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Thanks for the response. I have two more questions.
1. I am not sure how that works. So there are some framers in the
doesn't know how to compose concatenated frames, but they can somehow
pass the concatenated payloads in channelized frame format. That's
why we need those 63 columns of fixed stuff?
2. After reading the WIS clause, Here is how I feel. Please
let me know
if I am wrong.
For the transmit process. We always have constant value
of H1, H2 which is 522(right next to J0) and we don't support floating SPE
or pointer justification mechanisms(we expect the rate matching mechanism
in PCS and MAC will take care of the synchronization task).
For the receive process. We still need to support floating SPE and pointer
justification in case the traffic needs to go through LTEs which might change
the starting point of SPE. Or do we?
David Martin wrote:
You're on the right track. The 63 fixed stuff columns are used in conjunction with
the single POH column for interworking with 'virtual concatenation' in SDH. The
-64c signal ('contiguously concatenated') is split up into 64x STM-1s. The original
POH column maps to STM-1#1, with the other 63 fixed stuff columns becoming
the POH columns for STM-1#2 thru 64. Special OH is inserted so the STM-1s
can be consolidated at the rx end back into a contiguously concatenated VC-4-64c.
The reason for this deviousness is that many transport vendors did not support
handling of concatenated payloads with their first (perhaps later versions too)
releases of SDH equipment (i.e. concatenation flag interpretation by the pointer
processor wasn't built in). With the emergence of POS ports, the way around this
was to split up a concatenated signal into its lowest common denominator.
Note that Nortel equipment has always supported contiguously concatenated
From: Louis Lin [mailto:louislin@xxxxxxxx]
Sent: Wednesday, October 25, 2000 8:29 PM
Subject: Question on WIS(clause50).
At page 183, Figure 50-4 : Structure of SPE
My question is : There are 63 columns of fixed stuff in the SPE and
I don't know what's the purpose of that. My guess it's for compatibility
with SDH VC-4-64c. I am not familier with SDH, but does VC-4-64c
need 64 POH columns?