Re: [8023-10GEPON] Presentation on FEC for 10G
Frank and all members of 802.3 10GEPON,
Your item 7 below sparked my interest. There's currently a project,
802.3ar, that would provide the appropriate MAC parameters to allow
exactly what you're looking for: slowing down the MAC to precisely the
rate you need to support whatever FEC overhead is eventually agreed
upon. However, as I understand it, 802.3ar is in grave danger of being
killed before it is allowed to go to working group ballot. I urge all
members of 10GEPON, specifically those members with voting rights in
802.3, to come up to speed with the intentions of 802.3ar and show up in
November to move this project along. Otherwise, you may not have a
choice regarding your options to item #7.
Regards,
Ben Brown
-----Original Message-----
From: Frank Effenberger [mailto:feffenberger@HUAWEI.COM]
Sent: Sunday, September 10, 2006 10:18 PM
To: STDS-802-3-10GEPON@listserv.ieee.org
Subject: Re: [8023-10GEPON] Presentation on FEC for 10G
All,
Here is a short summary of the call that on FEC.
The attendees were: Ryan Hirth, Frank Chang, Roger Berrel, Jeff Mandin,
and Frank Effenberger. Frank Chang kindly provided the conference call
number.
Frank E. prepared a short slideset to discuss some of the
byte/block/codeword alignment issues (see first attached preso).
These slides served as a sort of conversation starter...
The main topics of discussion were:
1. The topic of FEC can be broken into two parts: the FEC algorithm and
its effect on the optical performance, and the framing of FEC into the
10G Ethernet signal. The slides coming into the meeting focused on the
framing aspects. Frank Chang offered to prepare some slides on the
algorithm/performance topic. In fact, Frank C. has done this, which is
the second file attachment.
2. It seemed agreed that FEC needs to be at the lowest layer, and that
the 64b code blocks should fit evenly into the FEC code input (in other
words, the FEC input should be a multiple of 66bits or 65bits).
3. Time quanta - there was a variety of opinions on whether the time
quanta should stay the same as 1G EPON (16 ns), or if it should be
changed to fit the new speed better. No conclusions were drawn on this
issue on the call, although some people on the call needed to do more
work on the topic.
4. The line rate - there was a divergence of opinions on this issue,
too.
The original slideset presented the super-rate approach, where the MAC
rate stays at 10Gb/s, and the optics are speed-up to permit space for
the parity.
On deciding this super-rate, there were a variety of values, some based
on numerical theory and others on practical availability of serdes
parts.
Others on the call suggested that the PHY should stay at 10.3125 Gb/s,
and the MAC should be slowed down. It was also noted that increasing
the data rate will also increase receiver noise, so that must be
balanced against the bandwidth and architectural advantages. Once
again, a question to be discussed more.
5. 66b versus 65b coding - The first presentation presents the use of 66
bit versus 65 bit representation as a question. It seems that some
people like to stay with 66b code (for familiarity sake), and others see
the efficiency advantage of 65b representation.
6. Synchronization patterns - The first presentation illustrates a few
synchronization patterns that are intended for continuous synch. State
machine. It was noted that in the upstream, a special 'leader' pattern
would likely be needed to get FEC codeword delimitation quickly, so that
the state-machine could be kick-started. The length and operation of
these patterns was another issue that needs more work.
7. Layer-scope question - There was some disagreement on what is in or
out of scope of the current work, with some people claiming that it was
'easy'
to change parameters of the MAC, while others claiming the opposite.
This certainly will be an ongoing area of contention.
8. Agreed path forward - the involved parties agreed that it would be
good to re-draft the collected materials into a sort of presentation
which presented each design issue as a question, and avoided making a
position statement on any of the issues. This was seen as helping bring
the whole group up to speed on the topics. Frank C. and Ryan H. would
volunteer additional materials to the effort.
Thanks,
Frank Effenberger
-----Original Message-----
From: Glen Kramer [mailto:glen.kramer@teknovus.com]
Sent: Friday, September 08, 2006 1:08 PM
To: 'Frank Effenberger'; STDS-802-3-10GEPON@listserv.ieee.org
Subject: RE: [8023-10GEPON] Presentation on FEC for 10G
Frank,
Thank you for organizing the FEC discussions.
Few people have asked me for a summary of the FEC call. Would you
please, post to the reflector a short overview of the call: what was
discussed and any steps planned next.
Also, if you plan another conf call, please announce it on the
reflector, so that those who are interested, but missed the first call
could join this time.
I also want to remind everybody that the Ethernet Alliance has offered
10GEPON group a sponsorship in a form of hosting conference calls.
Please, let me know if you would like to have a conference call in
preparation for the September meeting.
Regards,
Glen