[RE] Grand master identifier

[David V James <dvj@xxxxxxxxxxxx>]

All,

I was starting to update a group-contribution working paper,
when a couple of questions arose. For reference, these questions
are with respect to:
  http://www.ieee802.org/3/re_study/material/index.html
  Subclause 5.2.

We assume that the grand master is selected by picking one
of the clock-master capable stations. To do this, IDs need
to be distributed externally (between bridges and stations)
as well as internally (between bridge ports).

To avoid invention, we assume the existing STP identifier
format should be used (why be different?). The format, not
the actual values; an grand master could be different from
the STP root.

My original assumption was that the precedence value,
transmitted between stations, consists of:
  16 bits -- system
  48 bits -- MAC address
  16 bits -- port

Having started to write things in more detail, it seems
like the port information need only be used within a
bridge, and need never appear on Ethernet.

Pardon my asking, but the appropriate 802.1 documents are
not that easy for me to read. Am I correct in my recent
thoughts, that the port portion of this identifier is
only used within the bridge, and never appears on the outside?

DVJ