We recently updated the "Troubleshooting PI Client Connection Problems" whitepaper located at the link below. It now contains AF and Buffering considerations
This paper discusses ways to troubleshoot problems with PI clients or interfaces connecting to or communicating with PI Data Archive. For simplicity, “client” refers to both interfaces and other client applications such as PI ProcessBook, PI DataLink, and APISNAP. PI Data Archive may be a stand-alone server or a high-availability collective of servers that act as a single PI Data Archive server. Connections to PI Data Archive collectives are implemented on top of the same protocols used for connections to individual PI Data Archive servers. For the most part, troubleshooting connection problems to collectives or collective members is the same as troubleshooting connections to individual PI Data Archive servers.
This discussion begins with a background overview of PI networking. Basic troubleshooting steps are given, followed by discussion of specific issues that may cause problems with PI connections.