User's Manual Part 1

100 APCD-LM043-8.0 (DRAFT C)
6: Installation & Diagnostic Tools
Table 16 Signal Quality Checks
6.6 Testing Connectivity Using the Ping Utility
The CCU and EUM include a ping utility to test for network connectivity, latency, and packet
loss. The ping command sends an ICMP echo request to a specific destination and reports the
round-trip time, number of bytes sent, and success or failure.
Installation testing requires you to use both short and long packet pings to confirm satisfactory
packet error rates over the radio link. You can run this test from the command prompt at the
customer PC connected to an EUM, assuming the PC is available and properly connected to
the EUM.
The ping test accepts up to three arguments:
• address
• length (default is 64 bytes)
• interval (in milliseconds) (default is 490 milliseconds)
Enter the command arguments in the following order: ping <destination> <length> <interval>.
If you omit either <length> or <interval>, the command will use the default settings.
Measuring Active Latency of a Connection
The standard DOS ping test transmits subsequent pings at one second intervals. Given the
design of the Polling MAC, which moves an EUM from active to inactive status after 500
milliseconds of inactivity, this standard ping test does not accurately measure the connection
latency for an active EUM. The ping utility on the CCU and EUM allows you to configure the
time interval between repeated pings. The default time interval between pings on CCUs and
EUMs is 490 milliseconds, less than the 500 millisecond interval after which the EUM status
becomes inactive. This time interval allows the ping test to accurately measure the active
latency of the connection.
Retry
Rate
Average
SQ
RNA
RNB
RSSI Indication
High < 8 < 20 Low
(<-80 dBm)
Poor signal.
High <
8 < 20 Good
(>-80 dBm)
Possible multipath or interference. If RNA
and RNB are different, they may give an
indication of the direction of the interferer.
High > 8 < 20 Good Possible severe multipath or interference
problem.