Introduction to Remote Login

Remote Login is a process in which user can login into remote site i.e. computer and use services that are available on the remote computer. With the help of remote login a user is able to understand result of transferring and result of processing from the remote computer to the local computer.

Figure – Remote login

It is implemented using Telnet.

Procedure of Remote Login :

1. When the user types something on local computer, then local operating system accepts character.
2. Local computer does not interpret the characters, it will send them to TELNET client.
3. TELNET client transforms these characters to a universal character set called Network Virtual Terminal (NVT) characters and it will pass them to the local TCP/IP protocol Stack.
4. Commands or text which is in the form of NVT, travel through Internet and it will arrive at the TCP/IP stack at remote computer.
5. Characters are then delivered to operating system and which later on passed to TELNET server.
6. Then TELNET server changes that characters to characters which can be understandable by remote computer.
7. Remote operating system receives character from a pseudo-terminal driver, which is a piece of software that pretends that characters are coming from a terminal.
8. Operating system then passes character to the appropriate application program.

Figure – Remote login procedure

NVT Character Set :

• With NVT Character set, TELNET client translates characters into NVT form and deliver to network.
• TELNET server translates data and commands from NVT form to the other form that will be understandable by remote computer.
• NVT uses 2 sets of characters, one for data and other for control. Size of both characters is 8-bit bytes.
• For data, NVT is an 8-bit character set in which 7 lowest bits are same as ASCII and highest order bit is 0.
• For control characters, NVT uses an 8-bit character set in which the highest bit is set to 1.

Figure – NVT Character Set