Unique ID per Stream, in one Channel.
one side will always start with 0, while the other start with u64::MAX / 2.
number increases for each created Stream.
Every Stream has a Prio and guaranteed Bandwidth.
Every send, the guarantees part is used first.
If there is still bandwidth left, it will be shared by all Streams with the
same priority. Prio 0 will be send first, then 1, β¦ till the last prio 7
is send. Prio must be < 8!