Control and monitoring for fast millimeter-wave link using out-of-band wireless channel

A server that allows a client to more efficiently download data, which comprises:

• means for transmitting test packets to said client, said test packets including a first test packet of a predetermined length transmitted via a first communication line of a relatively low communication speed, and a second test packet of a predetermined length transmitted via a second communication line of a relatively high communication speed;
• means for receiving a first period and a second period transmitted from said client as information on a test result, said first period being from start to completion of reception of said first test packet, said second period being from start to completion of reception of said second test packet;
• means for starting transmission of data packets corresponding to said length of said second test packet to said client via said second communication line;
• and
• means for transmitting, at a point when a latency difference has passed since said start of transmitting said data packets via said second communication line, check packets corresponding to said length of said first test packet to said client via said first communication line.