Operating the Network Service Header (NSH) with Next Protocol "None"

This document describes a network that supports Service Function Chaining (SFC) using the Network Service Header (NSH) with no payload data and carrying only metadata. This is achieved by defining a new NSH "Next Protocol" type value of "None". This document illustrates some of the functions that may be achieved or enhanced by this mechanism, but it does not provide an exhaustive list of use cases, nor is it intended to be definitive about the functions it describes. It is expected that other documents will describe specific use cases in more detail and will define the protocol mechanics for each use case.