Enough Link Capacity; Not Enough Link Capacity; Other Intranet Resource Considerations; Table 29 Link Capacity Example - Nortel VoIP Gateway Configuration Manual

162 Additional feature configuration

Enough link capacity

The following table sorts the computations so that for each link, the available link capacity is
compared against the additional IP telephony load. For example, on link R4-R5, there is capacity
(568 kbit/s) to allow for the additional 96 kbit/s of IP telephony traffic.

Table 29 Link capacity example

Link
End Capacity
Points kbit/s
R1-R2 1536
R1-R3 1536
R2-R3 1536
R2-R4 1536
R4-R5 1536
Some network management systems have network planning modules that determine network
flows. These modules provide more detailed and accurate analysis because they can include
correct node, link and routing information. They also help to determine network strength by
conducting link and node failure analysis. By simulating failures, re-loading network and
re-computed routes, the modules indicate where the network can be out of capacity during failures.

Not enough link capacity

If there is not enough link capacity, consider one or more of the following options:
• Use the G.723.1 codec. Compared to the G.729 codec with 20 ms payload, the G.723.1 codecs
use 29% to 33% less bandwidth.
• Upgrade the bandwidth for the links.

Other intranet resource considerations

Bottlenecks caused by non-WAN resources do not occur often. For a more complete evaluation,
consider the impact of incremental IP telephony traffic on routers and LAN resources in the
intranet where the IP telephony traffic moves across LAN segments that are saturated, or routers
whose central processing unit (CPU) utilization is high.
P0606298 02
Utilization (%)
Available
capacity
Threshold Used kbit/s
85 75 154
85 48 568
Incremental IP telephony load
Site pair
Santa Clara/Ottawa
Santa Clara/Tokyo
Santa Clara/Richardson
Ottawa/Tokyo
Santa Clara/Tokyo
Traffic Enough
kbit/s capacity?
15.5 Yes
24 Yes