Imagine a continuously-moving loop that stores bits. When you want a certain bit you just wait for it to loop back to the position you want.

Good, but how does a ping hold data? AFAIK each ping is a single round trip and not a continuous loop. And where in the packet is the data stored?

	▲	robjs 26 minutes ago \| parent \| next [-]
		ICMP packets pretty much always carry some data (even though it's not _strictly_ required). This data is what is padded when the user asks for a ping with a specific packet size (e.g., when debugging MTU issues). In some applications, using an ICMP payload and getting a quote of the IP header + 8-bytes of the original packet back in ICMP error messages is part of the application. For example, traceroute utilises the fact that it gets part of the payload back in a ICMP TTL exceeded message to identify _which_ traceroute request was being responded to.
	▲	36 minutes ago \| parent \| prev \| next [-]
		[deleted]
	▲	lesuorac 34 minutes ago \| parent \| prev [-]
		In everybody else's router as it travels back and forth. Imagine mailing somebody a letter with data; once they receive the letter they send it back. The information is stored within the postal system.