PING www.skbooks.co.kr (18.239.18.71) 56(84) bytes of data.
64 bytes from server-18-239-18-71.ams58.r.cloudfront.net (18.239.18.71): icmp_seq=1
ttl=251 time=5.89 ms
64 bytes from server-18-239-18-71.ams58.r.cloudfront.net (18.239.18.71): icmp_seq=2
ttl=251 time=3.96 ms
64 bytes from server-18-239-18-71.ams58.r.cloudfront.net (18.239.18.71): icmp_seq=3
ttl=251 time=3.95 ms

--- www.skbooks.co.kr ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2001ms
rtt min/avg/max/mdev = 3.953/4.603/5.897/0.917 ms