Heh. Anyone remember the ping of death[0]? A lot (most?) of computers on the early internet didn't properly handle large packets, _especially_ from ICMP pings. Once upon a time, you could send a single ping w/ a packet size of 65536 and crash the remote.
He stores data in ICMP ping packets, but also Tetris board states, among others. If you are not familiar with Tom7, let this be an introduction to a heavyweight whimsical internet nerd
> There was a desperate search for better memory. We seriously considered. at one stage. renting a television microwave link from Boston to Buffalo and back so that one could store something like 3,000 bits in the 3 milliseconds of round-trip transit time.
Though I'm not sure why they wouldn't have just used a delay line for that task: that form of memory was already in use in computers, as discussed by Forrester himself from 11:15 https://www.youtube.com/watch?v=JZLpbhsE72I&t=675s .
[1] https://lcamtuf.substack.com/p/how-do-wood-finishes-hold-up
Srsly... the ram inside a core router is some of the most precious resources around... this is an ooold idea.. people were doing at least as far back as the 2000s.. i showed them how our router (Avici TSR) worked and said "please don't use the super fancy fabric temporary store for this."
This kills the router designer.
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.
Imagine mailing somebody a letter with data; once they receive the letter they send it back. The information is stored within the postal system.