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Cell Relay Retreat>List Archive>month:1998-Jun> msg00157



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Re: Division of work between CS and SAR sublayers in AAL?

  • From: "Nuno Pinto" <eduardo-n-pinto@telecom.pt>
  • Date: Tue, 30 Jun 1998 12:17:35 +0100

Hi Martin!

I don't know if I'm going to help you, but here it goes:
This is from "ATM Switching Systems", Thomas M. Chen and Stephen S. Liu:
 " ... The CS PDUs are then passed to the SAR sublayer and the segment is
prefixed with 1 byte of SAR information consisting of 4 bit sequence number
(SN) and 4 bit sequence number protection (SNP)..."
" ... The purpose of the SN field is to identify the sequential order of SAR
PDUs for reassembly. The SN field consists of a convergence sublayer
indicator (CSI) bit and a 3-bit sewuence count (SC). The CSI bit is actually
reserved for use by the CS. It is used to indicate the existence or absence
of a CS function.The sequence count is assigned to the CS PDUs to detect
lost or misordered PDUs."
 " The SNP field provides the SN field with single-bit error correction or
multiple-bit error detection..."

                                        Bye,
                                            Nuno Pinto