We have connected two offices through a Cisco Lan-to-Lan VPN over the Internet. Users in one office Telnet to the other office to log on to a Unix app. This infrastructure is mandatory and cannot easily be changed.
The problem is that the Telnet connections can get very slow on occasion.
In an attempt to speed up the connections, we upgraded the connecting office from an ADSL line (4096 kb down, 512 up, not guaranteed), to an SDSL line (2048 down, 1024 up, guaranteed).
This hasn't improved things very much though.
I have the feeling that, because the Unix app is terminal based, it initiates TCP connections for each character pressed (a delay is noticeable when typing text), and therefore ping times are much more important than total bandwidth capacity. Ping times, however, have not decreased significantly, due to the crypto overhead of the VPN connection and the Internet tunnel that has not changed.
1. Can someone confirm or deny this? Do terminal-based apps initiate TCP connections per character inputted?
2. How can I improve performance on these connections?