Local Fault/Remote Fault
First, let me say that I participated in the definition of
Local Fault and Remote Fault as presented at the November
meeting so I think I understand what was intended. The problem
I'm having is finding all of the pieces of that definition
in the draft so that those who didn't attend or see some
of the slides that were presented can understand.
With that said, what I did was search through D2.0 looking
for Local Fault and LF to find all of the associated text.
I may have missed some. What I found was incomplete and/or
confusing.
Here are the concepts I think we need to communicate:
1. Any device, in either its transmit or receive paths, could
detect a fault condition. The fault may be that the data
being received is invalid or that some internal problem
is causing the problem. Some/many faults may go
undetected. If a device detects a fault condition (i.e.,
a locally detected fault) it should set its link status
to zero and not forward what is received, but should,
at its output, either:
a. generate a local fault pulse ordered set if it is
capable of doing so,
or
b. generate all zeros or all ones, making it probable that
the next device in the link will detect the problem and
(hopefully) generate a local fault pulse ordered set.
2. All devices not detecting fault conditions should forward
whatever is received. Local fault pulse ordered sets and
remote fault pulse ordered sets may be generated by other
devices and, when received, must be forwarded on. With the
exception of the RS layer, receiption of a Local fault
ordered set or a remote fault ordered set must have no
effect on the device receiving these pulse ordered sets.
3. The RS layer is where the Local Fault Pulse Ordered Set is
processed. The RS layer is the only place that a Remote
Fault Pulse Ordered Set can be generated. If an RS receives
a Local Fault Pulse Ordered Set it must stop sending packets
and begin sending alternating columns of Idles and Remote
Fault Pulse Ordered Sets. If an RS receives a Remote Fault
Pulse Ordered Set, it must stop sending packets and send
only Idles.
Devices detecting fault conditions set their link status to 0
and attempt to generate LF's (local fault ordered sets). In some
cases, multiple devices may be detecting faults and attempt to
send LF's.
Station management can obtain each device's status and localize
the problem.
What I found in the standard is in the following clauses:
45.2.1.2.3
45.2.2.1.7
45.2.3.1.7
45.2.4.2.3
45.2.5.2.3
46.2.5.1 (last paragraph)
46.2.6
Table 46-4
48.1.3.1
48.2.2
48.2.4.5 and 48.2.4.5.1
Figure 48-10
48.2.5.4 and 48.2.5.4.1 and 48.2.5.4.2
49.2.4.5
49.2.11.1.1 (definition of LFRAME_R)
Figure 49-14 --> top state
I don't think these "pieces" capture what we need. In fact, the
inconsist usage of terms is confusing. For example, what
does "detected a local fault signal on the inbound path" mean?
I think we need some standardized terms used through out.
And I think we need a basic description (better written than what
I did above) place somewhere in the intro and not in one of
the "component" pieces where it could be missed by others.
Before I start on what I think should be done, I'd like confirmation
that my description above is correct. I'll then start on my proposed
fixes.
Steve Finch