Q: Mac Pro (2012) 10.9.5 Server 3.2.2 slower than Xserve network wise

We are an Apple Service Provider and handle the imaging of Macs for our University (using DeployStudio).  I recently migrated from two old Xserves running 10.6.8 Server to two Mac Pros running 10.9.5 with Server 3.2.2.  On both the old & new hardware, one NIC (en0 & Primary) was on a private network (diagnostics and imaging) and the other NIC (en1 & Secondary) was on a public facing network (access to file shares, etc.).  Both NICs are static IPs and fully populated with the appropriate numbers for their respective networks.  The private network is "managed" by our Telecom Department and does have a NAT connection to the public network.  Because this NAT is handled by our Telecom Department I have NO ability to see or check settings, nor do I know if ANYTHING was changed on or around the time I made the migration.  They are very protective and secretive about what they do to our network and when or why.  (e.g. looking into network settings is a DEAD END.)

Imaging from the Xserves would take less than 10 minutes.  Imaging from the Mac Pros takes as long as an HOUR.

I am a RHCT (now expired) and am familiar and comfortable in the Terminal.  My 'gut' tells me that some 'sysctl' value is "wrong" on the Mac Pros and is throttling the network connection.

Other than the newer hardware (more cores, double the RAM, etc), newer Mac OS, newer Mac Server version - all things are the same, even the same version of DeployStudio (1.6.12).

I didn't expect to see a major speed increase with the new servers, but I sure as heck didn't expect to see a six fold DECREASE in performance.

Anyone have any suggestions?

Happy to post any needed settings (sysctl or otherwise) details ...

Thanks in advance!