The Interpolation Buffer is by default 3 server frames long (Interpolation between 4 Snapshots). So if the latency is 50ms and one server frame is 50ms, the Interpolation Buffer would be 200ms long.

In order to make interpolation really smooth it's required to build a smooth interpolation function (e.g. differentiable up to infinity — for all derivatives). It could be achieved using Lagrange's ...