Brocade 6910 Ethernet Access Switch Diagnostic Guide (Supporting R2.2.0.0) - Manual (Page 31)

Brocade 6910 Ethernet Access Switch Diagnostic Guide 21
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DRAFT: BROCADE CONFIDENTIAL
Ethernet diagnostics
A CRC alignment error is generated when the total number of packets received is from 64
through 1518 octets, but contains either a bad FCS with an integral number of octets (FCS
error) or a bad FCS with a non-integral number of octets (alignment error).
• Runts
Any received packet that is less than 64 bytes is illegal, and is called a runt. In most cases,
runts arise from a collision, and although they indicate an illegal reception, they may occur on
correctly functioning networks. The receiving Brocade device discards all runt frames.
• Giants
Any received packet that is greater than the maximum frame size is called a giant. In theory,
the jabber control circuit in the transceiver must prevent any node from generating such a
frame, but certain failures in the physical layer may also give rise to oversized Ethernet frames.
Like runts, giants are discarded by the receiving Brocade device.
• Misaligned frames
Any frame that does not contain an integral number of received octets (bytes) is also illegal. A
receiver has no way of knowing which bits are legal, and how to compute the CRC-32 of the
frame. Such frames are therefore also discarded by the receiving Brocade device.
NOTE
Brocade recommends regular software maintenance and upgrades to keep up with firmware code
updates.