Hi All,   I gave interview at Cisco  for IPT engineer,and the first question they asked about IP Phone registration process,and i answered in detail as per my knowledge,But i dont think the were looking for that answer, Can anybody help me with the i...

Hi All,   My question is ,what are the possible cause if Phone A is calling Phone B and hear a busy tone in a multi-site with centralized deployment and also in multi-site with distributed deployment,   Thanks in advance