Re: [802.3_EPOC] MMP implementation issues: Multiple FCUs and MMP, is it different?
Matt: First, this is a good example to illustrate the rate adaption problem with MMP.
I am trying to understand what you mean..., If all 3 FCUs are capable to 4Gbps, total capacities would be 12 Gbps. If this is what you mean, then the total bandwidth available is limited at OLT at 10Gbps.
Thanks,
Eugene
From: Matthew Schmitt [mailto:m.schmitt@xxxxxxxxxxxxx]
Sent: Tuesday, January 08, 2013 1:33 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,
While at any given unit time I agree that the total BW would be as you indicate, if we're talking about the capacity available to each of the FCUs I don't think we can or should assume that they will always total less than or equal to 10 Gbps.
For example, let's say that an MSO is able to free up ~400 Mbps, and that we're able to achieve efficiency on order of 10 bits/symbol (to make the math easy). That puts each FCU sharing a single OLT port at ~4 Gbps. If there are 3 FCUs sharing that OLT port, that's ~12 Gbps; and that doesn't include any ONUs that might also be sharing that same OLT port.
If I'm following what you and Ed are suggesting, this configuration would not be possible, and the total bandwidth available to each FCU cannot exceed 10 Gbps. That seems like a problematic restriction which works contrary to the idea of using stat muxing to get better performance out of a shared medium.
Or am I misunderstanding that you and Ed are suggesting?
Thanks!
Matt
From: <Dai>, "Eugene (CCI-Atlanta)" <Eugene.Dai@xxxxxxx<mailto:Eugene.Dai@xxxxxxx>>
Date: Tuesday, January 8, 2013 11:20 AM
To: Matthew Schmitt <m.schmitt@xxxxxxxxxxxxx<mailto:m.schmitt@xxxxxxxxxxxxx>>, "STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>" <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.
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. 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@01CDEDA5.C4AE81D0]
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@01CDEDA5.C4AE81D0]
Edward Boyd | Sr Technical Director
Broadcom Corporation | (O) 707-792-9008 | (M) 707-478-1146
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