By the way in some countries/regions filtering or blocking ports is either illegal or in violation of the terms of agreement. I had once experienced port filtering from an ISP which generally allowed VoIP but were blocking the SIP signaling ports to one particular VSP, it seems they had beef and no registration could occur. I traced the problem and luckily the law was on my side. I prepared and filed a rigorous complaint and I told them they have 24 hours to rectify or I will slap them with a law suit. In less than two hours the CEO of the company called me personally to apologize and inform me that all filtering had been completely removed.
