CANOGA PERKINS 9145E NID Software Version 4.10 User Manual
Page 91
Diagnostics
9145E NID Software User’s Manual
Network Performance
79
1. Test packets are sent at regular intervals as specified by the Sample Period.
2. N test packets are grouped together into ∆t as specified by the NTP (∆t time).
3. A Frame Loss Ratio (FLR) is computed for each ∆t as follows:
•
Packets Lost = Packets Sent – Packets Received
•
FLR = Packets Lost / Packets Sent
The granularity of this computation is governed by the number of packets in ∆t. For example, if
the NTP is 2, the possible FLR values are 0, 50 and 100.
The FLR computation can be for a Round Trip (RT) or One Way for Local to Remote (LR) or One
Way for Remote to Local (RL). One Way verses Round Trip FLR is available as defined in the
following scenarios:
•
One Way:
•
Both the Local and Remote NIDs have a NPA-SAM license, and there is sufficient test
data available from which FLR can be calculated in both LR and RL directions.
•
Round Trip:
•
The Remote NID does not have a NPA-SAM license.
•
Both the Local and Remote NIDs have a NPA-SAM license, however, due to lost pack-
ets (insufficient test data), the Master NID is unable to calculate both LR and RL FLR.
In this case, One Way is downgraded to a Round Trip FLR measurement.
4. New state is computed as follows:
•
If the current state is Available, the formal description is:
If all FLRs within the Service Availability Window are greater than or equal to the
Cu, then the new state is Unavailable. If any of the FLRs are less than the Cu
than the new state is Available.
•
If the current state is Unavailable, the formal description is:
If all FLRs within the Service Availability Window are less than or equal to the Ca
than the new state remains Unavailable. If any of the FLRs are greater than the
Ca than the new state remains Unavailable.
An example:
•
Data Definitions
•
Sample period = 1
•
∆
t = 2
•
Service Availability Window = 4 ∆t
•
Ca = 23
•
Cu = 79
•
Current State = Available
•
FLRs = {0,50,100,50,100,100,100,100,50}
•
The first Service Availability Window consists of the first four FLRs {0,50,100,50}.