OSI/AS Programming Manual

Sending and Retrieving User Data
APS Procedures Programming Concepts
056783 Tandem Computers Incorporated 2–37
Figures 2-7 through 2-9 illustrate the way in which various combinations of single
ASN.1 and octet-aligned user data elements are packaged into PDV lists in a protocol
data unit (PDU) when sending data. Note that you can spread a single PDV over
multiple user data elements by specifying the same PCID in adjacent elements.
Figure 2-7. Two Single ASN.1 User Data Elements With the Same PCID
User Data Header
Number of Elements = 2
User Data Element Header
PCID = px
Type = Single ASN.1 Type (SAT)
Length = lx
User Data Element Value
PDV (lx)
User Data Element Header
PCID = px
Type = Single ASN.1 Type (SAT)
Length = ly
User Data Element Value
PDV (ly)
APS User Data
PDV list
PCID: px
Type: SAT
Length: lx
PDV list
PCID: px
Type: SAT
Length: ly
PDV (lx)
PDV (ly)
User Data in PDU
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