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Re: [802.3BA] XLAUI / CAUI Ad Hoc

To those concerned about XLAUI/CAUI,


In general, we are supportive of the Piers Dawe presentation (dawe_03_0109.pdf) entitled “Compliance points for XLAUI/CAUI with connector” to be given next week in New Orleans, because we wish to see the standard include a chip-to-module specification for XLAUI/CAUI.  (I added my name as a supporter.)  The presentation currently considers a range of potential loss budget values to be considered for the nAUI chip-to-module normative specification, but in all cases the total loss including the loss in the module is limited to 10 dB. Under this overall 10-dB constraint, we make the following statements.


We believe the portion of the loss budget for the system host board should be as large as possible, since the overall solution includes the system host board and the module.  In consideration of cost, the system host board will have far greater incremental cost than the module when higher quality PCB material is used.  Cost sensitive applications using 40G interfaces will employ many such interfaces, which require fanning out signals to an array of 40G interfaces.  This fanning out also places a requirement for longer system host-board trace lengths or higher system host-board loss, which again prompts the need to use higher-cost lower-loss-rate PCB and/or higher-cost manufacturing methods.


We wish to see the system host-board loss be 8.2 dB.  However, we would continue to be supportive of the XLAUI/CAUI specification down to 7.5 dB for the system host-board loss.


In addition, since the Tx and Rx traces are segregated, FEXT is more important than NEXT. Thus, we would like to see the specification cover FEXT.  Frequency dependent masks should actually be specified for both FEXT and NEXT.








Jeffery J. Maki, Ph.D.

Principal Optical Engineer

Juniper Networks, Inc.

1194 North Mathilda Avenue

Sunnyvale, CA  94089-1206

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(Please leave messages by email.)

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IEEE 802.3 voter, OIF voter, & EA alternate voter

Member of OSA, LEOS, & IEEE




From: Ryan Latchman [mailto:Ryan.Latchman@xxxxxxxxxx]
Sent: Monday, January 05, 2009 1:05 PM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: [802.3BA] XLAUI / CAUI Ad Hoc


802.3ba Colleagues,


In order to include a chip to retimed module specification in 802.3ba, application level input is required on expected module trace lengths, host trace lengths, numbers of via, etc. for 40GbE and 100GbE. It would be extremely useful if this information can be provided in terms of loss.  


The XLAUI / CAUI team would appreciate any feedback in this area.  To start the discussion Chris Cole has already submitted the following input in Comment 295:


Max module trace length 3”
Max module vias: 2
Max host trace length 8” (or 6")
Max host vias: 2

Connector limits (similar to XFP connector):

Max connector insertion loss: 0.5dB at 5GHz
Max connector return loss: 21dB at 5GHz
Max crosstalk: 36dB at 5GHz


Best Regards,



From: Ryan Latchman
Sent: December 23, 2008 1:01 PM
To: 'STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx'
Subject: FW: [802.3BA] XLAUI / CAUI Ad Hoc


Hi Ali, Chris,


This is an important discussion which needs to get resolved quickly.


I would like to ensure that XLAUI / CAUI maintains its broad market applicability as a simple retimed interface.  I don’t think the current specification methodology prevents it from being leveraged to build retimed modules.  I’ve put together the attached material to show how retimed interfaces were specified in the past (namely XFI).  In XFI, you’ll notice that the Before Connector and After Connector specs are similar.  40/100GbE modules may have an analogous situation, depending on their size and electrical characteristics. 


If we need to change the XLAUI / CAUI specification, we need solid contributions on what needs to change. 


Happy Holidays,




From: Ali Ghiasi [mailto:aghiasi@xxxxxxxxxxxx]
Sent: December 22, 2008 5:59 PM
To: Chris Cole
Cc: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx; John DAmbrosia; Ryan Latchman
Subject: Re: [802.3BA] XLAUI / CAUI Ad Hoc



I just wanted to illustrate the difficulty members of 802.3ba would have in defining host-module interface for 100GBase-LR4/ER4 based on
publicly available information rather than in any way pointing to you for argument you did not make. 

You also say that specific implementation detail are inappropriate for the IEEE, but CR4/CR10, SR4/SR10 are based on very specific set of
assumptions.  The presentation I gave in Dallas, I made some very specific assumption on the module-host implementation which may be correct
or completely wrong, but we have to make some specific assumption please see page 5
Currently xAUI adhoc is defining transmitter mask instead of testing transmitter with compliance channel, in case the group decides to define
module-host compliance points then a 2nd transmitter mask must be defined at the output of module compliance board (see 2nd diagram on page 5).
In summary we have to replicate xAUI transmitter and receiver table for host and module.