> Could anybody tell me what is the minimum response time on an SLIP
> or PPP circuit in order to make TELNET works reliable?
Telnet should work fine over just about any reasonable IP connection.
You do want a RTT that is not very large. I personally start to notice
it when the RTT is > 200ms or so... it just does not keep up very well
with my typing.
You could probably run SLIP at 2400 baud and get an okay IP connection,
but telnet would seem very doggy and slow.