Microhard Systems MRX-900, Operating Manual

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12 MRX-900 Operating Manual: Configuration Options
In an ideal situation where
the communications link
performs well and there is no
interfering “noise” that can
cause errors, set the
Minimum Size to 0 and
Maximum Size to 255.
3.9 Packet Parameters
Packet Parameters define the characteristics of the internal packets or frames
which are transmitted. The settings should be set only by an expert since
adequate care must be taken to maintain reliability and optimum
performance. .The parameters which can be set are displayed under option 9
in the main menu:
Packet Parameters
1) Minimum Size 0
2) Maximum Size 255
3) Retry Limit 255
4) CRC/Retransmit Enabled
ESC to exit
Select a Parameter to Configure : _
1) Minimum Size
This setting has a range of 0 to 255, and defines the
number of bytes to accumulate from the DTE before transmitting a packet.
Setting this value to 0 ensures that all characters sent by the DTE are
immediately transmitted. The value may not exceed the maximum packet
size.
2) Maximum Size This setting has a range of 1 to 255, and defines the
maximum number of bytes from the DTE which should be encapsulated in a
packet. This value should be greater than the minimum packet size, but not
smaller than is necessary for reliable communications. If the wireless link is
consistently good and solid, a maximum size of 255 is recommended.
However, if the link is poor (
e.g. , experiencing excessive interference) and
data is frequently retransmitted, the maximum packet size should be reduced.
This decreases the probability of errors within packets, and reduces the
amount of traffic in the event that retransmissions are required. Since a
smaller packet size results in a proportionally higher overhead and lower
overall throughput on a good connection, this should only be reduced if many
errors are being detected by CRC (see Radio Statistics option of
configuration).
3) Retry Limit This determines the number of attempts that will be
made to retransmit data which failed the CRC checksum. Once the limit is
reached, the modem will give up and discard the data. If the wireless
connection is poor and data often needs to be retransmitted, a modem could
be “tied up” trying to retransmit, thus holding up pending data. (XXX)
4) CRC/Retransmit
This parameter is either Enabled or Disabled, and
determines whether the MRX-900 will handle error-checking and manage
retransmissions (to guarantee accuracy of data, possibly at the cost of
throughput), or whether these functions will be handled by the software on
each DTE. When this parameter is selected, the following submenu is
displayed:
CRC/Retransmit
* 1) Enabled
2) Disabled
ESC to exit
Select CRC usage : _