What is bufferbloat? If your router sends too much data to your modem, your modem will “buffer” that data. The buffered data is now quite literally waiting in your modem until it can send it. Why do I care? This wait period can be remarkably substantial and sporadic. If you are affected by bufferbloat, you will have perceivable spikes in lag. Note: Even if you have an “all-in-one” modem/router you can still have bufferbloat.