Hello Satish,
There are many reasons that can cause this issue, one of them is the speed and duplex configured on the interface.Make sure that they are hard coded to what you want. (For ex Full-Duplex and 100 Mbps speed).
In order to troubleshoot this effectivly, please attach the output of the "show tech command.
Also, if possible, connect a PC to the inside interface and an FTP server on the outside interface. Then try to run some packet captures on both interfaces. Afterwards, attach the pcap files.