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RE: new to console server / client (ASM, Yech!)

Zonker Harris Zonker.Harris@bigbandnet.com
Wed, 25 May 2005 08:55:29 -0700 (PDT)

  First off;  An ASM!! Oh My GOD! :-P
   (I declared the End Of Life on that during my days
    at Cisco, in the early 90's! Lots of warts on that
    unit! Save your pennies, and look for something
    better, ASAP! :-|

  OK, now, let me clarify;
  1) Which part of Canada are you from? ;-)

  2) PolyCentre is making the reverse-TCP connections
     to the ASM, and the ASM is making the physical
     serial connection with the RJ-11 jacks to your
     hosts, yes?

  3) You (or your users) then connect to the Poly Centre
     in order to communicate with the consoles (through
     the ASM), have I got that right so far?

  If so, then Conserver would essentially replace the
Poly Centre function, the reverse-TCP sessions would
be up all the time (and logging anything coming into
the serial ports on the ASM).

  The ASM should be replaced in this function, since
the unit has a SEVERE problem passing LOTS of data
at once. While capable (even in the mid-90's) of being
a 112-port terminal server, it's top port speed was 
38.4 Kbps, but the bigger issues were in Hardware 
Flow Control, and 'busy' ports...

  With the 6-wire interface used in the RJ-11, the
Cisco needed one lead for ground, and so the decision
was made to eliminate the ability for the ASM to tell
the attached device to hold it's data. (They determined
that they could process data coming into the ASM as
fast as a user could type, so they didn't need to be
able to say "Whoa!"...) They *did*, however, keep the
hardware handshake lead, so they could tell when an
attached modem was on-line.

  As for port speed, if you have 8 ports, configured 
for 9.6 Kbps, all getting data in at 'full-rate', your
ASM is maxed out...if a 9th port starts getting some
characters, everything slows down, buffers start to
fill, memory leaks, data is lost, and (eventually) the
unit will crash and reboot. If the ports are configured
for 19.2 Kbps, you only get 4 active sessions at once,
and if you run at 38.8, you only get two at a time.
Trust me. :-)

  I don't recall if the unit sent Serial BREAK. It was
early in Sun's life, and I wasn't paying attention to
that when I did the other testing. My guess is, that
it DOES send break, too. Bet to replace the ASM with
something Sun Safe. (See my BREAK testing pages for
more info. 

  You can use ACLs on Cisco gear (and there are similar
access controls on most Console Servers these days), so
that the Conserver host, and perhaps a few other trusted 
hosts, would be the only addresses allowed to connect
to the Console Server(s).

  The "portbase" argument is which TCP port Conserver 
will start using when it's counting the serial 'ports'
on each type of console server...

    In the Cisco world, the serial ports are usually
    found at TCP port 2000 + n, where 'n' is the number
    of the async line. (i.e., line #7 is at TCP 2007)

    In the Cyclades world, the calculation is 7000 + n...

  So, for Cisco units, the 'portbase' is typically
going to be 2000, and for Cyclades, 'portbase' would 
typically be 7000. (In many cases, you *CAN* change
that base port number on the Console Server as well,
in case you want to hide your ports some non-standard
number...if you change it on the console servers, you
would also need to change the portbase number in the
Conserver config as well.)

  From my main page (www.conserver.com/consoles/), look
in the Useful URLs section, and check out the Linux
Documentation Project links...Sections 4-6 are very
useful for configuring the BIOS, Boot Loader, and
GETTY configs for various machines, and may be of
help with your Debian PC. :-)