This paper describes the integration of the presence management service into existing IP Multimedia Subsystem (IMS) laboratory infrastructures. Both laboratories – NGNlab in Bratislava and the laboratory in Leipzig – use the Fraunhofer OpenIMS as core components for their testing IMS environment (i.e. Call Session Control Functions (CSCF), Home Subscriber Server (HSS)). The virtualization of these components will be described in this paper. Furthermore, the layer 3 interconnection and hence the possibility to share different applications between the locations will be discussed. The presence management service has been deployed in a state where it is ready to be used with current IMS clients, for both presence information sharing via the Session Initiation Protocol (SIP) and user authorization via Extended Markup Language (XML) Configuration Access Protocol (XCAP). Presented at ONIT 2009 in Berlin, Germany.

1. Presence service integration
using interconnected IP
Multimedia Core Networks
Eugen Mikóczý, Sebastian Schumann
Slovak University of Technology, Bratislava
Stephan Massner, Michael Maruschke
Hochschule für Telekommunikation, Leipzig

2. Outline
• Infrastructure
• Interconnection
• Presence service in the IMS
• Deployment
• Current state
• Future use cases

3. Infrastructure
• Bratislava
– ngnlab.eu: Virtualized environment for
educational and research purposes
– OpenIMS testbed installed and integrated with
services (e.g. presence)
• Leipzig
– NGN test and research lab with OpenIMS
• Interconnected infrastructure via secured
OpenVPN channel

4. Testbed in Bratislava
SIPI-CSCFP-CSCF
S-CSCF
Signaling core
Support systems
HSS
NGN
ASF
NGN NGN NGN NGN
ASF ASF ASF ASF
Proxy
Application layer
XDMS
(voice)(conf.)(IPTV)(presence)
• Logically separated
HW machine
• Xen virtualization
• All components via
NAT behind proxy
• Different VLANs
• VPN client on
proxy connects to
Leipzig GW

5. Interconnection
Media
Data
Signalling
Data
Application
Data
AS
UE
AS
UE
GWGW
IMS Testbed STUIMS Testbed HfTL
Public
Internet
VPN Tunel
Core IMS
#B
Core IMS
#A
HfTL - Hochschule f?r Telekommunikation Leipzig (Germany)
Legend:
GW - Gateway (for Interconnection)
AS - Application Server
UE - User Equipment STU - Slovak University of Technology Bratislava (Slovakia)
Interconnection - Current status

6. Interconnection ctd.
Legend: AS - Application Server
VPN Tunel
Media
Data
Signalling
Data
Application
Data
AS
GWCore IMS
Network
Core Transport
Steps from plain to standardized Interconnection
Establishment of
a shared VPN-
interconnection
between two
different and
separate located
IMS-based
Multimedia
Networks
Step 1)

7. Interconnection ctd.
Legend:
IBCF - Interconnection Border Control Function
AS - Application Server
VPN Tunel
Media
Data
Signalling
Data
Application
Data
AS
GWIBCFCore IMS
Network
Core Transport
Steps from plain to standardized Interconnection
Establishment of
a standardized
interconnection
in the signalling
layer using the
IBCF to connect
two IMS-based
Multimedia
Networks
Step 2)

8. Interconnection ctd.
Legend:
IBCF - Interconnection Border Control Function
AS - Application Server
SPDF - Service-based Policy Decision Fcuntion
IBGF - Interconnection Border Gateway Function
VPN Tunel
Media
Data
Signalling
Data
Application
Data
AS
GWIBCF
SPDF
IBGF
Core IMS
Network
Core Transport
Steps from plain to standardized Interconnection
Establishment of
a standardized
interconnection
in the signalling
layer using the
IBCF and in the
transport layer
using the IBGF to
connect two
IMS-based
Multimedia
Networks
Step 3)

9. Interconnection ctd.
Application
Data
Media
Data
Signalling
Data
ANGF - Access Network Gateway Function
UE - User Equipment
AS - Application Server
Legend:
RACS - Ressource and Admission Control Subsystem
IBGF - Interconnection Border Gateway Function
NASS - Network Attachment Subsystem P-CSCF - Proxy Call Session Control Function
IBCF - Interconnection Border Gateway Function
IMS Testbed
Network
IP Transport
IBGF
RACS NASS
ANGF
Core IMS P-
CSCF
IBCF
AS
UE
Ut
Gm
Ut
Gm
Ic
Iz
Network
IP Transport
IBGF
RACSNASS
ANGF
Core IMSP-
CSCF
IBCF
AS
UE
Slovak University of
TechnologyTelekommunikation Leipzig
Hochschule f?r
IMS Testbed
Future view of Interconnection possibilities
Data
Media
Data
Media

10. Presence service in the IMS
• Proxy only L3 outbound proxy for UE
• P-CSCF is logical end-point (L7) for
connections
• P-CSCF assigns P-Asserted-Identity (PAI)
header that presence server (PS) will trust
later
• S-CSCF triggers presence related SIP
message to be relayed towards PS

11. Presence service in the IMS ctd.
• Initial filter criteria (IFC) enables routing
to application server, e.g. PS
• Filter: Event: presence, presence.winfo
• Both domains (.sk .de) forward to one PS
• PS trusts PAI header from both domains
(otherwise also challenging possible)

12. Service Profile
User Profile
Service Profile
Includes information about service access and
dependencies to user registration state
and service availibility.
Each service profile can be specified for a
single user or shared by different users by
linking the service profile.

13. Service Profile ctd.
User Profile
Service Profile
Indicator: registered/unregistered/independend
The Indicator describe the dependency to user
registration state.
Three different states will be differ:
- registered (user is registered)
- unregistered (user is not registered)
- independend (user registered or not)

14. Triggering
User Profile
Filter: Trigger Point + AS Information
Service Profile
Indicator: registered/unregistered/independend
Filter describe an term including information
about trigger point and application server
access data belong the service profile.
An trigger point is a logical expression
including sip message parts and matching
expressionsaccording the service.

15. Triggering ctd.
User Profile
available
if AS isn't
Proceedings
SIP-URILogical expression:
CNF: ( A or B ) and C
DNF: ( A and B ) or C
Filter: Trigger Point + AS Information
Service Profile
Indicator: registered/unregistered/independend
Requested URI
Method
header
Session case
SDP line
matches/
equals/
is one of
Service Point Trigger:

16. Deployment
• OpenIMS CSCFs and HSS from FOKUS
Fraunhofer
– P-CSCF can be reached via proxy externally
– Other components on one VLAN
• OpenSIPS as PS, configured to work as
IMS ASF
– PS can be reached via S-CSCF, separate VLAN
• OpenXCAP as XDMS, integrated with PS
– XDMS can be reached via proxy externally

17. Current state
• L3 secured interconnection
• ASF sharing not via standardized IMS
procedures but simple direct access
• Interconnection proven to work (no
significant packet delay, security verified)
• After the base is proven, future steps
towards standardized interconnection can
be taken

18. Future use cases
• IBCF in signaling layer to interconnect IMS
core networks
• IBCF in signaling and IBGF in transport
layer to interconnect the networks
• Integrate also IMS interconnected call
scenarios acc. standards and perform tests

19. Thank you.