agenda introduction to 3gpp introduction to sip ip multimedia subsystem service routing in ims...
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Agenda
• Introduction to 3GPP
• Introduction to SIP
• IP Multimedia Subsystem
• Service Routing in IMS
• Implementation
• Conclusions
Service routing in 3GPP IP Multimedia Subsystem
Teemu Jalava
Supervisor: Raimo Kantola
Instructor: M.Sc. Markus Isomäki, Nokia Research Center
3rd Generation Partnership Project (3GPP)
• The 3rd Generation Partnership Project (3GPP) is a collaboration agreement that brings together a number of telecommunications standards bodies and telecommunications companies.
• Release ’99 was renamed Release 3
• Release 4 was out March 2001- IP network
• Release 5 should be ready in summer 2002- IP multimedia
• Release 6- All IP network
3GPP Network Architecture
DOCUMENTTYPE
TypeUnitOrDepartmentHereTypeYourNameHere TypeDateHere
Radio Access Network Core Network
IuUu
End userterminal
AS
Session Initiation Protocol (SIP)
• Creation, modification and termination of multimedia sessions
• RCF 2543 -> RCF 3261
• Request - Reply based transactions
• Easy to make new extensions
• ASCII based, clear text, similar to HTTP
• Uses UDP or TCP
• URL addressing
• sip:teemu.jalava@nokia.com
Proxy Client 2Client 1
INVITEINVITE
100 Trying
180 Ringing
180 Ringing
200 OK
200 OK
ACK
ACK
Media streams
BYE
BYE
200 OK
200 OK
SIP sample packet
INVITE sip:bob@brown.com SIP/2.0Via: SIP/2.0/UDP 130.23.16.19:32746 ;branch=z9hG4bKCabU9qqUgvZDFrom: <sip:alice@wonder.net>;tag=uce5728c0To: <sip:bob@brown.com>Call-ID: f24793c0-c9a3-11d5-c48d-14064620c566CSeq: 4 INVITEContact: <sip:alice@130.23.16.19:32746>Content-Type: application/sdpContent-Length: 143
v=0o=alice 1756606023 1 IN IP4 130.23.16.19s=-c=IN IP4 130.23.16.19m=audio 5004 RTP/AVP 8 0a=rtpmap:8 PCMA/8000a=rtpmap:0 PCMU/8000
Method name Request URI
Headers
Messagepayload
Emptyline
First line
SIP Routing
• SIP proxy takes care of user location resolving
• teemu.jalava@nokia.com -> user1@130.233.20.40
• using registrar, DNS (ENUM in case of tel URL) or other means
• DNS Service Resource Records (SRV RR) can be used to locate a SIP proxy in an other domain
• via header is needed to ensure packets route the same way back
• record-route header is needed is sertain proxies need to be in the routing path
IP Multimedia Subsystem (IMS)
UA P-CSCF I-CSCF S-CSCF
Gm Mw Mw
SLF
Dx Cx
HSS AS
Cx
SIP SIPSIP
SIPDiameter
Sh
Visited Domain
Home Domain
ISC
HomeSubscriber
Server ApclicationServer
SubscriptionLocation Function
Diameter
Call State Control Function (CSCF)
• First contact point
• Provides provicy control and QoS authorization
• Local services, like emergency calls and local numbering
Proxy-CSCF
• Accesspoint to domain
• Hides topology and configuration
Interrogating-CSCF
• Session control services
• Registration, AS usage, charging, etc
Serving-CSCF
(User Agent)
IMS Session overview
P-CSCF
I-CSCF
UA2’s visited network
UA1
UA2
UA1’s home network
S-CSCF
I-CSCF
P-CSCF
S-CSCF
I-CSCF
I-CSCF
(optional)
UA2’s home network
UA1's visited network
Application serversRoles:
• SIP proxy
• redirect server
• Back-to-back-user-agent (B2BUA)
• User Agent
How:
• Forking
• SUBSCRIBE - NOTIFY
• MESSAGE
• Third party call control
Using:• Call Processing Lanquage (CPL)
• SIP Common Gateway Interface (CGI)
• SIP Servets
What:• Presence
• Instant Messaging
• Group services
Application example: Presence
• Presence enables user to express willingness and availability to communicate
• Can be used with phonebook to make a "buddy list"
• Presence updates with REGISTER method
• Presence download with SUBSCRIBE - NOTIFY
Example of service routingExample of service routing
P-CSCF S-CSCF
AS 1
AS 2
AS 3
1. INVITE 2. INVITE
3. INVIT
E
4. INVIT
E
5. INVITE6. INVITE
7. IN
VITE
Terminating network
S-CSCF routing decisions
• Based of Filter Criteria downloaded from Home Subscriber Server (HSS) at user registration
• User profile
• Filter Criteria• Address of the Application Server to be contacted.
• Priority
• Trigger Points (method, presence or apsence of any header, header content, etc)
• Default Handling
• Optional Service Information
Implementation
• Proof of concept work
• S-CSCF from a SIP proxy• Adding filtering
• Integrated user profile
• Configuring user profile
• Testing with network containing Presence AS, redirection AS and SIP-SMSGW
Conclusions
• SIP based services are easy to make and integrate to the IMS network
• Configuration is easy
• Scalable sollution, AS and S-CSCF duplication
• Release 5 has been delayed from jan 2002 to june 2002, some features have been postponed to Release 6
• Some pressure from 3GPP to IETF to finalize new SIP RFC and SIP compression
These might have some impact to service routing issues
• Questions?
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