Searching for the information on link failure detection by RSTP, I have found the following website http://standards.ieee.org/reading/ieee/interp/802.1D.html. In this document you write : "Link loss may be detected by RSTP either by expiry of the infoWhile timer at a Bridge Port following a period of cessation of reception of BPDUs from the Designated Bridge for a LAN/link or by detection of a change in the MAC Operational status of the Bridge Port's MAC (attached to the LAN/link) link to FALSE. (The MAC Operational parameter in specified in clause 6.4.2 of 802.1t)." I am specifically interested in the MAC Operational status. This parameter is equal to portEnabled value from 802.1w. A change of portEnabled from TRUE to FALSE means a loss of a link. I cannot understand however what triggers this change. This is very relevant for my simulation of link failures. Is this information coming from physical layer ? When bridge knows that it should change this value? Is it the same for copper and fibre?
The appropriate reference for the definition of the MAC_Operational status parameter is now clause 6.4.2 of IEEE Std 802.1D-2004. This clause states: "The value of this parameter is determined by the specific MAC procedures, as specified in 6.5." Clause 6.5 describes the parameter value determination for IEEE Std 802.3 (in 6.5.1), IEEE Std 802.5 (in 6.5.2), and for other media access control methods (further subclauses of 6.5). These procedures may, in principle, differ for different physical media, as determined by the 802 Working Group responsible for the development of that MAC. Such variation may be explicit at the level of the description in clause 6.5, or be a consequence of the way that physical media dependent procedures contribute to the physical media independent function defined by the relevant 802 MAC standard. Reference should be made first to clause 6.5, and then to the specific MAC standards as called out by clause 6.5. This response was approved by 802.1 at its March 2007 plenary meeting.
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