icmp(4) on macOS
The text c5c1df2e0b54, as Mac OS X 10.4.11.x86, Mac OS X 10.4.11.ppc, Mac OS X 10.4.10.x86, Mac OS X 10.4.10.ppc, Mac OS X 10.4.9.x86, Mac OS X 10.4.9.ppc, Mac OS X 10.4.8.x86, Mac OS X 10.4.8.ppc, Mac OS X 10.4.7.ppc, Mac OS X 10.4.6.ppc, Mac OS X 10.4.5.ppc, Mac OS X 10.4.4.ppc, Mac OS X 10.4.3, Mac OS X 10.4.2, Mac OS X 10.4.1, Mac OS X 10.4, Mac OS X 10.3.9, Mac OS X 10.3.8, Mac OS X 10.3.7, Mac OS X 10.3.6, Mac OS X 10.3.5, Mac OS X 10.3.4, Mac OS X 10.3.3, Mac OS X 10.3.2, Mac OS X 10.3 shipped it.
Internet Control Message Protocol