Perpetual UDP shell ?

[Dallas Helquist]

On Saturday 07 June 2003 12:44, Jeremy C. Reed wrote:
> On 7 Jun 2003, Bryce C wrote:
> > That's exactly the problem. With packet loss and no error checking, that
> > last c may be garbled and thus ignored by rm/bash. There's a reason SSH,
> > telnet, http, etc are all on TCP and not UDP.

False.  UDP has CRC checking to verify packet integrity.  It just doesn't care 
whether a packet got there or not.  So, the "last c" will either show up or 
you type it again - it will NOT be a garbled character.

>
> Back in the mid to late 1980's, I wrote a bunch of xmodem and BBS software
> (in Turbo Pascal). I used simple checksums to verify the data before
> acknowledging successful receipt (or complaining to resend). It would be
> simple to add that to a UDP-based remote login tool.

Yes, it would be easy to add those features.   UDP just leaves error 
correction (bad checksum == drop packet), sequencing, flow control, etc. up 
to the application itself.  UDP is a very simple protocol compared to TCP.

>
> But I don't see any advantage over using TCP and a regular SSH (or
> SSL-telnet or kerberized telnet) even for some "extremely unreliable
> connections such as a high altitude weather balloon communicating over
> packet HAM radio." :)
>
>    Jeremy C. Reed
>    http://bsd.reedmedia.net/
-dallas
>
>