Out of personal interest I am working my way through the IEEE standards 802.1D-2004 and 802.1Q-2014. I am using the earlier document to clarify meaning in the later document, since the addition of MSTP and SPB adds a lot of complexity to the standard. Would anyone like to clarify the exact meaning of 802.1D-2004, Section 17.6 final para: "If the designated priority vector is better than the port priority vector, the Port will be the Designated Port for the attached LAN and the port priority vector will be updated."? There seems to be a circularity with Para 1: "The port priority vector is the spanning tree priority vector held for the port when the reception of BPDUs and any pending update of information has been completed." If the reception and pending updates have been completed, how can the vector be later updated? Just to be clear, I am not asking for clarification about the operation of RSTP. I am asking for clarification of the meaning of the algorithm expressed in those paragraphs.