Chapter 10: Troubleshooting
The next most frequent source of problems generally arises from
faulty cabling or connectors
or incorrect
cable type. Cabling must be UTP5 or better for LAN and 75-Ohm rather than 50-Ohm for TDM. If long
TDM cable runs or an electrically noisy environment exists, high-quality coaxial cable will be required.
The least frequent cause of problems will be the hardware of the Monitor itself. This statement is not due to
a narcissistic point of view, but rather to the simplicity of configuration features on the Monitor and the
low-component count. A microwave radio link, for example, has waveguides that can fill with water,
antennas that can become misaligned, foreign objects that can block the path. From a failure point of view,
the Monitor is a simpler device.
Performance
Performance issues are addressed in the prior chapters.
Interoperability
The interoperability section of this manual should be reviewed to ensure that appropriate equipment is
connected to the Monitor. Connected LAN equipment should adhere to 802.3 standards.
Pinging
Ping is not reliable
. The protocol which ping programs use does not guarantee delivery of the data
packets.
Ping programs from major software and hardware corporations are known to contain bugs,
both in packet content and function
. Generally, however, nearly all of the ping packets on a test network
that is not over-loaded should get through; if fewer are received, there is probably a problem.
The ping program is a useful, simple test for a TCP/IP Ethernet network. It is a program that sends a data
packet from a source machine to a destination machine, which then returns a response packet. There is a
plethora of information about ping and the free public-domain ping utilities available. Ping is often
supplied as a standard operating system utility, and often the command “ping” followed by the destination
machine's IP address or hostname is all that is required to be typed at the source machine's command line.
The default ping generates approximately one 64-byte packet per second. This is not a robust test. If
convenient, locate a ping program or set command line parameters to generate perhaps 50 pings per second
and try both small packets and large 1400-byte packets. Be aware that packets larger than 1400 bytes
sometimes uncover bugs in the software of ping programs.
Step-by-Step Diagnosis
This section assumes that communication between two machines at opposite ends of the E3, T3/DS3 link
(herein the link) is failing. If this is a test in the laboratory or without a TDM circuit present, be sure to read
the previous “Laboratory Testing” section first.
1. If access to the HTTP management interface of the Monitor is possible, many useful status messages
will be displayed. Typically, any message highlighted in orange should be of concern. Error counters
are of lesser concern if they are not incrementing, and some link errors would be normal as link cables
are initially connected.
The DS3/E3
BER
light of the Monitor should be illuminated and green
. This indicates that a valid,
DS3/E3 waveshape is being received without bit errors and with proper framing. Refer to the front
panel section of this document for other light colors.
The DS3/E3
port
light of the Monitor should be illuminated and green
. This indicates that a valid,
carrier signal is being received on the WAN. Refer to the front panel section of this document for other
light colors.
17
