Tutorials/Tips

So that is how SSH got assigned port 22

Secure SHell (SSH) is the most popular remote management application that’s both available to enterprise and end users. By default, the daemon listens on port 22. You can change it to listen on an unprivileged port, but port 22 is the default. But did you know how that came to be?

Tatu Ylonen, the guy who wrote the protocol, told the story in a very short blog post. The story, er.. blog post begins…

I wrote the initial version of SSH in Spring 1995. It was a time when telnet and FTP were widely used.

Anyway, I designed SSH to replace both telnet (port 23) and ftp (port 21). Port 22 was free. It was conveniently between the ports for telnet and ftp. I figured having that port number might be one of those small things that would give some aura of credibility. But how could I get that port number? I had never allocated one, but I knew somebody who had allocated a port.

The basic process for port allocation was fairly simple at that time. Internet was smaller and we were in very early stages of the Internet boom. Port numbers were allocated by IANA (Internet Assigned Numbers Authority). At the time, that meant an esteemed Internet pioneer called Jon Postel and Joyce K. Reynolds. Among other things, Jon had been the editor of such minor protocol standards as IP (RFC 791), ICMP (RFC 792), and TCP (RFC 793). Some of you may have heard of them.

To me Jon felt outright scary, having authored all the main Internet RFCs!

Anyway, just before announcing ssh-1.0 in July 1995, I sent this e-mail to IANA: Continue reading

openSSH logo

LinuxBSDos needs your donation to continue!

I hope this article has saved you valuable time and effort to fix a problem that would have taken more time than is necessary. That makes me happy, and why I love doing this. But because more people than ever are reading articles like this with an adblocker, ad revenues have fallen to a level that's not enough to cover my operating costs. That's why I want to ask you a favor: To make a one-time or recurring donation to support this site and keep it going. It's a small favor, but every one counts. And you can make your donation using Patreon or directly via Paypal. Thank you for whatever donation you're able to make.

Donate via Patreon. Donate via Paypal.

Aside from donation, you may also signup to receive an email once I publish new content. Your email will not be shared or traded to anyone. And you can unsubscribe at any time.

Please share:
Tags:

We Recommend These Vendors and Free Offers

Launch an SSD VPS in Europe, USA, Asia & Australia on Vultr's KVM-based Cloud platform starting at $5:00/month (15 GB SSD, 768 MB of RAM).

Deploy an SSD Cloud server in 55 seconds on DigitalOcean. Built for developers and starting at $5:00/month (20 GB SSD, 512 MB of RAM).

Want to become an expert ethical hacker and penetration tester? Request your free video training course of Online Penetration Testing and Ethical Hacking

Whether you're new to Linux or are a Linux guru, you can learn a lot more about the Linux kernel by requesting your free ebook of Linux Kernel In A Nutshell.


Leave a Comment

Your email address will not be published. Required fields are marked *

*