Ref: 99980081
Title: Gathering Network Statistics from the IB/1 and IB/2
Date: 4/1/87

Copyright 3Com Corporation, 1991.  All rights reserved.

The IB/1 and IB/2 are Bridge Commuications' high-performance,
data link level bridges that provide protocol-transparent
routing.  They feature adaptive learning and ISO layer 2
statistics gathering.  However, because they are protocol
transparent, they do not provide the XNS or TCP/IP Network
Control Servers with audit trail information.  In the XNS
environment, it is easy to REMOTE to the IB and show statistics.
In the TCP/IP environment, the IB console port can be attached to
a TCP/IP Communications Server's terminal port.  When displayed,
these statistics would appear like this:

Remote: sh ns 0

                                 Network 0 Statistics
RcvPackets  RcvBytes     MCPkt   BCPkt   Crc   Frame   Long    LostP
----------  ----------   ------  ------  ----- ------- ------- -----
3901869     476859391    110     40743   0     2       0       0

XMTPackets  XmtBytes   MCPkt  BCPkt  Defer 1Coll MColl LColl EColl NetErr
----------  ---------  -----  -----  ----- ----- ----- ----- ----- ------
62206       3809418    0      31519  176   418   62    0     0     0

The IB statistics include:

CRC (Cyclic Redundancy Error) - computed as the bits are sent and
is appended at the end of the out-going frame.  On reception, the
CRC computation should give a known result; otherwise an error is
indicated.

Frame - the Ethernet controller chip can handle up to 7 dribbling
bits when a received packet terminates.  During reception, the
CRC is generated on every serial bit (including the dribbling
bits) coming from the cable, and is stored internally.  The
framing error is reported to the user as follows:

*   If there are 1 to 7 dribbling bits and there is no CRC
error, there is no framing error.

*   If there are less than 8 dribbling bits and there is a
CRC error, there is also a framing error.

*   If there are no dribbling bits, there is no framing
error.  There may or may not be a CRC error.

Long (illegal length) - packet is rejected for being over 1528
bytes.  Packets under 64 bytes are also rejected but are not
counted.

1Coll - a collision that occurs within 6 byte times (4.8ms) wil
result in the packet being rejected because of an address
mismatch.  This counts the number of frames that required one
retry.

MColl (multiple collision) - with a collision that occurs within
a 64 byte time (51.2ms), the controller will attempt to retrieve
it 15 more times.  This counts the number of frames that required
between two and fifteen retires.

LColl (late collision) - a collision that occurs after 64 byte
times resulting in a truncated packet.

EColl (excessive collision) - if all 16 attempts at transmission
fail, the chip gives up ownership of this packet and processes
the next packet.

NetErr - IECM: loss of carrier bit set after the packet has been
transmitted.  IBCM: loss of CRS during packet transmission.

Defer (not an error) - deferred because of traffic on the link.

Lost - records the number of correct incoming frame discarded due
to lack of memory resources (buffer space or received frame
descriptors) or due to the fact that the memory bus was not
available in time to transfer them.

        TRANSMIT ERRORS               RECEIVE ERRORS
        ---------------               --------------

             1Coll                         CRC
             MColl                         Frame
             LColl                         Long
             EColl                         Lost
             NetErr
             Defer







