Re: A Minor NIT
Wesley has a point for an STS-192c payload. Please
note small c for SONET concatenation.
Sorry if I confused anyone with my original note, of this morning,
which was referring to and STS-1 payload.
As STS-192 payload, concatenated or not, features 3 * 192 = 576
columns of overhead, and 192 * 87 = 16,704 columns of payload
for a total of 17,280 columns, and of course 9 rows.
For concatenated payloads, such an STS-192c, the pointers
must also be multiplied, by 192 in this case, to allow them a radius
which covers the span of the entire payload.
So yes pointer adjustments do occur in increments of
192 bytes for an STS-192c frame! But how?
For an STS-192c a positive pointer adjustment will add 192
stuff bytes to this SPE, and thus delete 192 payload bytes from this SPE.
A negative pointer adjustment will delete 192 stuff bytes, and thus add
192 payload bytes to this SPE. These stuff bytes are stored in each of
the 576 H3 bytes in the Line Overhead. Please note that in either case
all of the payload bytes get there, eventually.
Rich & Tom,
I had thought I understood pretty much everything, but now on the
issue of pointer adjustment, there may be a problem. As I understand
this, if there is a positive adjustment, there is need to to
byte stuff (or is it 192 * bytes?). But since the SPE is composed of
66-bit code words, how can we stuff the SPE by the 192 bytes. Pls
correct me if my understanding is wrong.
Very well said. You echo my understanding also. This implies that SONET/SDH
pointer adjustment, while operating on byte boundaries, is 100% compatible
an SPE payload that is on 66-bit boundaries. Does anyone out there disagree