[ale] Calculating bandwidth for serial terminals

[Alan Bowman]

 Chris,
 Thanks for the input. I've got some idea now of how things work.

>
>#1 Standard speed wouuld be 9600 bits per second which equals 1200 bytes
>per second.  That would be for each terminal.
>
>#3 WCS you have 32 serial terminals.  Then you would expect to be using
>up 37kbps if this was at full stream.  I doubt you are up to full
>stream.
   Using the example above, I calculate that between the two Digi
Portservers I'm using 92.4kbps for the terminals and printers. All the
terminals are running at either 19200 or 38400 baud. All the printer
ports are at 9600 baud - they are mostly laser printers.



>You know the above.  What you need to do is sniff the network and see
>how much data is going between the 2 sites.
 This is going to hard to do, since I have no access to any of the
network devices, and I'm not sure if the Digi keeps that kind of
information. I might try to see if their network person will give me
some information other than "300k".



>You see Mulit-Tech Mux is much different than a Digi Terminal Server.
>I would say that it is possible to get much better speed over the Mux
>connection due to many facters.
  This has been my experience also. But, when someone wants to spend
tens of thousands of dollars, the sales folks aren't going to say no.


>#1 TCP/IP overhead:  Considering that each packet on a network has
>multiple headers and ends up have one byte for data.  That is the key
>pressed.  2 packets since that character is being echoed by the remote
>system.  This is extreme overhead.
  I guess this is what I need to figure out next - what overhead does
TCP/IP and the software add to the pipe.


>[Etherenet Header][IP Header][TCP Header]A
>
>Notice all the crap before the A.  This is the overhead that you are
>experiencing.  I alos assume that you are using Dig's "Real TTY' on the
>SCO box to fake true serial ports.
  That looks like a lot of overhead. And yes, we're using the Digi
Realport software. It does the job, and usually pretty well. We have
offices much larger than this one using the same hardware/software
setup, and they are quite happy with the speed.


>All I can say is as a result of this setup you've got much data going
>between the 2 sites.  I could be wrong but this is my opinion and I
>think others may have better ideas on how to fix.
  Their network person has mentioned moving the office to a "faster"
line, so there may be some light ahead. But either way, I wanted some
facts and figures to work with.


>The MUX truly is a fantastic piece of gear.  Sure it may be "old" and
>not so sexy as technology is concerned but neither are Wyse 50's.
  I've always been very impressed with the reliability and overall
performance of the Multitech muxes we sell. You're right, it's not the
newest fastest bestest, but they run forever, and are built like tanks.
For offices that don't have access to broadband, they are the best
solution to setup multiple terminals and printers at remote offices.
As for Wyse CRTs..  I've got a Wyse55 on my desk at work, and I use it
more than I ever use my PC. If it wasn't for the CRM package and the
fact we have to use Outlook and Office, I could do my job from my Wyse.

Thanks for the input. Very valuable.

...alan


 --
And on the seventh day, He exited from append mode
(Linux fortune)


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