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Interpretation #5
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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Last modified by jlm, at 5:33pm on Mon, 19 Mar 2007