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Re: lag with version 8.1.12

Bryan Stansell bryan@conserver.com
Mon, 7 Nov 2005 14:06:30 -0800 (PST)

lorne and i have been working offline about this and it looks like the
perle term server (CS9032) has a telnet option processing bug.  at
least, that's what i believe.  after looking at the debug output, it's
obvious that the "ECHO" and "SGA" options keep getting renegotiated,
which is causing the lag.  the term server is running 8.3.0G (basically
the latest), and perle has been notified (though they haven't confirmed
there is a bug or have an eta for a fix - since i don't have a support
contract).  but it has been sent to their engineering group, at least.

if anyone else runs into this, one way to work around the problem is to
set the 'protocol raw;' option for the consoles.  that will prevent
conserver from doing any telnet option negotiation (though you'll end up
with those coming out a text, being sent to clients and logged to
files...but that's just an annoyance).  i'm currently thinking about
putting some logic in conserver to determine when it's already "acked"
an option and to ignore future ones.  this is kind of specified in the
telnet rfc (854):

      b. If a party receives what appears to be a request to enter some
      mode it is already in, the request should not be acknowledged.
      This non-response is essential to prevent endless loops in the
      negotiation.  It is required that a response be sent to requests
      for a change of mode -- even if the mode is not changed.

it's kind of ambiguous (does this apply to "DO" requests only or "DO"
and "WILL"?).  i also think i'll be looking at a good open-source
reference implementation, just to see what others do.  anyway, a
non-response should be ok, i think.

and here's the summary of the option negotation, for those who are
curious.  it doesn't stop at the end...it keeps bouncing between ECHO
and SGA.

    Term Server       Conserver
    -----------       ---------
    WILL ECHO ->
                     <- DO ECHO
    WILL SGA  ->
                     <-  DO SGA
               <- WONT TERMTYPE
    WILL ECHO ->
                     <- DO ECHO
    WILL SGA  ->
                     <-  DO SGA
    WILL ECHO ->
                     <- DO ECHO
    WILL SGA  ->
                     <-  DO SGA
    WILL ECHO ->
                     <- DO ECHO
    WILL SGA  ->
                     <-  DO SGA