Sierra Wireless DART 200 CDPD Modem Guia do Utilizador descarregar pdf (Página 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

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.

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