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RE: 66-bit alignment vs 8-bit alignment

Title: RE: 66-bit alignment vs 8-bit alignment


My comments are interlaced below.

The SONET section framer does not care about the contents of the SONET path. It
is the circuitry that recovers the payload from the SONET path that is simpler if that
payload is byte aligned, since the byte alignment is already provided by the section

Examples of payload delineation mechanisms, which occur after SONET section
framing and after SONET pointer processing to locate the SONET path: (a) 64B/66B
case - hunting for the 2 bit 01 or 10 pattern every 66 bits; (b) <length><type><HEC>
case - hunting for an 8 byte string which has a CRC-16 which matches the 2 byte value
following the 8 byte string. Case (a) requires searching by bit. Case (b) requires
searching by byte.

See above. Please excuse my terminology.

The slipping operation is performed on link synchronization. Of course that circuitry
is still there after link sync is achieved, it's just burning power. Your reference
to the byte pattern search is the SONET section framer operation, which is common
for either 64B/66B or <length><type><HEC> mappings into a SONET path.

Is it clearer now?


David W. Martin
Nortel Networks
+1 613 765-2901  
+1 613 763-2388 (fax)