DCS 300 User’s Manual
C-6
How the DCS 300 Routes Transactions
Transactions have a well-defined structure consisting of a header and data. The header
contains a transaction ID, which the DCS 300 uses to determine the destination for a
transaction. The transaction ID is the primary routing mechanism used by the DCS 300.
When the DCS 300 receives a transaction, it checks the system message flag. If the
transaction is a system transaction, it is executed immediately. If the transaction is a
data transaction, the DCS 300 routes the transaction by examining the transaction
header:
•
If the destination field in the transaction header contains a name, the DCS 300
treats the transaction as if it came from an application. It uses the destination name
to forward the transaction to the correct application or device.
•
If the destination field in the transaction header is blank, the DCS 300 uses the
transaction ID field of the header to determine where to send the transaction.
To ensure data integrity, a handshake is built into the routing system. When the
DCS 300 delivers a transaction to a destination, it retains a copy of the transaction until
the application sends back an ACK transaction. This ACK transaction is received by
the ACK channel and it tells the DCS 300 that the application has responsibility for the
transaction. Only then does the DCS 300 discard its copy and send another transaction
to the application. Hot Standby logic controls how long the DCS 300 waits for an ACK
transaction and what it does with other transactions while waiting.
Routing Transactions From Applications
The DCS 300 can route transactions from applications to devices or to other
applications.
These transactions contain a logical name for the destination. The logical
name is either the name of an application or the name given to a device.
The DCS 300
searches through internal tables that are created from the run-time configuration to find
all the correct information about the destination.
If the destination is a device, the message handler determines the name of the
DevComm that is servicing that device and forwards the transaction to it. The
DevComm receives the transaction, translates the logical name into a physical device
address, strips the header from the transaction, and transmits the data to the device.
If the destination is another application, the routing process is more direct: the message
handler only needs to know if the receiving transaction is active or inactive.
Summary of Contents for DCS 300
Page 1: ...P N 067296 005 User s Manual DCS300 ...
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Page 23: ...Getting Started 1 ...
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Page 43: ...Learning About the DCS 300 2 ...
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Page 68: ...blank ...
Page 69: ...Connecting to the Upline Network 3 ...
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Page 94: ...blank ...
Page 95: ...Connecting to the Intermec RF Network 4 ...
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Page 134: ...blank ...
Page 135: ...Connecting to the 9180 and the Intermec CrossBar Network 5 ...
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Page 159: ...Running Data Collection Browser 6 ...
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Page 171: ...Running Terminal Emulation 7 ...
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Page 209: ...Running Peer to Peer Applications 8 ...
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Page 233: ...Running Terminal Sessions 9 ...
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Page 259: ...Running Screen Mapping 10 ...
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Page 269: ...Running Screen Mapping 10 11 10 Screen 3 Screen 4 Main Host Screen Screen 5 ...
Page 333: ...Troubleshooting 11 ...
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Page 373: ...Specifications and Other Helpful Information A ...
Page 374: ...DCS 300 System Manual B 2 blank ...
Page 391: ...Upgrading the DCS 300 and Devices B ...
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Page 411: ...How the DCS 300 Routes Transactions C ...
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Page 431: ...Index I ...
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