NS3000/iX Operations and Maintenance Reference Manual (36922-90042)

224 AppendixA
LINKCONTROL Command
NS 3000/iX LAPBMUX Link Statistics
normal priority.
Receive overruns — Total number of frames that were deferred to
other network traffic before their initial transmission onto the network.
This means that the 100Base-T card had to wait for carrier to drop and
stay dropped for a few nanoseconds, before attempting to transmit the
frame. The maximum printable value of this 64-bit field is 17 digits, or
about 99 million billion frames. In the previous example, 1738 transmit
frames were deferred.
Recv dropped: buffer — Total number of frames received from the
adapter card, but dropped because no data buffers were available from
the upper layer protocol requesting to receive these frames. This is a
relatively common occurrence, amounting to flow control for all
protocols sharing those buffers. Many protocols include built-in
mechanisms for detecting lost frames and requesting their
retransmission from the remote side. The maximum value of this 32-bit
field is 2147483647. In the example above, out of 66.4 million frames
received, 262 have been dropped for lack of buffer resources; any
similar level would be considered normal.
Recv dropped: addr — Total number of frames received by the
adapter card, but dropped because no upper layer protocol had
requested future reception of those frames, or because that protocol
unbound itself from the link while the received frame was still in
motion. Older, intelligent adapter cards can invisibly receive and drop
these frames, often without ever reporting them as statistics. But
today’s adapters are not intelligent, and require link driver
involvement. For users unfamiliar with seeing it, this statistic may
seem excessive. But it is important because it gives an indication of the
amount of unnecessary traffic present on the network segment to which
the adapter card is connected. High values may indicate a need to
resegment the network, since systems and their adapters are spending
a large amount of time and resources recognizing and dropping frames
they do not care to see. High volumes of such traffic can also limit
network bandwidth. The maximum printable value of this 64-bit field is
17 digits, or about 99 million billion frames. In the previous example,
out of 15.7 million frames received, 9.87 million have been dropped
based on address: about 63% of all frames received are then being
dropped. This level would be considered high.
Recv dropped: other — Sum total number of frames received from
the adapter card, but dropped because: an upper layer protocol error
was returned; the required address format was not supported; the
frame arrived while the link driver was in an unusual state; or for
perfect multicast filtering reasons. The maximum value of this 32-bit
sum is 2147483647. In the example above, 24785 frames have been
dropped for one or more of the reasons listed; this number would be
considered high, and further investigation might be needed if it appears
to be impacting any applications.