I am on a remote with a customer on Package Server synchronisation issues.
We have blocked http traffic at the IIS level to only allow requests from one of the 3 unconstrained Package Servers. We are currently updating the package (downloading) at a rate of 2 packages per minutes.
This may look like a good number if the packages were downloading something, but no. We are only downloading the package.xml from the server (served by GetPackageInfo.aspx) and then the snapshot.xml (from the url/unc path provided in the package.xml).
So why is it downloading at such a slow rate? First of all because we reduced the Retry Delay and MaxRetry Delay  to the lowest possible values: 1 and 1 (each one minutes). So the AeXNetComms dll doesn't block outgoing requests for up to an hour as per default (in effect this change is benefiting the download rate a lot).
Still, with these aggressive settings in place the PS Agent spends between 50~75% of its time doing...