It's really a big problem for us who are the VoIP ITSPs, wholesalers, distributors, retailers even the end-users.Their business is declined and the user is dissatisfied.
However,it's also a big opportunity for earn client. The answer is VGCP, which is created for this issue, and can bypass the blocking with good voice quality.
For more details pls refer to SpeedVoIP - VoIP Blocking, VPN, Encryption, SIP Adapter, ATA, Gateway

Lynn
Email: lynn@speed-voip.com
MSN: svoipsales@hotmail.com
Skype: svoipsales
Yahoo: speedvoip@yahoo.com
Website: SpeedVoIP - VoIP Blocking, VPN, Encryption, SIP Adapter, ATA, Gateway