In order to have a better support of the Swisscom Business Connect VOIP service, it is necessary to adapt the configuration of a ZyXEL ZyWALL (USG) firewall. All SIP ALG functionalities must be disabled, and the UDP timeouts must be adapted to 180 seconds.
The script BusinessConnect.zysh will do these adjustments automatically. in order to apply the script, go in the menu Maintenance / File Manager / Shell Script, upload the file BusinessConnect.zysh, and finally click on Apply for this file.