[j-nsp] Question about sampling rate - Juniper MX Series Edition 2

[Eric Van Tol]

Hi all,
I've been reading the much better information about Inline J-Flow in the Juniper MX Series O'Reilly book and there's a table in there that shows various sampling rates for MX sampling configurations (Page 770, Figure 8-5). It says a valid input-rate should match the formula: input-rate = 2n - 1. Why? Where is the exponent coming from? This isn't discussed anywhere in the actual docs, as far as I can tell, nor is there any explanation in the book.

Thanks,
evt