Why is vCenter sending so much data to Avamar?

I just happened to notice our vCenter and offsite Avamar server have been incredibly chatty today. For the most part, it's more data coming from vCenter to Avamar, but there's also a good amount coming back from Avamar to the onsite vCenter.

What kind of communications do vCenter and Avamar send to/from one another? What would cause hundreds of megabytes to be sent back and forth over the course of a day?