82596DX Datasheet, PDF (23/77 Pages) Intel Corporation – HIGH-PERFORMANCE 32-BIT LOCAL AREA NETWORK COPROCESSOR

82596DX SX
NETWORK PLANNING AND
MAINTENANCE
To properly plan operate and maintain a communi-
cation network the network management entity
must accumulate information on network behavior
The 82596 provides a rich set of network-wide diag-
nostics that can serve as the basis for a network
management entity
Information on network activity is provided in the
status of each frame transmitted The 82596 reports
the following activity indicators after each frame
 Number of collisions The number of collisions
the 82596 experienced while attempting to trans-
mit the frame
 Deferred transmission During the first transmis-
sion attempt the 82596 had to defer to traffic on
the link
The 82596 updates its 32-bit statistical counters af-
ter each received frame that both passes address
filtering and is longer than the Minimum Frame
Length configuration parameter The 82596 reports
the following statistics
 CRC errors The number of well-aligned frames
that experienced a CRC error
 Alignment errors The number of misaligned
frames that experienced a CRC error
 No resources The number of frames that were
discarded because of insufficient resources for
reception
 Overrun errors The number of frames that were
not completely stored in memory because the
system bus did not keep up with incoming data
 Receive Collision counter The number of colli-
sions detected during receive Collisions occur-
ring before the minimum frame length will be
counted as short frames Collisions in the pream-
ble will not be counted at all
 Short Frame counter The number of frames that
were discarded because they were shorter than
the configured minimum frame length
Once again these counters are not updated until the
82596 decodes a destination address match
The 82596 can be configured to Promiscuous mode
In this mode it captures all frames transmitted on the
network without checking the Destination Address
This is useful when implementing a monitoring sta-
tion to capture all frames for analysis
A useful method of capturing frame headers is to
use the Simplified memory mode configure the
82596 to Save Bad Frames and configure the
82596 to Promiscuous mode with space in the RFD
allocated for specific number of receive data bytes
The 82596 will receive all frames and put them in the
RFD Frames that exceed the available space in the
RFD will be truncated the status will be updated
and the 82596 will retrieve the next RFD This allows
the user to capture the initial data bytes of each
frame (for instance the header) and discard the re-
mainder of the frame
The 82596 also has a monitor mode for network
analysis During normal operation the receive func-
tion enables the 82596 to receive frames which pass
address filtering These frames must have the Start
of Frame Delimiter (SFD) field and must be longer
than the absolute minimum frame length of 5 bytes
(6 bytes in case of Multicast address filtering) Con-
tents and status of the received frames are trans-
ferred to memory The monitor function enables the
82596 to simply evaluate the incoming frames The
82596 can monitor the frames that pass or do not
pass the address filtering It can also monitor frames
which do not have the SFD fields The 82596 can be
configured to only keep statistical information about
monitor frames Three options are available in the
Monitor mode These modes are selectable by the
two monitor mode configuration bits available in the
configuration command
When the first option is selected the 82596 receives
good frames that pass address filtering and trans-
fers them to memory while monitoring frames that
do not pass address filtering or are shorter than the
minimum frame size (these frames are not trans-
ferred to memory) When this option is used the
82596 updates six counters CRC errors alignment
errors no resource errors overrun errors short
frames and total good frames received
When the second option is selected the receive
function is completely disabled The 82596 monitors
only those frames that pass address filterings and
meet the minimum frame length requirement When
this option is used the 82596 updates six counters
CRC errors alignment errors total frames (good and
bad) short frames collisions detected and total
good frames
When the third option is selected the receive func-
tion is completely disabled The 82596 monitors all
frames including frames that do not have a Start
Frame Delimiter When this option is used the 82596
updates six counter (CRC errors alignment errors
total frames (good and bad) short frames collisions
detected and total good frames
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