The ability to remotely login to a machine that’s miles away from you is perhaps one of the internet’s most popular applications. It might not seem so, but being able to access a remote host without a hard wire connection has transformed many areas of IT particularly in support and development. Obviously you need an account on the host that you are trying to login to, but actually using the machine as if you are at the console is extremely useful in many situations.
Two of the most famous applications for remote login access when using a TCP/IP based network (e.g like the internet) are Telnet and Rlogin. The most famous and probably used by every IT support technician over the age of 25 is Telnet, installed as standard in almost every TCP/IP implementation. It seems relatively simple but this actually hides some great functionality not least the ability to Telnet from one operating system to another. It’s incredibly useful to be able to sit at a Microsoft Windows machine with multiple command interfaces open in separate windows to Unix and Linux machines at the same time.
Remember these terminal windows are actually like physically sitting at the remote host’s console. This is is completely different from just using a web session or using something like an Italian to stream RAI player abroad like this. Each individual character that you type is entered into the remote host, there’s no streaming, no relaying or filtering. Obviously there are some restrictions about running a terminal windows on a completely different systems. However Telnet does an option negotiation phase between the client and server to ensure that only services which are supported at both ends are available.
The other famous remote login application is called Rlogin which was developed from Berkeley Unix. This application was initially only available on Unix Systems however it has been ported to most other operating systems now and you can Rlogin between Windows and Linux. Both of these applications use the Client/Server configuration – the client is the system where the initial connection is established to the remote server which is the target.
Nowadays, the most popular of the two application – Telnet has become much more sophisticated. Over the years lots of functionality has been added to Telnet whereas Rlogin remains quite simple and unmodified. However it should be noted that although Rlogin lacks features, it is a simple and stable remote access application.
The author – John Herrington has worked in IT for over thirty years in a variety of roles from support to latterly Network manager at a large bank. He now works for himself and runs one of the largest paid VPN services on the West Coast of America. He obviously works remotely a lot of the time but will rarely use Telnet as it’s too insecure!