What does the "fl" field in /cdn-cgi/trace represent?

For example, GET https://cloudflare.com/cdn-cgi/trace returns

fl=202f30
h=cloudflare.com
ip=<the ip>
ts=<timestamp>
visit_scheme=https
uag=<user agent>
colo=<iata>
http=http/2
loc=<country code>
tls=TLSv1.3
sni=plaintext
warp=off

Most of the fields are self-explanatory, but what does 202f30 represent?

Thanks,
- John

2020-03-19 update: “FL accepts plain HTTP connections and does the main request logic, including our WAF” from Keepalives considered harmful

fl references our webserver and (I suspect) the value applies to a particular instance.

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Webservers are tied to a colo? This field appears to always differ per colo for the same hosted domain, but has some client affinity within a colo, subsequent requests have the same value for a while. What is the abbreviation fl short for?

Also, what does an instance refer to in this context? The hosted domain?

I receive sometimes different values in the same colo, so I don’t think they’re tied 1 to 1. Instance referenced an instance of the server, not of a domain. I’ll look to see if I can find any details describing but I associate fl with flare.

By “tied to a colo” I mean “exist within a single colo” (many to 1), i.e. I never see the same flare in different colos. At least I haven’t yet…

Would love to see some official documentation on how this value ties to the underlying infrastructure.

Just curious!

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Will share what I find. Chatted with the team, the fl designation is ultimately meaningless, was from an old team designation. The value identifies an instance.

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