> I wrote the initial version of SSH (Secure Shell) 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.
Emphasis mine.
Cheers.
rsh was common on internal networks, but almost never used on the wider Internet. telnet was everywhere all across the net.
ssh was a revelation and it replaced telnet and authenticated/non-anonymous ftp primarily.
And also sometimes rsh, but less importantly.
The command line options were almost identical for an easy switch. ssh even respected the .rhosts file! Last time I checked, that functionality was still in place.
Both the rlogin-family of commands and the telnet/ftp-family were in use across the Internet, certainly in cases where Kerberos was used. I would think telnet was more common, certainly so outside the UNIX sphere of influence, but things like Kermit also existed.
They all got SSL-encapsulated versions in time, but Kerberos solved authentication for free, and for the simpler use cases ssh had already taken over by then. And in the longer run, simple almost always wins!
ssh solved the "pass credentials in cleartext over untrusted networks" problem. Consequently it replaced telnet and ftp. It also duplicated the functionality of rsh and rcp, so those protocols became irrelevant. But that was not the important goal.
> Kerberos solved authentication for free,
This made me laugh. Kerberos didn't do anything for free. :)
Even in Athena, Kerberos had reliability problems. In the wider world, it was very hard to find a well-managed Kerberos implementation. Things are different now!
