GE GFK-2489 - Manual (Page 147)

6-14 TranSphere TS Wireless Extended Range IP Networking Transceivers – January 2008 GFK-2489
6
Optimizing Performance
After the basic operation of the radio has been established, you may wish to optimize network
performance using some of the suggestions in this section. The effectiveness of these
techniques vary with the design of your system and the format of the data being sent.
There are two major areas for possible improvement—the radio and the data network. The
following sections provide you with a variety of items to check and on many occasions, ways
to correct or improve their performance.
Principles of Wireless Network Operation
The following points are of value in dealing with the networking aspects of the transceiver.
1. The AP serves as a network bridge
▪ The transceiver goes through a “listening and learning” period at start-up before it
sends any packets over either of its ports. This lasts about 10 seconds after the
CPU operating system finishes its startup cycle.
▪ The bridge code in the transceiver operates and makes decisions about packet
forwarding just like any other bridge. The bridge code builds a list of source MAC
addresses that it has seen on each of its ports. There are a few general rules that
are followed when a packet is received on any port:
▪ If the destination address is a multicast or broadcast address, forward the
packet to all other ports.
▪ If the destination address is not known, forward the packet to all other
ports.
▪ If the destination address is known, forward the packet to the port that the
destination is known to be on (usually the RF port).
▪ The bridge code uses Spanning Tree Protocol (STP) to prevent loops from being
created when connecting bridges in parallel. For example, connecting two
Remotes to the same wired LAN could create a loop if STP was not used. Every
bridge running STP sends out Bridge Protocol Data Units (BPDUs) at regular
intervals so that the spanning tree can be built and maintained. BPDUs are 60-byte
multicast Ethernet frames.
2. Throughput calculations must take into account all overhead.
▪ Throughput over the air is affected by several factors, including: how compressible
the data is, how efficiently the over-the-air bandwidth is used (which varies by
packet size and dwell time), and the quality of the link.