From http://www.cisco.com/warp/public/473/53.shtml#frames
Deferred Frames (Out-Lost or Out-Discard)
If you have a large number of deferred frames, or out-lost frames, it means that the switch's output
buffers have filled up and the switch had to drop these packets. This could be a sign that this
segment is running at an inferior speed and/or duplex, or that there is too much traffic going
through this port.
Inferior Speed/Duplex for the Amount of Traffic
Your network may be sending too many packets through this port for the port to handle at its
current speed/duplex setting. This could happen where you have multiple high-speed ports flowing to
a single (usually slower) port. Consider moving the device hanging off this port to faster media
(for example, if the port is 10 Mbps, move this device to a 100 Mbps or Gigabit port), or changing
the topology to route frames differently.
Segment Too Busy
If the segment is shared, other devices on this segment may be transmitting so much that the
switch has no opportunity to transmit. Consider removing some devices off of this segment to another
segment to give the switch more opportunity to transmit.
Applications Being Used
At times the traffic transmission characteristics of the applications being used can lead to this
occurring. NFS file transfers coming from a Gigabit attached server using user datagram protocol
(UDP) and a 32 K window size is one example of an application setting that could bring out this type
of problem. If you have checked or tried the other suggestions (checked speed/duplex, no physical
errors on the link, all the traffic is normal valid traffic, and so on), then reducing the unit size
being sent by the application may help alleviate this problem.
Note: Out-lost is also noted as Out-discard in some platforms.
You can also reference
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/sw5_1/comdref/sh_d_i.htm#xtocid51470 for
more info on "show counters" output.
