PING skbooks.co.kr (18.239.18.128) 56(84) bytes of data.
64 bytes from server-18-239-18-128.ams58.r.cloudfront.net (18.239.18.128): icmp_seq=1
ttl=251 time=4.74 ms
64 bytes from server-18-239-18-128.ams58.r.cloudfront.net (18.239.18.128): icmp_seq=2
ttl=251 time=4.55 ms
64 bytes from server-18-239-18-128.ams58.r.cloudfront.net (18.239.18.128): icmp_seq=3
ttl=251 time=4.50 ms

--- skbooks.co.kr ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2002ms
rtt min/avg/max/mdev = 4.501/4.598/4.742/0.103 ms