Maximizing Tcp/Ip; Maximizing Via Setup; Use Router Mode - Cal Amp Dataradio HiPR-900 User Manual

Wireless radio modem

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7.3

Maximizing TCP/IP

If after optimizing the airlink there still appears to be an unexplained speed loss (less than the HiPR-900

radio modem limit of about 40 Kbytes/sec total for both directions), you can look at maximizing TCP/IP.

TCP/IP throughput can be tricky to measure as performance is related not only to the RF link, but how

well flow control is implemented in the TCP/IP stack and how each application is designed. The HiPR-

900 has been highly optimized with this in mind. When the TX/RX LED flashes amber, this not only in-

dicates that data is moving but also indicates (by the LED OFF periods) when data is not moving across

the RF network at full rated speed. If you get flashing RED indications on the TX/RX LED, RF reception

problems are present and causing some loss of throughput. OFF periods indicate that the application has

not presented data to the HiPR-900 radio modem.

Using different client/server combinations or applications may show improvements. For instance, one

FTP server may work 30% faster than another, simply because the buffer management is quicker to re-

spond or has bigger message buffers – yet run at nearly the same speed over a pure Ethernet (no RF) link.

Network Address Translation (NAT), payload data compression and encryption have little effect other

than adding a small latency to the flow of traffic.

The TDD mode should be left enabled unless highly specialized protocols are being run. Sometimes,

these protocols and TDD interfere which each other and may run somewhat faster with TDD disabled.

7.4

Maximizing via Setup Pages

Further performance optimization can be done via the User Interface Setup pages. The fundamental ad-

justments described in the following paragraphs can be changed singularly or in conjunction with each

other

Note:

Data Compression (section 6.7.3.5 above) should only be OFF while testing, thereby eliminating

performance differences due only to different compression rates.

Selecting Router mode (see section 6.7.2.1) is highly recommended when running over a weak RF link.

This mode ensures that several levels of retry mechanisms are at work, each optimized to minimize TCP

flow control delays or even preventing a dropped TCP/IP link. It requires some IP route planning to and

from the HiPR-900 units but is well worth the increase in link stability over the simpler bridge mode.

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HiPR-900 User Manual

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