Outbound Packet Generation Options (<packets> section)

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The challenge of sending the data from the application to the DS is in deciding how to group this data into the network packets of reasonable size. Carrying too little data in each packet increases network load while sending packets with too much data slows down the delivery of this data to the DS. <Packets> section contains parameters that define how the VSP will divide the "serial" data sent by the application into network packets.

 

To give you a better understanding of the options available in this section we will use the concept of data blocks. Many serial systems use some sort of communication packets (we will call them data blocks to avoid possible confusion with network packets). Since the data block is a basic unit of data transmission in such systems it is only logical to divide the data sent by the VSP into network packets basing on these data blocks.

 

Parameters in the <packets> section allow you to define conditions that "open" the data blocks (see starton and startchar), "close" the data block (stopchar), and "break" the data block into smaller chunks of data without closing the block (maxlen, maxdelay). The VSP ignores all the data received from the application past the end of the previous data block and before the beginning of the next data block (this means, the data is not even recorded into the TX buffer). The VSP sends out the data in the TX buffer as soon as the break or close condition is encountered.

 

Of course, not all systems rely on formatted data blocks, many just send unformatted "random" data. This data can be viewed as one endless data block that starts on the first character received from the application. 

 

The section has the following syntax (purple marks default values that will be used if corresponding parameter is omitted):

 

<packets [maxlen="len(1024)"] [maxdelay="delay(0)"] [starton="any|char"] [startchar="hex"] [stopchar="hex"]/>

 

Click on the links above to jump to individual parameter description topics.

 

Note, that default values of this section's parameters will work fine for most applications. Therefore, simply defining this section as <packets/> will (most probably) be OK.