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Cell Relay Retreat>List Archive>month:1997-Nov> msg00137



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Re: ATM over SDH

  • From: Carl Symborski <carl@umd5.umd.edu>
  • Date: Wed, 19 Nov 1997 18:47:18 -0500 (EST)

On 19 Nov 1997, John van Luijk wrote:
> Can somebody tell the use of setting the path signal label in an SDH path
> to 13. That is the number so SDH knows that he is transporting ATM cells?
> 
> What use is it that SDH knows that the payload is ATM?

The path signal label is used for both SONET (STS) and SDH (STM) standards.
The C2 byte is the path signal label which identifies the construction
and content of a payload envelope (SPE).  This enables end users to
determine how network services (that is, user data flow) were mapped into
the SPE by the transmitter.  One such mapping is for ATM, indicated by a
C2 value of 13 (hex).  The "end user" in this case is the entity which terminates
the path.  So the C2 byte tells this equipment what technique is
needed to extract the user data from the payload envelope. 

I presume there are other mappings.  Anyone know how IP is directly mapped
onto SONET?

Carl Symborski