ASCOM Myco 3 - Air Traces of 802.11 Traffic

Troubleshooting Tools
TROUBLESHOOTING GUIDE
Ascom Myco 3
• When capturing wireless bear in mind that the capture device has the same limitations as other wireless
devices, that is, it will miss packets, be subjected to disturbances and can be out of range. To ensure the
best possible wireless capture try to place the capture device in between the monitored devices, that is,
between the handset and the AP. Do not place the capture device too close to another wireless device
and keep at least 0.5 m between the capture device and monitored devices. If placed too close, traffic
may be overheard on the wrong channels, for example packets on channel 6 will appear on channel 11,
or not heard at all due to saturated receivers.
• A result without knowing what happened during the capture is of little use. Try to make note of what the
capture is designed to capture and what devices are involved, what devices are present and what was
expected to happen but did not.
• Try not to influence the monitored system. For example, if capturing wired traffic with Wireshark or
OmniPeek, consider disabling name resolution because each IP/name lookup will generate traffic from
your PC to the DNS server.
• If data on one channel is to be recorded the WLAN adapter can only be set to listen to one channel. If
roaming is going to be monitored, two or more channels need to be monitored, in which case one
adapter per channel is required.
5.3 Air Traces of 802.11 Traffic
Ascom recommends Omnipeek from LiveAction as the airtrace tool for capturing data on a designated
channel. The tool can employ several WLAN adapters simultaneously in promiscuous or monitor mode to
capture the data.
If other air trace tools than Omnipeek are used, the traces must be saved in Packet Capture
(PCAP) format. This is a TAC requirement.
Prerequisites
• A support engineer should have already investigated and ruled out relatively easy to identify causes
such as incorrectly configured parameters and incompatible software versions.
• RF problems should also have been investigated and eliminated as a cause of a problem by doing a site
survey.
• Problems like co-channel interference, under- or over-coverage, rogue WLAN transmitters and analog
interference sources should also have been addressed.
It is important to note the following before starting a trace:
• Captured traces might not be 100% true. The trace consists of data heard by the adapters, which may
miss data transmitted by handset or AP. It is therefore recommended to take several captures to ensure
that a complete data flow is logged.
• If more than one handset is used for the trace and the handsets are placed too close together, RF
disturbances between the handsets may occur.
To optimize the trace, ensure that:
• The distance between handset and adapter should be no less than 50cm and no more than 100cm.
• A clear line-of-sight exists between the handset and the adapter.
• The adapter is placed between AP and handset.
If the handset is already experiencing WLAN communication problems, it is not recommended
to enable RPCAP tracing in the Admin menu because this will generate additional WLAN traffic.
20 TD 93297EN / 19 December 2019 / Ver. B