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Hi
Jason: If
I follow your logic to completion, this would mean I have to cache *ALL* the IPS messages from *ALL* nodes and then when any event occurs
(like WTR), I would have to reprocess all those messages. This is because some
of the tests are based on packets from neighbors, and some are tests against
non-neighbors (state 28 for example). In
addition to the points I made below about sequence #’s, there can be problems
with startup. When a neighbor is instantiated, the sequence # is often 0
(structures are normally zero initialized). As such, the first neighbor message
will probably have a zero sequence too. Wouldn’t this cause that message to be
ignored? As
a side note…I defeated the sequence check, and the state machine seems to work
much more reliably – I actually end up with totally idle nodes rather than
stick WTR’s. Regards, Michael -----Original Message----- Hi Michael, The intent of line 36 is that if a TP frame is received
from a neighbor that meets the conditions of line 36 prior to the WTR expiring,
the relevant information in the TP frame will still be available for the
purposes of the check when WTR expires. At that point the transition will occur
into the IDLE state. The expiration of WTR is a trigger for doing state machine
processing just as when a new TP frame is received. -- Jason -----Original
Message----- I have been implementing the D2.2 IPS state
machine and run into what I believe is an issue with the new sequence # check.
If I interpret the check correctly, it looks like the first packet received
with a new sequence # is processed & then all future ones are suppressed
(until the sequence # changes again). It seems like this can cause a problem when
attempting to unwrap a link (on a wrapping ring), since a WTR node would
require state 36 to fire to get out of the WTR and the neighbor is the same as
the original. The problem is when the packet defined in state 36 arrives, but
the WTR timer has not expired. Once the packet has been processed, and the
timer later expires, it is not possible to get into state 36. Also, state 40 is the only state that
formally copies neighbor addresses. Since the whole state machine banks on the
neighbor MAC addresses being updated at the right time, this should be in the
state tables. It seems as though ALL
ClearXxxSideEdgeStatus() operations should remove a wrap. That way, reception
of IPS with STEER mode can switch the ring from wrapping to steered
immediately, and any current wrap conditions will get removed. Only the wrap
operation should be conditional on all nodes being able to wrap. Comments are welcome, Regards, Michael Allen |