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Re: Gearbox reality check




Rich,

A minor correction to one of your statements.  In spite of the proposal to use a 66 aligned data stream in the WAN compatible PHY,
the SPE remains byte aligned.  There has to be some sort of, as yet undefined, "gear box" to stuff, re-time, and re-align the 66 bit
data stream into the byte aligned transmission signaling stream payload.

Thank You,
Roy Bynum
----- Original Message -----
From: "Rich Taborek" <rtaborek@xxxxxxxxxxxxx>
To: "HSSG" <stds-802-3-hssg@xxxxxxxx>
Sent: Monday, June 19, 2000 3:38 PM
Subject: Re: Gearbox reality check


>
> Seto,
>
> The WAN PHY layer diagram in
> http://grouper.ieee.org/groups/802/3/ae/public/may00/bottorff_1_0500.pdf, slide
> 4, shows the WIS sandwished between the 64B/66B PCS and SUPI.
>
> Integration is always an implementation issue. I'm not making any support
> statements regarding either SUPI or the WAN PHY, you know where I stand on this
> issue. I'm simply stating for the purposes of this discussion thread that the
> gearbox is implementation specific to the PMA service interface. For the
> proposed WDM WAN PHY, the PMA service interface is 4-bits wide and the gearbox
> is 66:4. Please also note that SUPI stripes 16-bit words on each line, so
> perhaps the gearbox is more appropriately defined as 66:16:4. Note also that the
> SONET overhead defined in the WIS is byte (octet) aligned, whereas the SONET SPE
> is 66-bit aligned, implying that the gearbox is likely to be integrated into the
> WIS.
>
> Best Regards,
> Rich
>
> --
>
> "Seto, Koichiro" wrote:
> >
> > [Date: 06/19/2000  From Seto]
> >
> > Rich,
> >
> > I don't understand.
> > When WAN PHY uses 4-lane WDM PMA (SUPI), it still uses SONET framer (WIS)
> > before facing to the 4-lane interface.  Are you saying that WIS would be
> > inevitably integrated with 64B66B PCS?
> >
> > Seto
> >
> > >
> > > Ooops!
> > >
> > > I should have written 66:4 instead of 66:6 to cover the case of 66-bit frames
> > > going across a 4-lane WDM PMA interface for the WAN PHY. Sorry 'bout that!
> > >
> > > Best Regards,
> > > Rich
> > >
> > > --
> > >
> > > Rich Taborek wrote:
> > > >
> > > > Roy,
> > > >
> > > > The purpose of the "gearbox" you mention is simple and straightforward.
> > > > However, it should be noted that the gearbox is implementation specific
> > > > to the PMA service interface. The 66:16 gearbox converts 66-bit sub-frames
> > > > and slices them up into 16-bit chunks for transport over 16-bit interfaces
> > > > such as the XBI proposed as a PMA service interface:
> > > > http://grouper.ieee.org/groups/802/3/ae/public/may00/robinson_1_0500.pdf
> > > >
> > > > Other 10 GbE PHY implementations may utilize a 66:6 gearbox or no gearbox
> > > > at all in the case that the PMA service interface is a 1-bit serial
> > > > interface.
>
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