(SIP CLIENT) —> (Our Asterisk PBX) —> Nokia MGW —> MSC —> (SS7/PSTN cloud) —> handset1 --> handset2 —> handset3 -->
What we are looking for is basically for Asterisk to detect outbound calls it made that if the call further down the line if it has been redirected. For now we don’t need to do anything with it but we need to know for certain who it has been redirected to and how many times. This is for fraud prevention. We need certain calls to be restricted to being forwarded or find out after the fact if its been forward for our security team.
In our ISUP SS7 trace, we do see the redirected number under the field “Unknown Parameter (0xc):”. In ISUP ITU
[Jul 6 17:04:31] VERBOSE[29457] chan_dahdi.c: CIC: 1
[Jul 6 17:04:31] VERBOSE[29457] chan_dahdi.c: Message Type: ACM
[Jul 6 17:04:31] VERBOSE[29457] chan_dahdi.c: --OPTIONAL PARMS–
[Jul 6 17:04:31] VERBOSE[29457] chan_dahdi.c: Generic Notification Indication:
[Jul 6 17:04:31] VERBOSE[29457] chan_dahdi.c: [ 2c 01 fb ]
[Jul 6 17:04:31] VERBOSE[29457] chan_dahdi.c: Unknown Parameter (0xc):
[Jul 6 17:04:31] VERBOSE[29457] chan_dahdi.c: [ 04 10 44 77 18 61 30 23 ]
[Jul 6 17:04:31] VERBOSE[29457] chan_dahdi.c: Unknown Parameter (0x36):
[Jul 6 17:04:31] VERBOSE[29457] chan_dahdi.c: [ 19 ]
[Jul 6 17:04:31] VERBOSE[29457] chan_dahdi.c: Parameter Compatibility Information:
[Jul 6 17:04:31] VERBOSE[29457] chan_dahdi.c: [ 39 04 2c c0 36 c0 ]
We see the redirected number back in the ACM but its not very well presented. Will a DAHDI PCAP dump be any better if we install the patch to allow for pcap dump?
Second, in Asterisk 1.8 (wiki.asterisk.org/wiki/display/ … anfunction) There are redirection counter variables, can I artificially inflate these to force switches down the line to stop the call because per ITU rules, a call can be only redirected maximum of 5 times?