Nortel VoIP Gateway, Configuration Manual

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Measuring Intranet QoS 189
Norstar VoIP Gateway Configuration Guide
The Traceroute program checks if routing in the intranet is symmetric for each source destination
pairs. Also, the Traceroute program identifies the intranet links used to carry voice traffic. For
example, if Traceroute of four site pairs gets the results shown in the following table, you can
calculate the load of voice traffic per link, as shown in the second table.
Adjusting Ping measurements
The Ping statistics are based on round-trip measurements. While the QoS metrics in the
Transmission Rating model are one-way. To make the comparison compatible, the delay and
packet error
Ping
statistics are halved.
Adjustment for processing
The
Ping
measurements are taken from
Ping
host to
Ping
host. The Transmission Rating QoS
metrics are from end user to end user, and include components outside the intranet. The
Ping
statistics for delay requires additional adjustments by adding 140 ms to explain the processing and
jitter buffer delay of the gateways.
No adjustments are required for error rates.
If the intranet measurement barely meets the round trip QoS objectives, the one-way QoS is not
met in one of the directions of flow. This state can be true when the flow is on a symmetric route
caused by the asymmetric behavior of the data processing services.
Table 31 Site pairs and routes
Site pair Intranet route
Santa Clara/Richardson R1-R4-R5-R6
Santa Clara/Ottawa R1-R2
Santa Clara/Tokyo R1-R4-R5-R7
Richardson/Ottawa R2-R3-R5-R6
Table 32 Computed load of voice traffic per link
Links Traffic from
R1-R4 Santa Clara/Richardson
Santa Clara/Tokyo
R4-R5 Santa Clara/Richardson
Santa Clara/Tokyo
R5-R6 Santa Clara/Richardson
Richardson/Ottawa
R1-R2 Santa Clara/Ottawa
R5-R7 Santa Clara/Tokyo
R2-R3 Richardson/Ottawa
R3-R5 Richardson/Ottawa