The cost of sending 'nil' over the network

What is the cost in bytes to send a ‘nil’ value over the network? Is it less than a boolean? I’m running some tests to see which data types require the least amount of bytes to send over the network, but I’m unsure about nil values, specifically in comparing sending ‘nil’ values vs. boolean values that are false.

My understanding is that each argument should contain some number of bytes to specify type followed by the required data. It is conceivable that a boolean is type: bool; value: true/false and a nil value is just type: nil.