PuTTY sending extra characters at the beginning of TELNET connection initialisation

Question

When a TELNET session is initialised using PuTTY, I see that PuTTY is sending the following characters to the server at the beginning of the connection:

..... .....'.........

I was able to capture this using WireShark. The hex characters are as follows:

ff fb 1f ff fb 20 ff fb 18 ff fb 27 ff fd 01 ff fb 03 ff fd 03

Can you please help me understand why PuTTY sends these characters? I assumed it is something with the connection, but then, these characters are found in the DATA category of the WireShark capture.

Here is a video: https://www.youtube.com/watch?v=WGZru4KPmsM

Answer 1

Thanks to Some programmer dude and Elmi.

These extra chunk of characters are the negotiation sequences from PuTTY (client) to the server. Negotiations allow the client to have an enriched experience. A list of negotiation sequences in telnet protocol and their explanation is given here

If you are using PuTTY and do not need these sequences, go to Connection > Telnet and set the Telnet negotiation mode to Passive

Here is a link to Elmi's post