Placement of VNF in lower level Service Platform about son-hsp-pilot

[DarioValocchi]

More precisely, placement is an open issue more in general. We need:

• A SP placement plugin, or better an SSM, that deployes one VNF in the first PoP and a second VNF in the lower level SP.
• Maybe it's enough to have the a default placement plugin on the lower level SP (it will have just one PoP)

@tsoenen @mpeuster @hadik3r

[PhilipEardley]

I think that:

• the upper SP's placement function (*) decides that (let's assume the NS involves VNF-1 & VNF-2) it is not best placed to implement VNF-2 (either it can't do it, or it knows it's better to do it in the remote PoP)
• the lower SP's placement function decides where to place VNF-2
  (*) placement function or SSM - where the different functionality lies is a bit fuzzy to me
  In the Pilot, we can do whatever's easiest. For instance, the placement functions could have a built-in decision (default option), so effectively not have to decide each time.