If you are experiencing:
- Dropped calls
- One-way audio (ie. you can hear the contact but they cannot hear you, or vice-versa)
- Inability to receive incoming calls
... Your VoIP router may have SIP ALG (application-level gateway) enabled on your router and most likely needs to be turned off. To determine if SIP ALG is enabled on your router contact your VoIP provider (for VanillaSoft VoIP customers, contact ConnectMeVoice at 1-800-743-1208), and they should be able to determine if SIP ALG is enabled on your router.
If your VoIP provider confirms that SIP ALG is enabled, you will need to turn that feature in your router off. VanillaSoft is unable to log in to your router and make these changes, but the information is available online. Find out the make and model of your router, and contact the router manufacturer for instructions on how to turn SIP ALG off. If your router is provided by your ISP, please contact your ISP as they will be able to help you turn this setting off.
What is SIP ALG?
Many of today's commercial routers implement a SIP ALG (application-level gateway), with this feature being enabled by default. Router manufacturers add this feature in with the intent of increasing VoIP quality, but the fact is that many routers’ ALG implementations are faulty and actually break SIP. SIP ALG modifies the SIP packets in unexpected ways, corrupting them and making them unreadable. For more info go to: http://www.voip-info.org/wiki/view/Routers+SIP+ALG