Re: Gearbox reality check
Ben,
Your description is not close, it's right on! It's what I've been trying to say.
Thanks!
Best Regards,
Rich
--
"Brown, Ben [BAY:NHBED:DS48]" wrote:
>
> Rich, Roy,
>
> It could be the terminology that is confusing the issue. I don't
> think the results are any different.
>
> The SONET frame is byte aligned.
>
> The OH content is bytes.
>
> The SPE content is 66-bit words when being filled or emptied
> at the WIS. Since the SPE is not an integral number of 66
> bits, the last word in 1 SPE will often "spill over" into
> the next SPE.
>
> The SPE content is considered bytes when being passed through
> the SONET network. When the SONET network needs to "adjust"
> 1 SPE with respect to another SPE in order to account for
> clock jitter and tolerances, it does so on byte boundaries.
> This could potentially further separate a 66-bit word. The
> SONET network also uses byte boundaries to find the OH bytes
> within a frame.
>
> The result is that the WIS is required to parse the SPE based
> on byte boundaries as indicated by the pointer logic (to find
> the start of the SPE) but the data it extracts is organized as
> 66-bit words, i.e. it only uses the byte boundaries to find the
> start and end of the SPE and to separate the OH bytes, while
> the content of the SPE is considered a collection of concatenated
> 66-bit words.
>
> How close is this?
>
> Ben
>
> Rich Taborek wrote:
> >
> > Roy,
> >
> > This is the one of the tasks performed by the WIS. As I've explained, the SONET
> > OH is byte aligned and the data within the SPE is 66-bit aligned. Conversion at
> > each end is performed by the WIS.
> >
> > Best Regards,
> > Rich
> >
> > --
> >
> > Roy Bynum wrote:
> > >
> > > 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
> -----------------------------------------
> Benjamin Brown
> Router Products Division
> Nortel Networks
> 1 Bedford Farms,
> Kilton Road
> Bedford, NH 03110
> 603-629-3027 - Work
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> bebrown@xxxxxxxxxxxxxxxxxx
> -----------------------------------------
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