https://help.maximumasp.com/KB/a445/connectivity-testing-with-ping-telnet-tracert-and-pathping-.aspx
What are Traceroute, Ping, Telnet and Nslookup commands? - Hosting https://www.namecheap.com/support/knowledgebase/article.aspx/9667/2194/what-are-traceroute-ping-telnet-and-nslookup-commands