I have two ubuntu boxes one in US and another in India and have a 12 Mbps connection. when i copy from using scp the transfer rate is 50KB/s is there a way to increase the speed. these boxes have 4GB ram and a good processor
Your problem here is not with the bandwidth, but latency. The TCP overhead on such a link will cause all sorts of link speed troubles, which you're experiencing. TCP and by proxy SCP/SSH was never meant to work on this kind of link fast, as it's upmost priority is security and reliability of the transfer stream.
There are multiple solutions to the issue.