by Darius Kazemi, May 22 2019

In 2019 I'm reading one RFC a day in chronological order starting from the very first one. More on this project here. There is a table of contents for all my RFC posts.

Time out

RFC-142 is titled “Time-out Mechanism in the Host-Host Protocol”. It's authored by Charley Kline and Johnny Wong of UCLA and dated May 3rd, 1971.

The technical content

The issue at hand here is related to an error case not specified in the Host-Host protocol. Namely: what happens when no messages are sent over the connection for a long time? In other words, what happens when the connection stalls for some reason? That's qualitatively different from an error message.

They suggest the following algorithm.

The problem here is that if you assume the connection is closed, then you reconnect on the same socket, and then you get a response from the server for some very old message you sent in the previous session, then that is a confusing situation. There's no way to truly know if this new response is related to the old session or the new session. The authors are merely bringing this confusing situation to light and asking people for ideas for solving it.


My suggested solution is: don't reconnect on the same (local) socket after you close a connection. This would prevent this weird race condition from happening in the first place.

Hopefully we will see the answer to this in a future RFC.

Further reading

This is the first RFC authored by Charley Kline, who was apparently the person who sent the first message over the ARPANET. Here is an All Things Considered interview with Kline about that message and ARPANET in general.

I have more information about Johnny Wong in my RFC-117 post.

How to follow this blog

You can subscribe to this blog's RSS feed or if you're on a federated ActivityPub social network like Mastodon or Pleroma you can search for the user “@365-rfcs@write.as” and follow it there.

About me

I'm Darius Kazemi. I'm an independent technologist and artist. I do a lot of work on the decentralized web with both ActivityPub and the Dat Project. You can support my work via my Patreon.