protocols(5)

💖 protocols — bestie edition 💖

okay so this is the protocols manual page from section 5 (File Formats Manual), and it's literally just about a file. but like, an iconic file. let me tell you everything, no cap. 🦋

---

✨ NAME ✨

protocols — the protocols definition file. that's it, that's the vibe. 💅

---

🌸 DESCRIPTION 🌸

so this file is a plain ASCII file (yes bestie, plain ASCII, we love a low-maintenance queen), and what it does is describe all the various DARPA internet protocols that are available from the TCP/IP subsystem. 🫶

bestie, please actually consult this file instead of doing the goblin move of using the numbers in the ARPA include files, or — and I cannot stress this enough — even worse, just guessing them. 😭 the audacity. these numbers literally show up in the protocol field of any IP header, so guessing is not giving what you think it's giving.

🚨 IMPORTANT: keep this file untouched!! like, do not edit it. changes would result in incorrect IP packages. no seriously. protocol numbers and names are specified by the IANA (Internet Assigned Numbers Authority), so that's their job, not ours. periodt. 👑

each line is of the following format:

protocol number aliases ...

the fields are delimited by spaces or tabs. empty lines are ignored. and if a line contains a hash mark (#), then the hash mark and the part of the line following it are ignored — it's a comment, it said what it said. 💅

the field descriptions, let's go:

• protocol — the native name for the protocol. for example ip, tcp, or udp. slay.
• number — the official number for this protocol as it will appear within the IP header. the real one. the official one. ✨
• aliases — optional aliases for the protocol. cute little nicknames, if you will. 🎀

also lowkey fun fact: this file might be distributed over a network using a network-wide naming service like Yellow Pages/NIS or BIND/Hesiod. 🌈

---

🎀 FILES 🎀

• /etc/protocols — the protocols definition file itself. the main character. 👑

---

🌟 SEE ALSO 🌟

• getprotoent(3) — go read this one too, bestie 🫶
• http://www.iana.org/assignments/protocol-numbers — the official IANA list, iykyk 🌐

---

and that's the whole page, we ate and left no crumbs 🍓. this lovely little file lives on ✨ Linux man-pages 6.20 ✨, dated ✨ 2026-02-08 ✨. mwah 💋💖