Most routers (by default) handle packets by a first in, first out (FIFO) method. This allows for a single application (such as a bandwidth test) to flood the router with packets, which makes it much less likely for other connections to have a fair share of the available bandwidth. This type of scenario will result in a high buffer bloat. The symptoms of this scenario are that latency-sensitive applications like VoIP, Skype, online gaming, etc., will be negatively impacted by not having a fair share of the available bandwidth.
The solution to this problem is to configure a quality of service (QoS) on your router. This is done by specifying what your max download and upload speeds are on the router, and then allocating priorities for bandwidth to applications, ports, protocols, or IP addresses. This method forces the router to prioritize packets based on these specified criteria rather than the FIFO method. The end result should be a lower buffer bloat if QoS is configured properly.