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Ping (networking utility)
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===Payload=== The payload of the packet is generally filled with [[ASCII]] characters, as the output of the [[tcpdump]] utility shows in the last 32 bytes of the following example (after the eight-byte ICMP header starting with {{Mono|0x0800}}): <syntaxhighlight lang="hexdump">16:24:47.966461 IP (tos 0x0, ttl 128, id 15103, offset 0, flags [none], proto: ICMP (1), length: 60) 192.168.146.22 > 192.168.144.5: ICMP echo request, id 1, seq 38, length 40 0x0000: 4500 003c 3aff 0000 8001 5c55 c0a8 9216 E..<:.....\U.... 0x0010: c0a8 9005 0800 4d35 0001 0026 6162 6364 ......M5...&abcd 0x0020: 6566 6768 696a 6b6c 6d6e 6f70 7172 7374 efghijklmnopqrst 0x0030: 7576 7761 6263 6465 6667 6869 uvwabcdefghi </syntaxhighlight> The payload may include a timestamp indicating the time of transmission and a sequence number, which are not found in this example. This allows ping to compute the round-trip time in a [[stateless server|stateless]] manner without needing to record the time of transmission of each packet. The payload may also include a ''magic packet'' for the [[Wake-on-LAN]] protocol, but the minimum payload, in that case, is longer than shown. The ''Echo Request'' typically does not receive any reply if the host was sleeping in hibernation state, but the host still wakes up from sleep state if its interface is configured to accept wakeup requests. If the host is already active and configured to allow replies to incoming ICMP ''Echo Request'' packets, the returned reply should include the same payload. This may be used to detect that the remote host was effectively woken up, by repeating a new request after some delay to allow the host to resume its network services. If the host was just sleeping in low power active state, a single request wakes up that host just enough to allow its ''Echo Reply'' service to reply instantly if that service was enabled. The host does not need to wake up all devices completely and may return to low-power mode after a short delay. Such configuration may be used to avoid a host to enter in hibernation state, with much longer wake-up delay, after some time passed in low power active mode.{{Citation needed|date=May 2016}} A packet including IP and ICMP headers must not be greater than the [[maximum transmission unit]] of the network, or risk being [[IP fragmentation|fragmented]].
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