doing this again.....
#nodes	#links for full mesh
1	0
2	1
3	3
4	6
5	10

i worked out this equation...
links = nodes*(nodes-1)/2

talking about basic combination permutation stuff, and how it relates to ^
order doesn't matter in combination
order matters in permutation

combination formula for M out of N items: N!/(M!(N-M)!)

now talking about ethernet and bus topology, resource contention, collisions, need for rules over line usage
alternate, token ring
point to point links
point to multipoint links

various paradigms
centralized computing - mainframes/terminals
cloud computing - 
master/slave configuration and polling/selecting protocols
timing diagrams
master		slave
| -> Poll A ->	|
| <-  Data  <-	| 
| ->  ACK   ->	|
| -> Poll B ->	|
| -> NACK   ->	|
each step has associated delay and possible data loss
need error detection and correction

master		slave
| ->Select A ->	|
| <-  ACK    <-	| 
| -> Data A  ->	|
| ->Select B ->	|
...