Hi Thank you for your reply about DSL mtu Now I have question about internet cable connection. ls it same as DSL? I tested it in my friend cable connection. 1470 is fine but 1480 is problem. Why it needs header in cable connection also? C:\Documents and Settings\deric>ping yahoo.com -f -l 1470 Pinging yahoo.com [98.137.149.56] with 1470 bytes of data: Reply from 98.137.149.56: bytes=1470 time=96ms TTL=50 Reply from 98.137.149.56: bytes=1470 time=91ms TTL=50 Reply from 98.137.149.56: bytes=1470 time=92ms TTL=50 Reply from 98.137.149.56: bytes=1470 time=89ms TTL=50 Ping statistics for 98.137.149.56: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 89ms, Maximum = 96ms, Average = 92ms C:\Documents and Settings\deric>ping yahoo.com -f -l 1480 Pinging yahoo.com [98.137.149.56] with 1480 bytes of data: Packet needs to be fragmented but DF set. Packet needs to be fragmented but DF set. Packet needs to be fragmented but DF set. Packet needs to be fragmented but DF set. Ping statistics for 98.137.149.56: Packets: Sent = 4, Received = 0, Lost = 4 (100% loss), Thank you for your help