Mitel MiVOICE BUSINESS, Engineering Manualline

Page: 241 / 381

Network Configuration Concepts
227
Since the bandwidth is derived from the number of conversations, it is important to understand
which CODEC is used across the link (G.729a, G.711, or a combination of both).
Also, the level of networking between nodes and whether it includes PSTN trunk traffic or only
internal intercom traffic needs to be understood.
As a general guideline, consider that a single node might have a high networking traffic ratio
of 15%. For a particular node with a number of devices, the amount of traffic to and from this
node remains constant. What differs is the level of traffic destined for another particular node.
For example, 15% of traffic might be destined for the second node in a two-node system, but
7.5% is destined for each of the other two nodes in a three-node system. Obviously, in the
second scenario, less bandwidth is needed to and from a particular node, but the total per node
remains about the same.
A number of factors determine compression operation:
• Are there sufficient resources (i.e. are there enough DSP channels available)?
• Have sufficient compression licenses been acquired?
• Can the end device handle compression? Some phones can handle only G.711.
• See the application information to determine whether compression is handled.
• Is compression enabled in the Class-Of-Service options?
• Are the IP trunks (IP networking routes) configured with compression?
IP NETWORKING LIMIT WORKING EXAMPLE
Consider the following example:
• Two equal-sized systems.
• 250 IP devices/phones.
• Calls from TDM, or to TDM devices including trunks, use G.711 CODEC.
• Calls between IP devices use the G.729a CODEC.
• Traffic is typically 35% (100-65) internal, the remainder to and from PSTN trunks.
• Calls internally are typically 50% outgoing and 50% incoming.
• Traffic is rated at 6 CCS per device.
• Traffic between nodes is 15%.
Note: Music On Hold and messages to and from Voice Mail can be handled with G.729a,
if available.