[8023-10GEPON] [FEC] Notes to 12/2/07 Telecon and Next Steps
Attendees:
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Frank Effenberger
Brian Holden
Eric Lynskey
Glen Kramer
Frank Chang
Feng Dongning
Shoichiro Seno
Jeff Mandin
Notes:
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Jeff presented his slides on upstream burst initialization (http://www.ieee802.org/3/10GEPON_study/email/msg00426.html).
Discussion continued for 90 minutes or so (til 0230 my time)... There was not time for a proper wrap-up - so please see "next steps" section below.
As in the last call, there was some discussion on topics such as whether it's better for the spec to have one FSM vs. having more than one FSM with communication between etc. but we agreed to focus on the issues with real technical impact.
Among the topics discussed:
1) Whether the burst initialization sequence should align the 66b encoder to the start of the first frame of the burst (ie. just as it aligns the FEC codeword to the first 66b block of the burst). Or whether alternatively the alignment should stay as it was when the laser was off. It has been suggested that this has ramifications for MPCP.
1a) Relatedly: whether the Data Detector (and burst initialization sequence more generally) should look at the content of the XGMII words - or instead determine the start and end of the burst implicitly from the synchronization headers of 66b blocks with scrambled payloads.
2) Subrating vs. Superrating. Pending the decision of the appointed adhoc group, the FEC group prefers for now to orient its scheme for the subrating option. Subrating seemed to be the preference of all the FEC participants who expressed an opinion.
3) How to perform IDLE insertion/deletion in the subrating case. There is agreement that the IDLE deletion function belongs above the 66b encoder. Aside from that there are several broadly different ideas about what should be done (eg. having the RS send CRS to the MAC and somehow mark the southbound inserted IDLEs). Glen suggested expanding the scope of the adhoc to deal with IDLE insertion at the MPCP layer.
Summary + Next Steps
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There has been agreement for a while on the high-level flow for upstream initialization. The primary architectural difference between the 2 schemes on the table is whether to identify, frame, and align the burst on the basis of 32-bit XGMII words or on the basis of 66b blocks (as detailed in item 1 above). If this issue is settled soon, we should be able to work out the other issues and submit a consensus baseline proposal on the upstream for Orlando.
The following is my suggestion of how to proceed:
* Let's continue the focus on the upstream. If there is time before Orlando after completing a baseline proposal then we should move to the downstream.
* With respect to the alignment issue: I will prepare a summary the points raised on both sides, and also address the suggestion that there could be a difficulty in using the existing 66b encoder FSM to align at the start of burst. I'll distribute this by the end of Monday (hopefully). Anyone else is of course welcome to present their views on this topic.
* In parallel, I suggest that we prepare presentations to elaborate on the ideas for IDLE insertion/deletion that were mentioned this week. Please let me know if you interested in putting something together on this. I'd like do this particularly if our work is going to be described to 802.3 in Orlando.
Next Telecon
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The next telecon is current scheduled for Tues/Wed. Feb 20/21 at 1500 PST/ 2300 GMT/ 0800 JST. Bridge details are the same as last time.
BRs,
- Jeff