The ICMP header starts after the IPv4 header. All ICMP packets will have an 8-byte header and variable-sized data section.
Windows "ping.exe" adds, by default, 32 bytes of padding
The Linux "ping" utility adds, by default, 56 bytes of padding
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C:\Documents and Settings\wentao.yang>ping 121.59.0.1
Pinging 121.59.0.1 with 32 bytes of data:
Reply from 121.59.0.1: bytes=32 time=1ms TTL=247
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yang@test.nmlon:~$ ping 192.168.231.0
PING 192.168.231.0 (192.168.231.0) 56(84) bytes of data.
64 bytes from 192.168.231.0: icmp_seq=1 ttl=251 time=1.06 ms
Ref: http://en.wikipedia.org/wiki/Internet_Control_Message_Protocol
http://ss64.com/bash/ping.html
