* Wi-Fi troubleshooting: Occasionally, you’ll need to leave your chair
As you likely know, Wi-Fi networks are trickier to troubleshoot than wired LANs. One well-known reason is that the network access medium—the unlicensed airwaves—is intermittently subject to interference. “Noise on the line” that may be impeding performance at one moment may not be there the next, making it difficult to pinpoint and fix.
A related issue is that you can’t trace a cable from a device to a switch port in a wireless LAN to easily determine relationships between client and receiver. Rather, wireless communications radiates in three dimensions. While wireless performance monitors may show errors, it’s hard to know where those errors actually occurred.
Errors get reported at the spot where your wireless sensor collects them, but that may not be where they actually take place, points out Scott Haugdahl, CTO at WildPackets, a wired/wireless network performance monitoring company.
He says that, in order to maintain some semblance of control over your data rates, it’s more accurate to count retransmissions, which indicate that a sender did not receive an ACK from the receiver and that a packet was not delivered. The key is to find out why, so you can adjust your environment to run at the data rate speeds you specify.
Finding these inconsistent flukes in the network usually requires a mobile troubleshooter with a handheld analyzer physically “sniffing out” the trouble spot, says Haugdahl. While distributed sensors reporting to a centralized monitoring system should supply the majority of Wi-Fi troubleshooting information you need, it isn’t practical to think you’ll never have to walk the corridors as conditions change, he says.
This raises a question: Is it always desirable to set all nodes at the maximum possible data rate? As a general rule, the answer is yes. However, 802.11 devices have a property called adaptive rate selection – whereby they fall back to multiple transmission rate levels, depending on conditions – for a reason. Next time, we’ll look at some of the considerations, pro and con, about tuning your Wi-Fi devices to always transmit at the highest rate.
