NS3000/iX Operations and Maintenance Reference Manual (36922-90039)

184 AppendixA
LINKCONTROL Command
NS 3000/iX LAN Link Statistics
Carrier losses. The Carrier losses field indicates that the transmitting
node turned off the carrier signal on the cable. This occurred for one of
the following reasons:
• The stub cable is not connected to the frontplane connector.
• The AUI (or AUI pigtail for ThinMAU) is not connected to the stub
cable.
• The MAU is broken.
• If using thick LAN cable, there may be a short close to the MAU
(ThinLAN cable shorts show up as a retry error as described in the
Transmits 16 collision field description).
If the LAN continuously loses carrier, the problem is probably caused
by a disconnected AUI or stub cable. Make sure that all connectors from
the frontplane of the LAN hardware card to the MAU are connected
securely.
NOTE Collisions occur on IEEE 802.3 Local Area Network (LAN) links
whenever two nodes on the link attempt to transmit data at the same
time. When a collision occurs, the nodes which were involved in the
collision each wait a random amount of time, called random backoff,
before attempting to again transmit the packet along the link. If
collisions continuously occur, check the terminators. Many of the fields
described in this section are incremented whenever a collision occurs.
Transmits 1 retry. This field indicates the number of frames that
collided once before being transmitted successfully. This means that the
random backoff strategy was only used once.
Reflectometer (CIO card only). The reflectometer field is similar in
function to a TDR (Time Domain Reflectometer). The statistic holds the
time count between the pulse and a reflection. Whenever a retry error
occurs, the time in bit times (100ns) from when the frame started to
transmit until the collision occurred is stored by this statistic. This can
be useful for grossly determining the location of an opening in a cable,
or possibly, a short in a ThinLAN cable. This field is erased after every
transmit and is not updated after an external loopback frame is
transmitted onto the link.
While this statistic may aid in pinpointing a problem without the need
to do an actual TDR test, it should be noted that this statistic calculates
the distance using a rough estimate (bit time) and can be inaccurate.
This statistic should never be used as the only means of locating a cable
fault. However, if this field is not equal to 0, then the hardware of the
node is a likely cause of the failure.