Terminal Servers and Concentrators

[Robert Ford]

We are currently using multiport serial boards from Comtrol and Equinox
to serve terminals (mostly Televideo 950s) to 386-based UNIX machines
running ISC 2.2 UNIX.  The UNIX boxes are interconnected via ethernet,
running TCP/IP.

For the most part, we have been satisfied with the intelligent multiport
serial cards, especially with their low cost per port (about $50/port for 
16 ports).  However, we have experienced some board failures recently that
have undermined our confidence in their reliability.  Also, we are 
concerned about the number of slots they consume if we want to attach
64 terminals to one box (not to mention the extra cpu load).  

We are currently doing some research on ethernet terminal servers, multi-
plexers, and asynch terminal concentrators.  We are wide open in terms
of directions to move, but obviously want to find the solution that 
provides the best performance, reliability, and flexibility at the lowest
possible cost.  We have been somewhat dismayed to find the the cost of
an ethernet terminal server is 2-3 times as expensive per port as a 
multiport serial board solution.  The asych terminal concentrators seem
almost as expensive.

So, we could use some guidance.

1.  What are the pros and cons of each alternative?
2.  With each solution, what would bear the most load (cpu, network, etc.)?
3.  Which manufacturers are the best and most reliable?
4.  Any comment on whether we should go with stand-alone or
    chassis-based servers/concentrators?
5.  Does anyone know of a terminal server that will give us <$100/port?

Thanks for your help.

Bob Ford
-- 
Bob Ford                           (814) 234-8592x36
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