RE: Gearbox reality check
Now, can you explain how it works without the WIS? :-)
From: Brown, Ben [BAY:NHBED:DS48]
Sent: Tuesday, June 20, 2000 1:39 PM
Subject: Re: Gearbox reality check
It could be the terminology that is confusing the issue. I
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
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
on byte boundaries as indicated by the pointer logic (to
the start of the SPE) but the data it extracts is organized
66-bit words, i.e. it only uses the byte boundaries to find
start and end of the SPE and to separate the OH bytes, while
the content of the SPE is considered a collection of
How close is this?