This article describes the SharePoint Multi Server communication within the SharePoint farm.
Physical architecture relates to capacity planning and sizing depends on the multiple factors. I took a very simple example and try to explain, Is SharePoint Farm follow the Network Layer Architecture or Not.
Physical Network Layer Architecture (Normal Flow)
How to know the actual Server Communication within the SharePoint Farm
Browse the Central Administration
Central Administration -> System Settings -> Manage Server in FARM
Microsoft SharePoint Foundation Web Application Service is responsible to communicate with Database Server.
IF Microsoft SharePoint Foundation Web Application Service activated on Web Server, Then Web Server by-pass the network layer architecture and directly communicate with Database Server.
As depict above farm information, Now SharePoint FARM Network layer architecture look like
How WSP deploy to Multi Server FARM
Microsoft SharePoint Foundation Web Application Service is responsible to move the WSP solution to another server, wherever Microsoft SharePoint Foundation Web Application Service activated. Service automatically deploy the solution in other servers.