SIP / ISUP interconnection
Gonzalo Camarillo
Gonzalo.Camarillo@ericsson.com
ASRL
Advanced Signalling Research Lab.
Gonzalo Camarillo
Atlanta September 28th, 1999
Fall ‘99 VON
VON protocols - SIP
Advanced Signalling Research Lab.
Telephone Services
•GSTN (General Switched Telephone Network)
•IP Telephony
IP Telephony
Gonzalo Camarillo
Atlanta September 28th, 1999
GSTN
Fall ‘99 VON
VON protocols - SIP
Advanced Signalling Research Lab.
Contents
• Brief SS7 introduction (architecture)
• Gateway architecture ( SG, MGC, MG )
• ISUP - SIP interworking issues and proposed
solutions
Gonzalo Camarillo
Atlanta September 28th, 1999
Fall ‘99 VON
VON protocols - SIP
Advanced Signalling Research Lab.
Different architectures
GSTN architecture:
Intelligence in the network
Dumb terminals
SIP architecture:
Move the intelligence to the edge
Gonzalo Camarillo
Atlanta September 28th, 1999
Fall ‘99 VON
VON protocols - SIP
Advanced Signalling Research Lab.
Signalling in GSTN
Signalling in the network (between switches)
User to network signalling
DSS 1
Gonzalo Camarillo
Atlanta September 28th, 1999
ISUP
Fall ‘99 VON
VON protocols - SIP
DSS 1
Advanced Signalling Research Lab.
DSS-1
Q. 931
Protocol between the user and the network
Much simpler than ISUP.
Q. 921
Handles the transport of the messages
Gonzalo Camarillo
Atlanta September 28th, 1999
Fall ‘99 VON
VON protocols - SIP
Advanced Signalling Research Lab.
Signalling in GSTN
SS7 (System Signalling No. 7)
Level
TCAP
ISUP
TUP
4
SCCP
3
2
MTP
1
Gonzalo Camarillo
Atlanta September 28th, 1999
Fall ‘99 VON
VON protocols - SIP
Advanced Signalling Research Lab.
General ISUP<->SIP Conversion
Voice Stream
Signalling
SG
SIP Server
STP
ISUP/MTP
ISUP/IP
SIP
SIP
MGC
IP network
SIP
MGCP
SS7
SIP Client
MG
DSS 1
E1/T1
Gonzalo Camarillo
Atlanta September 28th, 1999
RTP
Fall ‘99 VON
VON protocols - SIP
Advanced Signalling Research Lab.
Architecture of the distributed gateway
ISUP
Signalling Gateway
IP side
ISUP/IP
GSTN side
Media Gateway Controller
SIP
MGCP
Voice stream
Gonzalo Camarillo
Atlanta September 28th, 1999
Media Gateway
Fall ‘99 VON
VON protocols - SIP
Voice stream
Advanced Signalling Research Lab.
Signalling Gateway
Function:
• To find the appropriate media gateway controller
Signalling GW
ISUP
ISUP/IP
ISUP/IP
ISUP/IP
MGC
MGCP
Gonzalo Camarillo
Atlanta September 28th, 1999
SIP MGCP
ISUP/IP
MGC
SIP
MGC
MGCP
Fall ‘99 VON
VON protocols - SIP
MGC
SIP MGCP
SIP
Advanced Signalling Research Lab.
Media Gateway
Mapping between different voice formats
Control
Protocol
GSTN
Gonzalo Camarillo
Atlanta September 28th, 1999
RTP
Fall ‘99 VON
VON protocols - SIP
Advanced Signalling Research Lab.
Media Gateway Controller for
distributed
Media Gateways
Functions
• Actual mapping between protocols (ISUP-SIP)
• Control the Media Gateway/s
• Authentication, Authorization and Accounting (AAA)
Gonzalo Camarillo
Atlanta September 28th, 1999
Fall ‘99 VON
VON protocols - SIP
Advanced Signalling Research Lab.
Experiences implementing
ISUP to SIP mapping
• Different flavours of ISUP (message flow)
• Overlap signalling (SAMs)
• In band announcements and ring-back tone
• ISUP transparency
• Billing in forwarding situations
• Tracing calls (malicious, SOS)
Gonzalo Camarillo
Atlanta September 28th, 1999
Fall ‘99 VON
VON protocols - SIP
Advanced Signalling Research Lab.
