Re: [BP] Question regarding Channels

First, I'm not sure that there has been any conclusion that one particular BP or another cannot handle 10Gb serial traffic. Many other variables come into play first. I think that the most important are the Line code and real NEXT/FEXT performance.

Secondly, I think that an important data point for this TF is your statement that backward compat "would help al lot to bring P802.3ap based products much faster to market".

It seems to me that maximizing the impact of this PHY std does mean creating a solution which allows backfilling a backward-compatibility market, rather than addressing primarily greenfields development.

.../Mike

From: owner-stds-802-3-blade@listserv.ieee.org [mailto:owner-stds-802-3-blade@listserv.ieee.org] On Behalf Of Engels, Christian
Sent: Wednesday, October 06, 2004 2:05 AM
To: STDS-802-3-BLADE@listserv.ieee.org
Subject: Re: [BP] Question regarding Channels

Hi,

I am also a fence sitter here. Just a few comments from a market perspective. Current ATCA blade implementations use GbE on the fabric interface (according to PICMG 3.1). It would be a plus for P802.3ap based ATCA hub boards (switches) if they would (beside talking to P802.3ap compliant node boards) operate with existing node blade designs based on 1000BASE-BX. It would help al lot to bring P802.3ap based products much faster to market as not each node blade design would be required to be adopted to the new backplane standard.

So any technology decision you are making here should be done also with respect to backward compatibility to existing ATCA fabric technologies if possible. I understand that current ATCA backplanes may not be suitable for 10G and it would be acceptable to replace those by others with suitable material. ATCA connectors where initially not designed to cope with 10G. Obviously it would be desirable to keep this connector type for backward compliancy reasons. I appreciate any effort you are doing here to reuse current ATCA connectors for 10G.

Chris Engels, Strategic Marketing Manager

Motorola, Inc. Embedded Communications Computing Group

Tel: +49 (0)89 608 14-235 Fax: +49 (0)89 608 14-276

Lilienthal Str. 15 D-85579 Neubiberg/Muenchen

email: Christian.Engels@motorola.com http://www.forcecomputers.com

-----Original Message-----
From: Booth, Bradley [mailto:bradley.booth@INTEL.COM]
Sent: Mittwoch, 6. Oktober 2004 00:19
To: STDS-802-3-BLADE@LISTSERV.IEEE.ORG
Subject: Re: [BP] Question regarding Channels

John,

I've been sitting on the fence watching this, and I wonder if this is more about whether or not to support legacy vs. greenfield channels. If that is the case, the answer may be harder to achieve, but there may be some room for a compromise. Something that came to mind recently is that this could be similar to the existing Cat 6 and augmented Cat 6 discussion going on in 10GBASE-T. The interesting thing is that the model of a 55m channel of Cat 6 (legacy) is very similar to a 100m channel of augmented Cat 6 (greenfield). If there is a desire to support legacy backplanes (primarily ATCA which would support the Broad Market Potential requirement), but the reach on those backplanes is less than the 1m target objective, then is it possible that the legacy channel model (for its specified reach) could be equivalent to greenfield channel model at the 1m reach?

In other words, if the ATCA max. reach is 32", then could the channel models for that reach be equivalent to a greenfield channel that is achieving ~40"? So, if you specify the channel model based on the existing ATCA channel at 32", vendors should be able to use better materials to achieve the required 1m reach. This would permit support for legacy ATCA platforms while permitting better materials to be used for greater reaches.

Thoughts? Or should I just go back to sitting on the fence?

Thanks,

Brad

From: owner-stds-802-3-blade@listserv.ieee.org [mailto:owner-stds-802-3-blade@listserv.ieee.org] On Behalf Of DAmbrosia, John F
Sent: Tuesday, October 05, 2004 1:46 PM
To: STDS-802-3-BLADE@listserv.ieee.org
Subject: Re: [BP] Question regarding Channels

All,

The reflector appears to be very quiet. I would really like to have this discussion so we can try to move forward.

John

-----Original Message-----
From: owner-stds-802-3-blade@listserv.ieee.org [mailto:owner-stds-802-3-blade@listserv.ieee.org] On Behalf Of DAmbrosia, John F
Sent: Tuesday, October 05, 2004 10:39 AM
To: STDS-802-3-BLADE@listserv.ieee.org
Subject: [BP] Question regarding Channels

All,

Since time did not allow the conversation last week, I would like to talk further on the reflector to understand the opposition to the different channels that were proposed.

I will point to my test cases as a starting point, but the conversation really applies to all of the channels.

As I see it, we have the following types of impairments in the total system-

1.      Loss dominated
2.      Significant stub effects that cause deep nulls
3.      Ripple in the channel
4.      NEXT
5.      FEXT
6.      Return Loss

I believe most of the opposition arose from 1, 2, 3 and 6, but would like to have this conversation now.

The comments that I heard regarding my channels were the following -

·       The data is not freely available. - This is no longer true, as I indicated last week.
·       The data violates the informative channel model. I believe there were different cases where this happened.
o       Case 1 had minor ripple below the mask.
o       Cases 2 and 3 were margin cases that the Signaling Ad Hoc had requested.
o       Case 6 came from a 22" link with top layer backplane connections. This channel was justified for its potential appearance in systems where all cost was being minimized, so counterboring was not assumed.

o       Case 7 had a resonance ripple at approximately -55dB at 11 GHz. Once again this was a test case asked for by the Signal Ad Hoc to examine channel ripple. Otherwise up to 11 Ghz it is 5 to 15 dB above the informative mask

·       Return loss is too high. In my opinion, this is a contradictory statement. The mask that I proposed that fit my data was not as aggressive as Joel's channels (#1,2,3,6,7,8,14,17,18).    All of these models violated the proposed SDD11 mask in the lower frequency region, which I proposed.

·       The data hadn't been seen. This is a partially true statement. Tyco has been diligent in presenting the data as quickly as gathered and processed. The SDD21 channel data for Cases 2, 4,5,6, and 7 was posted to the Signaling Ad Hoc reflector for the Sept 9 meeting.

So I reviewed Joel's data that was proposed

Case #1 - 4_3_4 (4000-13) Total 11"

Case #2 - 7_3_7 (4000-13) Total 17"     has xtalk

Case #3 - 10_3_10 (4000-13) Total 23"

Case #6 - 4_10_4 (4000-13) Total 18"

Case #7 - 7_10_7 (4000-13) Total 24" has xtalk

Case #8 - 10_10_10 (4000-13) Total 30"

Case #14 - 3_3_15_7 (4000-13) Total 29"

Case #17 - 7_20_7 (4000-13) Total 34" has xtalk

Case #18 - 10_20_10 (4000-13) Total 40"

All of these test channels are well above the channel model. We will still need a test case that falls very closely on the informative channel model, which is where the Tyco channels 1 - 3 are falling (with included margin cases). From both IBM and LSI's analysis these channels were solvable. The StatEye analysis results were much more pessimistic (which is an on-going problem with StatEye that is being investigated) than the analysis of these companies and the crosstalk was not applied properly.

So to me it looks like overall loss isn't necessarily the big problem. Loss can be very advantageous, as was demonstrated at last week's meetings, as to how it can actually help reduce xtalk and return loss. Ripple and nulls on the other hand appear to be the bigger problem.

So I would like to open up discussion as to which Tyco channels people were most concerned about. Also, I do not know what to propose for a "weighting" scheme, so any suggestions on this would be of extreme use in helping us to reach consensus and move forward.

Cheers!

John D'Ambrosia

Manager, Semiconductor Relations

Global CC&CE

Tel 717.986.5692

Fax 717.592.2470

Cell 717.979.9679