[Leica] Epsom P800 Update

[reid at mejac.palo-alto.ca.us (Brian Reid)]

In a technologically perfect world, everything would be connected with 
wires. They are fast and reliable.

WiFi is a convenient substitute for short wires, but it is not magic. If 
the WiFi sending and receiving unit have trouble talking to each other, 
they will slow down in the hopes of making it work.

WiFi repeaters/extenders are a really bad idea. Here's why.

Suppose you have devices A and B trying to talk to each other. A sends a 
message and B receives it. If, perchance, B is trying to send a message 
at the same time, then A's message does not get through and A has to try 
again. //??So does B, because its transmission was stepped on.

If A and B are far apart and both of them are trying to send something, 
it can be a factor of 10 to 20 slower than it ought to be, because the 
airwaves are busy and unreliable and both ends are gyrating to find a 
time slot in which it is safe to send.

Now add a single extender, M. A sends to M and M sends to B. The 
transmission pattern goes like this:

     A sends to M
     M sends to B

this occupies exactly twice as much air time as A sending directly to B, 
so now a single transmission uses two slots instead of one. So if B is 
trying to send, there are two opportunities for interference, one with 
the A-M transmission and the other with the M-B transmission.

When you print, the printer needs to respond that it has received that 
lump of data and is ready for the next one. So the conversation ought to 
go like this:

A to B: here is some data
B to A: thanK you. Send more.
A to B: here is some data.

If you have a repeater, the conversation goes like this:

A to M: here is some data for B
M to B: here is some data
B to M: thank you. Send more.
M to A: thank you. Send more
A to M: here is some data
M to B: here is some data

If there is another computer in the mix, that is neither A nor B, then 
it is also trying to find a time slot that is not being used. The use of 
a repeater doubles the number of time slots needed for a conversation.

I run wires as close as I can get them to where the computers and 
printers are, and then I use WiFi for the final connection.

Also, all WiFi is not created equal. If you have a WiFi router that is 
older than 3 years you should drive a heavy truck over it. Unless you 
are an expert you should use WiFi routers that employ the 802.11ac 
protocol. That's "ac", not"ad" or "af" or "n" or anything else. "ac". 
Don't buy "802.11ac Wave2"; it is not ready for general use.