Different message flows
ITU ISUP message exchange during a call
Local
Exchange
Local
Exchange
IAM
ACM
CPG
ANM
Voice Transfer
REL
RLC
ANSI ISUP: CPG before ACM
Gonzalo Camarillo
Atlanta September 28th, 1999
Fall ‘99 VON
VON protocols - SIP
Advanced Signalling Research Lab.
Overlap signalling (SAMs)
European phone numbers does not have a fixed length.
Example:
+358
9
299
Finland Helsinki Ericsson
+358
9
299
Finland Helsinki Ericsson
1
Front desk
3371
Camarillo’s
The ingress gateway cannot know when the number is
complete.
Gonzalo Camarillo
Atlanta September 28th, 1999
Fall ‘99 VON
VON protocols - SIP
Advanced Signalling Research Lab.
Proposed solution
Ingress gateway waits for SAMs with more digits
a certain amount of time.
• Timer = 0
Heavy signalling traffic may be generated
• Timer = 5 secs ( inter-digit timeout)
User is not that patient
Gonzalo Camarillo
Atlanta September 28th, 1999
Fall ‘99 VON
VON protocols - SIP
Advanced Signalling Research Lab.
In-band announcements and
ring-back tones
•‘Your call is being forwarded to an automatic voice mail’
• Ring-back tone
• Busy tone
Proposed solution: 183 SIP response
SIP Client
MG
DSS 1
E1/T1
Gonzalo Camarillo
Atlanta September 28th, 1999
RTP
Fall ‘99 VON
VON protocols - SIP
Advanced Signalling Research Lab.
ISUP transparency
(SIP bridging)
Voice Stream
SG
Signalling
SG
ISUP/MTP
ISUP/MTP
ISUP/IP
ISUP/IP
SIP
STP
MGC
MGC
STP
IP network
MGCP
MGCP
E1/T1
RTP
MG
Gonzalo Camarillo
Atlanta September 28th, 1999
E1/T1
MG
Fall ‘99 VON
VON protocols - SIP
Advanced Signalling Research Lab.
ISUP transparecy
( SIP bridging)
ISUP messages in SIP bodies (MIME),
SIP INFO method, reliable 1xx responses ...
Trusted parties, confidentiality, ISUP flavours...
Gonzalo Camarillo
Atlanta September 28th, 1999
Fall ‘99 VON
VON protocols - SIP
Advanced Signalling Research Lab.
Billing
scenarious
Isabel calls from Spain to my GSM mobile:
+358 40 702 35 35 (Finland’s international prefix)
Isabel pays the call leg Spain-Finland
I pay the call leg Finland-Atlanta
SIP is end to end … where are the call legs??
Gonzalo Camarillo
Atlanta September 28th, 1999
Fall ‘99 VON
VON protocols - SIP
Advanced Signalling Research Lab.
Tracing calls
• SOS services ( physically closest center )
• Malicious calls
An IP address or a SIP URL do not give any useful
information for catching the “bad guys”.
Gonzalo Camarillo
Atlanta September 28th, 1999
Fall ‘99 VON
VON protocols - SIP
Advanced Signalling Research Lab.
Further information
IETF internet drafts ( www.ietf.org )
• draft-ietf-sigtran-mime-isup-00.txt
• draft-ietf-mmusic-sip-multipart-00.txt
• draft-zimmerer-mmusic-sip-isup-mime-00.txt
• draft-ietf-mmusic-sip-info-method-01.txt
• draft-ietf-mmusic-sip-100rel-00.txt
• draft-roach-mmusic-sip-provisional-media-00.txt
• draft-donovan-mmusic-183-00.txt
• draft-roach-mmusic-sip-pstn-require-header-00.txt
• draf-zimmerer-mmusic-sip-bcp-t-00.txt
• draft-roach-sip-isup-parameters-00.txt
• draft-camarillo-mmusic-sip-isup-bcp.txt
Gonzalo Camarillo
Atlanta September 28th, 1999
Fall ‘99 VON
VON protocols - SIP
Advanced Signalling Research Lab.