
User IPv6 (PDP type IPv6)
UTRAN
Terminal
Radio Bearer
SGSN
GTP-U
GGSN
Application
Server
GTP-U
IP packets to/from the terminal are tunneled through the UMTS network, they
are not routed directly at the IP level.
3GPP requires multiple
outbound proxies
REG
UA
200 OK
REG
PCSCF
200 OK
REG
ICSCF
200 OK
SCSCF
User
Visited
Home
Home
equipment
network
network
network
P-CSCF - Proxy CSCF (Call Session Control Function). The terminals point of contact
in the visited network after registration. Point where network places constraint on the
bearer.
I-CSCF - Interrogating-CSCF. Responsible for finding the S-CSCF at registration. May
also perform hiding of the S-CSCF network architecture.
S-CSCF - Serving-CSCF. Responsible for identifying user’s service privileges.
Responsible for selecting access to home network application server (service platform)
and for providing access to that server.
Example allocation of functional
entities - mobile to mobile
User A
A’s visited network
GPRS
P-CSCF
Required on
A’s home network
registration,
optional on
sessiion establish
S-CSCF
I-CSCF
I-CSCF
Optional
User B
I-CSCF
GPRS
I-CSCF
P-CSCF
S-CSCF
B’s home network
Required on
registration,
optional on
sessiion establish
B’s visited network
Example allocation of functional
entities - PSTN to mobile
MGW
User B
MGCF
GPRS
I-CSCF
P-CSCF
S-CSCF
B’s home network
Required on
registration,
optional on
sessiion establish
B’s visited network
Example allocation of functional
entities - mobile to PSTN
User A
A’s visited network
Required on
A’s home network
registration,
optional on
sessiion establish
S-CSCF
GPRS
P-CSCF
I-CSCF
BGCF
BGCF
MGW
SGW
MGCF
Breakout network
Provision of services
SIP Application
Server
Sh
ISC
Sh
Cx
HSS
S-CSCF
ISC
OSA Service
Capability Server
(SCS)
OSA API
ISC
IM SSF
MAP
ISC interface runs
the SIP protocol
CAP
CAMEL Service
Environment
OSA
Application
Server
Summary of architecture
SLF
HSS
Dx
Gm
UA
Mw
P-CSCF
AS
Cx
Cx
Mw
I-CSCF
S-CSCF
Mg
Mg
Mg
BCGF
MGCF
Mc
MGW
Key 3GPP documents and
their location on 3GPP servers
• TS 23.228: "3rd GPP; Technical Specification Group Services and
System Aspects; IP Multimedia (IM) Subsystem - Stage 2".
• TS 24.228: "3rd GPP; Technical Specification Group Core Network;
Signalling flows for the IP multimedia call control based on SIP and
SDP".
• TS 24.229: "3rd GPP; Technical Specification Group Core Network;
IP Multimedia Call Control Protocol based on SIP and SDP".
• TS 23.218: "3rd GPP; Technical Specification Group Core Network;
IP Multimedia (IM) Session Handling; IP Multimedia (IM) call model”
These drafts can be found at the 3gpp web site either at:
• ftp://ftp.3gpp.org/Specs/Latest_drafts/
• ftp://ftp.3gpp.org/Specs/2001-06/Rel-5
depending on the status of the document
Issues for SIP
Multiple outbound proxies path
Insert
P-CSCF
address
REG
UA
200 OK
Add
I-CSCF
address
REG
PCSCF
Store
S-CSCF and
I-CSCF addresses
200 OK
Store
P-CSCF and
I-CSCF addresses
REG
ICSCF
200 OK
SCSCF
Add
S-CSCF
address
Compression
• Efficient use of bandwidth is required on the radio interface.
• Will be applied to both the media streams (header compression or
removal) and to the signalling bearers.
• Compression / decompression of SIP will be performed by the UE and
the P-CSCF.
• These entities will also perform integrity protection on the signalling
bearer.
Other issues still in discussion at
requirements level
• Emergency calls, and support of location based services, requires the
transfer of location information (needs GEOPRIV to complete).
• Interworking with external SIP environments requires transcoding
support. Default codec for 3GPP is the AMR codec.
• There are functional entities which have not been shown in these slides
which will require SIP support, e.g. MRF.
Questions