CANOGA PERKINS 9145E NID Software Version 4.10 - Manual (Page 94)

9145E NID Software User’s Manual Diagnostics
Network Performance
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ensure that it is possible to revert to an earlier release of the firmware without losing or modifying
the PM Profile and Address parameters.
4.6.11.3 Frame Loss Measurement
SAM supports directional Frame Loss measurement. This means that it is possible to determine
frame loss in the outbound direction, from the local to the remote NID and determine frame loss
in the inbound direction, from the remote NID to the local NID. Remote Frame Loss Ratio
Granularity: SAM test packets are sent from a local unit, reflected by a remote unit, and received
back at the local unit. One thing that is not readily seen is that the number of the packets
reflected by the remote unit is a function of the number of packets that it receives from the local
unit without loss. For example, if the local unit sends 10 packets and two are lost before the
remote can receive them, then the remote will only reflect eight packets.
Measuring Directional Loss
The SAM system uses two methods to help measure the directional frame loss: Test Packet
Content Frame Loss Measurement SAM test packets contain data within the reserved area to
determine in which direction the frames were lost. By using the test packets to support and
transport this data, no additional facilities are normally required in a majority of the cases.
However, if the last packet is lost, then the information contained in that packet about the “frames
received and lost” is also lost.
Out-of-Band Frame Loss Measurement
Because of the issue described under Test Packet Content Frame Loss Measurement, an
alternate method is required to retrieve the frame loss measurements. A special SAM test packet
is used to retrieve the frame loss counters for a test period. This is performed either through the
test network or, if not successful, through the management network. If the frame loss counters
cannot be retrieved through either method, the remote-to-local frame loss measurement is
classified as not available, uses only round trip frame loss, and measures only two-way
availability.