According to the VCAP6 design blue print section

Objective 2.2 – Map Service Dependencies 

under tool   " VMware Application Dependencies and Entity Relationship Diagrams MK2"

this is a blog written by Ward8124

it stated

"The component closest to the end user is considered the upstream entity and therefore all components support this entity are considered downstream as a result."

i am confused, i thought the end users supposed to be the consumer of all the infrastructure we are designing, the end product, so it should be consider as down stream but not up stream ??  can somebody explain this further, i am reading but not fully understanding this..

Also I have a question about differentiating a Constraint and a non-functional requirement, they are almost equal under some situation but not all time as i read and read different articles, .... could the below statement from my understanding be true ??

"When we have a contraint, it may not necessarily/automatically become a non-functional requirement, a contstraint can just be a constraint on its own but when we have a non-functional requirement, it is automatically assumed to be a constraint ??"

Thanks guys