AudioCodes Mediant 4000 SBC, User Manual

Page: 633 / 1037

CHAPTER 28 Advanced SBC Features
Mediant 4000 SBC | User's Manual
The SIP-I sends calls, originating from the SS7 network, to the SIP network by adding ISUP
messaging in the SIP INVITE message body. The device can receive such a message from the
SIP-I and remove the ISUP information before forwarding the call to the SIP endpoint. In the other
direction, the device can receive a SIP INVITE message that has no ISUP information and before
forwarding it to the SIP-I endpoint, create a SIP-I message by adding ISUP information in the SIP
body. For SIP-I to SIP-I calls, the device can pass ISUP data transparently between the endpoints.
For the interworking process, the device maps between ISUP data (including cause codes) and
SIP headers. For example, the E.164 number in the Request-URI of the outgoing SIP INVITE is
mapped to the Called Party Number parameter of the IAM message, and the From header of the
outgoing INVITE is mapped to the Calling Party Number parameter of the IAM message.
The ISUP data is included in SIP messages using the Multipurpose Internet Mail Extensions
(MIME) body part, for example (some headers have been removed for simplicity):
INVITE sip:1774567@172.20.1.177;user=phone SIP/2.0
Via: SIP/2.0/UDP 172.20.73.230:5060;branch=z9hG4bK.iI
...
Accept: application/sdp, application/isup, applicatio
Content-Type: multipart/mixed; boundary=unique-bounda
MIME-Version: 1.0
Content-Length: 350
...
Content-Type: application/isup; version=FTSSURI; base
Content-Disposition: signal; handling=required
01 00 40 01 0a 02 02 08 06 83 10 71 47 65 07 08
01 00 00
--unique-boundary-1—
D6 SIP-T ISUP/IAM (Initial address message)
(--) len:-- >> Nature of connection indicators
Oct 1 : ---0---- Echo ctrl = Half echo not included
----00-- Cont. check = Not required
------00 Satellite = No circuit
(--) len:-- >> Forward call indicators
Oct 1 : 01------ ISUP pref. = Not req. all the way
--0----- ISUP indic. = Not used all the way
---0---- End-end inf = Not available
----0--- Interwork. = Not encountered
-----00- Method. ind = No method available
-------0 Call indic. = as National call
Oct 2 : -----00- SCCP method = No indication
- 600 -