Re: Wisless Gearbox
Brad,
66-bit sub-frames arranged in a serial bit stream are sliced up into 16-bit
chunks, turned sideways and passed to the XBI and vice-versa. Yes, the
multiplexing logic is slightly more complex than this :-)
It is one heck of a lot simpler than a WIS Gearbox. Come to think of it, every
time I hear a "wis" kind of sound in a gearbox it means the bearings are shot.
The next sounds generally heard are either "clunk" or "grind" :-)
Best Regards,
Rich
--
"Booth, Bradley" wrote:
>
> Ben,
>
> Gold star!
>
> Now, can you explain how it works without the WIS? :-)
>
> Cheers,
> Brad
Brown, Ben 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
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Richard Taborek Sr. Phone: 408-845-6102
Chief Technology Officer Cell: 408-832-3957
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