Hardware Identity of U-Verse Install

When they installed my U-Verse, the apartment complex had prewired it with Fiber Optic to a Service Panel, and Cat5e or Cat6 copper to locations within the unit. When ATT came in, they installed a UPS and a "Box" which the Fiber Optic is connected to.  there are four RJ-45 ports on this box, but only one is used and is spliced into for one Cat cable to provide network connections to my computers, and the other to where they placed a "Modem" box but It also provides the wireless wifi and has network connections on it. (I think it's a ARRIS brand).

They only used two wires from the RJ45 connection into the box inside of the service panel. I'm having issues with the speed and reliability of the network connection. It seems to drop out frequently and I can not even stream ONE Roku device without pausing for downloads.  I have the "24MB" connection speed.  My 5MB connection in SC with TWC was faster and more reliable, so I suspect there's an issue with the ATT configuration.

What is the 'box' inside of the service panel?  Can I test if my problem is the CAT cables in the apartment by disconnecting the RJ45 and connecting an ethernet cable from that box to the PC?