Re: [STDS-802-3-EPOC] Evaluation Criteria and Requirements Ad Hoc Minutes
ITU-T [T14/Q13] is specifying the accuracy of 1588 clocks in the G.8273 standard. I'm not sure if EPoC needs to have any timing accuracy requirements but if it does, it should reference the G.827X standards.
From: Marek Hajduczenia [mailto:marek.hajduczenia@xxxxxx]
Sent: Sunday, January 20, 2013 2:36 PM
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx
Subject: Re: [STDS-802-3-EPOC] Evaluation Criteria and Requirements Ad Hoc Minutes
Thank you Geoff,
I think you're referring to timing requirements, namely the maximum delay through PHY (or individual sublayers, e.g., PCS, RS, MPMC) that we specify for individual PHY types. I believe there is no doubt that we do specify such delay requirements in 802.3 (in fact, we have them in EPON as well, as far as I could trace for PCS, and MPMC defined separately).
What I do not think we have specified until now for any PHY (P2P or P2MP) is the tolerance for timing and synchronization transfer through the given PHY. Timing and synchronization in this case is a service supported by the PHY, but controlled by the upper layers. In simpler terms, what this would be asking us to specify the precision we guarantee for the transfer of IEEE 1588v2 packets across EPoC PHY. It is, I think, a novel type of requirement, though it is not only a PHY issue, but also affects MAC Client layers. Any value we could specify therefore (e.g. 150 ns of tolerance) would affect 802.3 and 802.1 layers together (as well as many things outside the scope of 802 in general), since it is a service layer requirement.
Regards
Marek Hajduczenia, PhD
ZTE Portugal
Technology Strategy Department
Edifício Amoreiras Plaza,
Rua Carlos Alberto da Mota Pinto, nr. 9 - 6 A,
1070-374 Lisbon, Portugal
Office: +351 213 700 090
Fax: + 351 213 813 349
Mobile: +351 961 121 851 (Portugal)
From: Geoff Thompson [mailto:thompson@xxxxxxxx]
Sent: Wednesday, 16 January, 2013 10:47 PM
To: Marek Hajduczenia
Cc: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>
Subject: Re: [STDS-802-3-EPOC] Evaluation Criteria and Requirements Ad Hoc Minutes
Marek-
Just a historical note...
Such timing specifications were common for PHYs when 802.3 was specifying PHYs for CSMA/CD systems.
Round trip delay was a crucial parameter in determining the diameter of a CSMA/CD network.
The numbers used for the initial work in that area can be found in Annex B of 802.3.
It was only when we went to full duplex systems that this type of material fell into disuse.
(CSMA/CD is, of course, just an access arbitration method for TDD)
Best regards,
Geoff
On 161//13 12:14 PM, Marek Hajduczenia wrote:
Duane,
First it would need to demonstrated that such a symmetry can be achieved with such a tight tolerance (I cannot even think or where to start to guarantee something like that), and only then draw conclusions on what the synchronization / frequency tolerance should be. Putting requirements into our project which are either system level requirements or have no evaluation as to their impact on the complexity / cost / performance of what we are trying to do, is just asking for trouble.
Let's not put the cart before the horse.
Marek
From: Duane Remein [mailto:Duane.Remein@xxxxxxxxxx]
Sent: Wednesday, 16 January, 2013 08:03 PM
To: Marek Hajduczenia; STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>
Cc: Duane Remein
Subject: RE: [STDS-802-3-EPOC] Evaluation Criteria and Requirements Ad Hoc Minutes
Marek,
I agree with you that this is a system level specification. But I think we need to develop PHY level specifications that ensure a system can meet this level of synchronization. I don't think this will be much beyond adding a requirement that EPoC US path and DS path within a PHY have a symmetrical delay within some bounds (such as ± 1 or 2 TQ ). While it is true that we didn't do this for EPON we may have gotten lucky. If it is relatively easy to accomplish I think such a requirement is in order.
Best Regards,
Duane
FutureWei Technologies Inc.
duane.remein@xxxxxxxxxx<mailto:duane.remein@xxxxxxxxxx>
Director, Access R&D
919 418 4741
Raleigh, NC
From: Marek Hajduczenia [mailto:marek.hajduczenia@xxxxxx]
Sent: Wednesday, January 16, 2013 12:15 PM
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>
Subject: Re: [STDS-802-3-EPOC] Evaluation Criteria and Requirements Ad Hoc Minutes
Steve,
I'd like to request that the minutes reflect concerns Leo and I brought forward in relation to the frequency and synchronization precision requirements. We believe these are not PHY specific requirements, but system level requirements. If such a requirement does find its way into PHY spec, there is no way to verify it separately, i.e., nobody measures what part of the system level precision budget is consumed in PHY alone.
I'd also like to have it recorded in the minutes (as mentioned on the call) that EPON does support mobile backhaul services with *no* requirements of this type thrown into the PHY specs.
Furthermore, I believe it was also mentioned that such a requirement would overly burden devices that are not expected to carry mobile backhaul services. However, in the PHY spec it is not possible to distinguish one from another (there is just a PHY), given that 802.3 does not provide product specs. Such system level requirements should be brought forward to the group that deals with a system level design.
Regards
Marek
From: Shellhammer, Steve [mailto:sshellha@xxxxxxxxxxxxxxxx]
Sent: Wednesday, 16 January, 2013 05:04 PM
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>
Subject: [STDS-802-3-EPOC] Evaluation Criteria and Requirements Ad Hoc Minutes
All,
Attached are the minutes for the Evaluation Criteria and Requirements Ad Hoc meeting this morning, and also the latest open issues list.
Steve
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