OS X 10.11.5 slow communication with NAS WD EX 2100

I have extremely slow communication with my NAS (WD EX2100) used for back-ups and storage after upgrading my iMAC to OS X 10.11.5. The firmware was also updated on the NAS but it runs only slightly faster after the firmware update as it did before the firmware update. For example: the Time Machine backup of 87.31 GB was running at a speed of .13 GB per hour or completion in 657hrs. The router is a Netgear R6300 AC1750 and Cat 5e cables. Communication speed was not an issue before the 10.11.5 upgrade. Reading files on the NAS presents the same extremely slow speed issues.