During test international call find out that call to several country is not delivered. For example, to Belarus, Armenia, Estonia ect.
1) Find out that International gateway release call because of non-standard format of called number
2) Check call flow and find out that number change on ATS.
For successfull call ATS send INVITE with following header:
invite tel:+86-75528560999 sip/2.0
For unsuccessfull call ats send invite with following header:
invite tel:00375175100000 sip/2.0
But should be following format for all international calls:
invite tel:+CC-xxxxxxxxxxx sip/2.0
3) After checking ATS configuration we found that there is not configuration of country code for several country. And calls can't be delivered to these country.
After adding CC for Belarus and other countries calls are established successfully:
add ncode: nac=k'375, nn="belarus";
1) Check signalling between IMS network and International gateway.
2) Check intra-IMS signalling.
3) Check ATS configuration.
This solution is applicable for IMS 8.0, IMS 8.1 and IMS 8.2.
See for batch file with all country code in attachment.