OSI Model

>>> "Cynthia M. Kovarik" <ckovarik@bellsouth.net> 04/06/98
09:53pm >>>
> If you can provide me with your translations for the OSI model, I
> would be more than happy to provide you with the "sum total"
> received and perhaps an analogy for senior management.  

          ------------------------

I can't recall specifically which layer does what (other than the
absolute bottom one (7th?) being the actual hardware interface), but
try this for an understandable analogy:

Stuff (documents, E-mails, etc.) flying about a computer network are
like letters going through the mail.  Any letter sent anywhere goes
through several steps:

1) sender writes the letter & puts it in an addressed envelope
2) post man (or UPS or FedEx or whomever) picks it up 
3) post office sorts it in the appropriate mail bag for it's destination
4) mail bag is placed on conveyance to get letter to where it's going
5) at destination, bag is taken from conveyance to correct post office
6) post office puts letter in correct bag for delivery 
7) post man delivers mail to final destination 
8) recipient opens & reads sender's letter.  

Putting a 300Mhz Pentium/64MB/24X CD ROM/starfleet duotronic
component compatible PC on the desktops means steps 1 & 8 take a
total of about .0003 picoseconds.  But if the post man in step 2 is a
procrastinating centenarian with lumbago who's letter bag only holds
4 envelopes at a time, the post office in step 3 is hampered by
custodian's local 347 sit down strike as well as a flood of cards for
Groundhog's day, the conveyance chosen in step 4 is the Pony
Express, and the recipient has 400 other E-mails to read before he
gets to your letter, then it takes a looong time for the message to
get through, much less for you to see a response.  

Point is, there's lots of stuff happening between person A clicking
the mouse button and server B actually getting the mouse click
event, much less responding to it.  Layers of addressing abstraction
have to be resolved by things like routers (each mail bag probably
has an address (a number or some such) saying "I go to Detroit or
Boston or Paducah" over and above the actual address on the
envelope.)  Lots of traffic on the network itself (the Groundhog's
day cards) can slow down an individual message as well as increase
the time it takes to get the server to respond (the 400 E-mails.) 
Outages at any point force packets to be re-routed (the custodian's
strike.)  Older & slower transmission technology (our ancient
postman) and/or insufficient bandwidth (his very small letter bag) gum
up the works too.  Bottlenecks at any of the intermediate points
slows the whole process down, regardless of how golliwog state of
the art the desktop is.

Makes sense to me anyway - I've found the more outre the analogy,
the better chance it has of sticking in people's minds (and livens up
dry IS topics to boot :))

Scott Cornell
Mercy Information Systems
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