When 'ping' fails
In Networking, the 'performance objects' are links, usually end-to-end, consisting of many elements - like ethernet segments, switches, routers/firewalls, long-distance circuits and security scanner devices, laid on top of Telco/backbone services that provide dynamic and asymmetrical routes. The most frequently used measure is 'ping' time - ICMP “echo request” packets, often 64 bytes long. Firewalls, routers and underlying networks filter/block classes of traffic, implement traffic & flow rules and attempt "Quality of Service". There are many common rulesets in use: blocking 'ping' outright for 'security reasons'. Stops trivial network scanning. QoS settings for different traffic classes. VoIP/SIP gets high priority, FTP traffic is low, your guess on HTTP, DNS, time (NTP) and command line access - SSH, Telnet, ... traffic profiling on IP type (ICMP, UDP, TCP) and packet size (vs link MTU). traffic prioritisation based on source/destination....