RE: [802.3ae] Regarding Sequence ordered sets (Clause 48)
don't what your clause 48 concern is. I think the possible cases are all
described in clause 46.
Remote Fault sequence ordered set is only generated by the RS, and only in
response to detecting a Local Fault condition on the receive path.
Conceptually, the link fault state machine on the receive path switches a
transmit path mux from MAC frames to RS generated Remote Fault ordered
sets. This is done without sending a Terminate (sending a Terminate would
increase the undetected error rate). Action is similar for detection of a
Remote Fault condition, with the exception that a frame in transmission would be
truncated with Idle instead of sequence ordered sets.
Transmission of the Remote Fault sequence ordered sets
(or Idle) continues until the link fault condition is cleared. It is
theoretically possible when the condition is cleared to be in the middle of a
transmitted frame (either the same frame or a different one. At the remote
receive RS, the reception of either Idle or Remote Fault ordered sets will
terminate the initial starting frame fragment as an error frame. The
trailing frame fragment (no Start) will be ignored by the remote receiving
only looking at the data stream, at the receiving RS, a beginning frame fragment
and an trailing fragment can be separated by a string of columns starting with a
non-data column. The standard only describes generation of that string as
Local Fault sequence ordered sets, Remote Fault sequence ordered sets, or
Idle. The receiving RS though will behave the same if something else is
received within the string (e.g., a corrupted sequence ordered set, inserted
Therefore, a PCS encoder or decoder can will be hit
with changes from data to ordered sets, data to Idle, Idle to ordered sets,
ordered set to different ordered set, etc.
I have a question regarding Sequence ordered sets. Is it possible for sequence
ordered sets to appear in the middle of a data frame?
Clause 46.3.4 (lines 27-29) says that the RS can possibly truncate a MAC frame
being transmitted to generate Remote Fault Status over the transmit path. I
would like to know if this means that there will be a sequence ordered set
inserted in the middle of the MAC frame or will the MAC frame be terminated
(by sending a Terminate control character) before the Sequence ordered set is
inserted in the transmit path.