[802.3ae_Serial] Re: SJTP: WIS Pointer Processor
Tom, Tim,
In today's conference call, I asked about the different
BERTs that are available. There were 4 people in attendance.
All of them showed a preference for the bit based variety.
The statement was made that box vendors probably used SONET
frame based BERTs while transceiver vendors probably used
bit based BERTs.
More unscientific survey results are probably needed before
we make any decision on this. :)
Ben
Tom Alexander wrote:
>
> I agree with Tim. Just about every SONET person I've talked to
> on this subject expressed surprise at the notion of trying to
> sync to an arbitrary pattern. The industry standard apparently
> is to include SONET framing within the BERT, such that the
> payload could be properly extracted and checked. However, when
> I presented the WIS jitter test pattern proposals in St. Louis,
> a strong message was received from various people to the effect
> that they wanted to program up a bit sequence into the BERT
> and sync on that.
>
> We should probably put this to bed first before continuing on
> the WIS jitter pattern work. If the conclusion is that the WAN
> and LAN PHYs will take different approaches (not just different
> patterns) to the test equipment, then there's no need to invent
> all these patterns for the WIS - just point at the ITU docs that
> Tim has thoughtfully provided, without modification.
>
> - Tom
>
> -----Original Message-----
> From: Tim Warland [mailto:twarland@nortelnetworks.com]
> Sent: Wednesday, June 13, 2001 8:46 AM
> To: Ben Brown
> Cc: stds-802-3-hssg-serialpmd@ieee.org
> Subject: Re: SJTP: WIS Pointer Processor
>
> Ben Brown wrote:
>
> <snip>
>
> > For the WAN pattern, this is not the case. Your proposal already
> > suggests we're using 29% of the total PRBS but we're complicating
> > the process by starting the PRBS at a defined location on every
> > other SONET frame.
> >
> > I'm being told by AMCC internal sources that BERTs exist which
> > are able to synchronize to the SONET frame then synchronize to
> > a PRBS within the payload area of that frame. If this is the
> > case, why can't we simply let the PRBS run from any known
> > starting location? It would simplify the generation of the
> > payload in regards to timing it to the SONET frame. It would
> > also no longer require ignoring a group of errors at the start
> > of every other frame.
>
> This is correct (again). There are SONET based BERT testers
> which remove the payload from the overhead, then perform
> synchronization and report BER. For these machines, and for
> the WIS receiver for that matter, a free running PRBS generator
> works well.
>
> The discussions we had within the WIS jitter ad hoc focused
> on BERT test equipments which were not SONET based. I refer
> to these as bit based BERTS. A bit based BERT has no concept
> of SONET frames. It examines each bit individually, so it must
> know what each bit is going to be. If the PRBS is allowed to float
> within the SONET frame, the bit based BERT can not be
> expected to know this relationship. It would report the expected pattern
>
> not matching the bit sequence with which it was programmed.
> This was my justification for "locking" the PRBS within the
> SPE - in which case every bit within the two frames can
> be predicted in advance.
>
> It is up to the SJTP ad hoc to define the test pattern and therefore
> the type of test equipment which would be required. Should we
> require the use of SONET based BERTs for 10GBASE-W, or
> require a bit based BERT for 10GBASE-R and 10GBASE-W?
> As Ben says pattern generation and checking is easier with the
> SONET BERT.
>
> --
> Tim Warland P.Eng.
> Hardware Design Engineer Broadband Products
> High Performance Optical Component Solutions
> Nortel Networks (613)765-6634
--
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Benjamin Brown
AMCC
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