Hello Avid
When the term “flow” is used, it is referring to traffic that has the same source and destination address. So in both diagrams in the lesson, there are two flows: one from H1 to H3 and a second from H2 to H3.
Each router has a unique ID that is used for this algorithm. This means that for flow H1 to H2 for example, R1’s algorithm would send the flow via interface 1, R2s algorithm will send the flow via interface 2, R3’s algorithm will send it via interface 3 and so on. In other words, each router would calculate a randomly different exit interface. Conversely, the original algorithm would cause all routers to send the specific flow via the same interface, which can result in CEF polarization.
Now with the displayed examples containing two flows, the benefits of this are not immediately visible. Imagine you have 100 flows, or 1000 flows. The resulting algorithm will more appropriately distribute flows across multiple paths to more efficiently load balance traffic.
I hope this has been helpful!
Laz