Precedence is the precedence of the connection being
established. Zero represents the lowest precedence.
Note that non-zero values of this parameter should be
subject to authentication and authorization checks, which
are not specified here. In general, the distinction
between precedence and priority is that precedence
specifies streams that are permitted to take previously
committed resources from another stream, while priority
identifies those PDUs that a stream is most willing to
have dropped when the stream exceeds its guaranteed
limits.