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

Appendix A 215
LINKCONTROL Command
NS 3000/iX 100Base-T Link Statistics
CRC or Maxsize error — Number of cyclic redundancy check (CRC)
errors or oversized frames that were seen during reception by the link.
A CRC error indicates that the frame was checked using CRC-32
frame-checking, but that the value obtained by the CRC did not match
the CRC value contained at the end of the frame. CRC errors do not
include frames having alignment or coding errors. Oversized frames are
those longer than 1518 bytes. These adapter card statistics are
periodically read, and are accumulated by the link driver. The
maximum value of this 32-bit field is 2147483647. A nonzero value in
this statistic could indicate a defective cable, adapter, or hub, a loose
connection, presence of severe electrical noise along the cable path, or a
misbehaved application, adapter, or hub at the transmission end. For
PCI 100Base-T, these statistics (CRC error, Maxsize error) are reported
separately by the adapter card and are displayed separately (Recv CRC
error, Recv Maxsize error).
Code or Align error — Number of frames received with an alignment
error (not an even multiple of 4 bits of data) or code errors (an error
signal was received from the 100Base-T receive hardware). These
adapter card statistics are periodically read, and are accumulated by
the link driver. The maximum value of this 32-bit field is 2147483647.
This statistic is not applicable to PCI and is not displayed for PCI
100Base-T links. If alignment errors occur frequently, one of the
following may be the cause:
• A 100Base-T adapter card is not operating to within 802.3
specifications.
• A 100Base-T hub is performing poorly.
• The 100Base-T cable is not CAT-5 grade.
• A section of 100Base-T cable contains wire pairs which are not
properly twisted, paired, or of equal length.
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