RE: [802.3ae] Link Fault Signalling
Burt,
To continue on where Ben left off, the PMD and PMA don't have the capability
to generate LF, but they also don't have the capability to generate a data
stream that will achieve sync at the other end when they are not receiving a
good transmit data stream from their PCS. So, if the PMA or PMD detect a
fault on a path, they won't send out a valid stream on that path. The PCS
that receives what they send will detect a fault and it will send LF to the
RS. Any fault between RS sublayers should result in LF being sent to the RS
that is on the receiving end of the path with the fault.
Pat
-----Original Message-----
From: Ben Brown [mailto:bbrown@amcc.com]
Sent: Friday, December 07, 2001 8:30 AM
To: Burt Christian
Cc: HSSG (E-mail)
Subject: Re: [802.3ae] Link Fault Signalling
Burt,
You're getting closer.
Burt Christian wrote:
>
> > Thanks for the replies. My understanding now is as follows:
> >
> > 1. If a fault is detected on the receive path, at the PMD or
> > the PMA, Local Fault Ordered Sets (LFOS) will be transmitted
> > by the PCS to the RS. Consequently, the RS will send Remote
> > Fault Ordered Sets (RFOS) to the PCS.
This is correct.
> >
> > 2. If a fault is detected on the transmit path at any sublayer
> > including MAC, RS, PCS, PMA or PMD on the transmit path,
> > LFOS will be generated and transmitted by the PCS to the PMA.
> > (Although if a fault is detected on the transmit path at PCS,
> > PMA or PMD, it cannot be guaranteed that the LFOS would be
> > generated by the PCS and if they are, whether they will get
> > through the PMA or PMD.)
The standard does not dictate what happens with faults in the MAC
and RS. However, faults below the RS result in LFOS being generated
across the link where they are received by the link partner and sent
to the RS. Some devices in this path cannot generate LF (such as
the PMA and PMD) and must result in sending bad/no data/light.
Regards,
Ben Brown
> >
> > Thanks.
> >
> > Burt S, Christian.
> > Ceyba Inc.,
> > Systems Specialist
> > Tel : (613)599-5797
> > Fax : (613)599-1247
> > burt@ceyba.com www.ceyba.com
> >
> >
> > > -----Original Message-----
> > > From: Grow, Bob [mailto:bob.grow@intel.com]
> > > Sent: Wednesday, December 05, 2001 7:51 PM
> > > To: Burt Christian; HSSG (E-mail)
> > > Subject: RE: [802.3ae] Link Fault Signalling
> > >
> > >
> > > The RS only forces the transmit path to Remote Fault or Idle.
> > > It never
> > > generates Local Fault. The PCS only forces the data path to
> > > Local Fault
> > > (whether toward the RS or toward the fiber). At a RS receive
> > > (i.e., the
> > > link fault state machine), reception of Local Fault causes
> > > the transmit path
> > > RS to force Remote Fault; and reception of Remote Fault
> > > causes the transmit
> > > path RS to force Idle.
> > >
> > > --Bob Grow
> > >
> > > -----Original Message-----
> > > From: Burt Christian [mailto:burt@ceyba.com]
> > > Sent: Tuesday, December 04, 2001 7:07 PM
> > > To: HSSG (E-mail)
> > > Subject: [802.3ae] Link Fault Signalling
> > >
> > >
> > >
> > > Hi,
> > >
> > > I wanted to ensure that my understanding of the RS Link Fault
> > > Signalling mechanism is correct. I am trying to understand the
> > > mechanism rather than the details of the protocol. If someone
> > > can please confirm the following description to be correct, I
> > > would appreciate it.
> > >
> > > 1. If a fault on either the transmit path or the receive path
> > > of PMD or PMA is detected then regardless of the quality of
> > > the signal received by the PCS on the receive path, Local
> > > Fault Ordered Sets will be transmitted by the PCS to the RS.
> > >
> > > 2. Once the RS Link Fault Signalling State Machine (Figure 46-9)
> > > has entered the FAULT state with link_fault == Local Fault, RS
> > > will start transmiting Remote Fault Ordered Sets on the transmit
> > > path.
> > >
> > > One thing I would like to confirm is that the Local Fault Ordered
> > > Set will never be transmitted by the RS on the link where the link
> > > is defined as the communication channel between two RS peers. This
> > > is quite clear based on the very last section of 46.3.4.3 but I
> > > would like to ensure that I am not missing anything.
> > >
> > > Thank you.
> > >
> > > Burt S, Christian.
> > > Ceyba Inc.,
> > > Systems Specialist
> > > Tel : (613)599-5797
> > > Fax : (613)599-1247
> > > burt@ceyba.com www.ceyba.com
> > >
> >
--
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Benjamin Brown
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