Sierra Wireless DART 200 CDPD Modem - Manual (Page 118)

DART 200 CDPD Modem User’s Guide 8 Application Programming
Sierra Wireless, Inc. 8-24
1. If your application involves transmitting relatively large data files,
test the data transfer using a variety of block sizes. Begin with the
large blocks preferred by your customer. Get some throughput
timings and develop an average. If operating in a sniff-and-hop
CDPD environment, there can be significant variation in the timings.
If CDPD operates on dedicated channels variations are much less.
2. Do enough tests to get a meaningful average. If your application
operates at specific times of the day in a sniff-and-hop environment,
only test during the times the application normally operates.
3. Start dropping the blocksize and repeating the analysis. A plot of
blocksize versus time to complete the file transfer shows a low point
somewhere between the extremes. For example, start with a 1200
byte blocksize, and drop it by 200 until you hit 200. Explore the low
point; the real low might be at 337 bytes, or 489.
4. Once the best point from a throughput perspective is found, ask your
carrier for a protocol trace of the transfer to determine actual byte
counts. Again, try several, since variations in timing usually imply
variations in byte count. To ensure that the best point also has the
lowest byte counts, trace some tests with larger and smaller
blocksizes.
Modem dial directory
To help minimize entering IP Addresses, which with port numbers can
be quite long, the DART 200 offers a dial directory to store up to 10
entries. Refer to &Z command in Appendix F, DART AT Command Set.
These addresses are referenced by slot number (0 to 9) and can be used
for dialing (ATDTSn or ATDPSn), pinging (AT*PSn), or specifying
friendly IP Addresses for the friends only feature.
Make entries with the AT&Zn= command, and view the directory with
the AT&Z? command, as shown in Figure 8-1.
Figure 8-1. Viewing the IP Address directory
AT&Z?
&Z0: 166.174.113.27/1200
&Z1: 166.174.44.13
&Z2: 166.174.113.63/2100
&Z3:
&Z4:
&Z5:
&Z6:
&Z7:
&Z8:
&Z9: 166.174.113.31/2100
OK
? ?
NOTE:
Bigger is not
necessarily better when
it comes to data transfer
block sizes. Take time to
test and analyze your
situation for optimum
results.
? ?
NOTE:
Entries do not need to
be sequential, and port
numbers are not
required (except for dial
addresses). Also, having
a port number does not
prevent an entry from
being used for pinging
or as a friendly address.