Re: [STDS-802-3-EPOC] [802.3_EPOC] MMP implementation issues: Multiple FCUs and MMP, is it different?
Salf: For you first question, in SMP case, the shaped BW of FCUA, B and C doesn’t have to be equal. The point is that we can put them in a single pipe with one rate and padding it to the targeted rare of 10Gbps, and then send to the XGMII. At PCS idles are removed, this is how 10G PON works. Rate adaption is straight forward in this case.
For your second question, no matter how small the variation between the MP in MMP, we end up shaping FCU A, B and C into pipes of different sizes which results a stream with “discontinuous” variable rate. We are facing the problem of padding variable rate stream into a fixed rate stream to XGMII and remove the LLID/MAC dependent ideals at PCS which does not have this information. Rate adaption mechanism of 10G PON does not for MMP.
To make things more complicated, each FCU could have CNUs with MMP, and then the shaped pipe for individual FCU could also be “discontinuous” variable rate stream. Rate adaption will be a nightmare.
However, everything will be simple for MMP in EPON + EOC architecture where there is rate decouple between PON and EOC. We are under strident restrictions in EPoC. On the other hand it is these restrictions give us the economic benefits of staying in EPON ecology zone. We have to accept the trade off to enjoy these benefits.
Thanks,
Eugene
From: Rahman, Saifur [mailto:Saifur_Rahman@xxxxxxxxxxxxxxxxx]
Sent: Tuesday, January 08, 2013 5:54 PM
To: Dai, Eugene (CCI-Atlanta); stds-802-3-epoc@xxxxxxxxxxxxxxxxx
Subject: RE: [802.3_EPOC] MMP implementation issues: Multiple FCUs and MMP, is it different?
Eugene
A couple of questions inline below in red…
Thanks
Saif
From: Dai, Eugene (CCI-Atlanta) [mailto:Eugene.Dai@xxxxxxx]
Sent: Tuesday, January 08, 2013 1:21 PM
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>
Subject: Re: [802.3_EPOC] MMP implementation issues: Multiple FCUs and MMP, is it different?
Ed & Matt: Let’s reinterpret what Ed outlined there:
With SMP, using the diagram below the total bandwidth equals:
Total BW = A+B+C +2ONU <= 10Gbps
Where A,B and C are shaped pipes of FCUA, FCU B and FCUC, and 2ONU is shipped bandwidth of the two ONUs in the diagram. Then a single constant bit stream is formed by adding all four shaped pipes. The traffic shaping in this case is no different from regular EPON bandwidth shaping. The Total BW <= 10Gbps. Also the total BW is constant. Rate adaption is happened at XGMII by idle insertion and deletion. Also note here we are adapting a constant data rate to a fixed data rate, which of cause, also constant.
When you say “A,B and C are shaped pipes of FCUA, FCU B and FCUC” , are you you assuming that the data BW (capacity) of FCU A = FCU B = FCU C? If so, I think this is too restrictive. I think in general you have to assume FCU A ≠ FCU B ≠ FCU C.
In MMP, we also need shaping 4 pipes as before, however, 3 pipes A, B ,and C are at different rate since they have different MMP. Then the combined bandwidth is a variable rate stream, i.e., if we measure the data stream at different time, we may get the rate of A, B or C.
If the MMP changes very slowly then would the combined BW still be variable? Is this case the same then as above if you assumed above that BW of FCU A ≠ FCU B ≠ FCU C?
Now at XGMII we are facing the problem of adapting a variable rate stream into a fixed rate stream. This is the problem we have been trying to explain during San Antonio and Hangzhou meetings.
Thanks,
Eugene
From: Matthew Schmitt [mailto:m.schmitt@xxxxxxxxxxxxx]
Sent: Tuesday, January 08, 2013 12:13 PM
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>
Subject: Re: [802.3_EPOC] MMP implementation issues: Multiple FCUs and MMP, is it different?
Ed,
Thanks much for putting this out there, as it helps illustrate where we may be making different assumptions.
For me, I was not assuming that the sum of A+B+C is less than or equal to 10 Gbps; on the contrary, I've been assuming that the total available bandwidth for the sum of the FCUs would likely be greater than 10 Gbps.
If you change that assumption, does that change your conclusion about the difference between multiple FCUs and MMP?
Thanks!
Matt
From: "Ed Boyd (Edward)" <ed.boyd@xxxxxxxxxxxx<mailto:ed.boyd@xxxxxxxxxxxx>>
Reply-To: "Ed (Edward) Boyd" <ed.boyd@xxxxxxxxxxxx<mailto:ed.boyd@xxxxxxxxxxxx>>
Date: Monday, January 7, 2013 5:32 PM
To: "STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>" <STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>>
Subject: [802.3_EPOC] MMP implementation issues: Multiple FCUs and MMP, is it different?
Jorge, Duane, and all,
I started a new thread since I wasn’t quite sure where to insert my reply. Let me start with the drawing with multiple FCUs question that you proposed.
[cid:image001.jpg@01CDEE51.F81156E0]
The assumption with multiple FCUs is that you are shaping 3 pipes (A, B, & C) inside the 10G EPON downstream. If you make that sum of those 3 less than the maximum rate, you can send them down the PON at the same with a single packet of jitter. The total bandwidth of the downstream is a constant since it is the sum of the 3 constants.
For Multiple sub-pipes: Total BW = A + B + C (Sum of 3 Constants)
In the case of MMP, you have a single pipe with a changing data rate based on the destination. The data rate from the OLT is not a constant or the sum of 3 pipes. It is going up and down based on the destination. A single shaping bucket is used but the debit for the reverse leaky bucket is different based on destination. The total bandwidth equation is an OR.
For MMP: Total BW = A | B | C. (The total bandwidth or maximum bandwidth is based on the traffic)
I hope that helps. I will send a separate email on the other issues related to the MAC layer solution.
Thanks,
Ed…
[cid:image002.jpg@01CDEE51.F81156E0]
Edward Boyd | Sr Technical Director
Broadcom Corporation | (O) 707-792-9008 | (M) 707-478-1146
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