Re: Multiple TCP/IP servers on one host


Dave Crocker (dcrocker@TWG.COM)
31 Aug 88 08:35:00 PDT


You have a basic question to ask: Is the solution to your problem constrained
to use existing mechanisms or do you have freedom to implement additional
capabilities? If you must use only existing products, then you are unlikely
to find a solution.

In general, Keith Mitchell's set of alternative is reasonable, if you
can build your own mechanisms. (There are some interesting problems
involved with having the different milking machines know about each other
and each other's availability, but most of this is surmountable.)

Probably the minimum amount of effort -- even having a minute chance of
working without any development -- is to use the ability of the Domain
Name Service to list multiple addresses for a host. Here's how it goes:

1. For management purposes, list each milking machine by a unique name.
    Then, you can access specific ones, when you need to.

2. Choose a generic name, under which you list all of the milking machines'
    addresses.

3. When you need to do an access, use the generic name to do a DNS lookup
    and get the list of addresses.

4. Choose an address from the list. If you want to attemp load-leveling,
    throw a random number, to select the first address.

    (Sorry, but true, empirically-derived load-leveling does not work
    without all of the inter-milking machine communication mentioned above.)

5. Pray that the milking machine product sends a reasonable rejection when
    all of its lines are full.

6. When receiving such an error, try the next address.

The reason that you may be able to use this scheme without software development
is that there may be some telnet implementations out there that do step 6
already. Unfortunately, I doubt it.

Dave Crocker
The Wollongong Group



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