Avaya BCM 2.0 IP Telephony Manual de usuario descargar pdf (Pagina 33)

Engineering guidelines 33

P0911590 Issue 02 Enterprise Edge 2.0 IP Telephony Configuration Guide

router1 to router4 instead of having the call routed from router1 to router2 to

router3 to router4 reducing the hop count by two.

• Router reduction. Join co-located gateways on one larger and more powerful

router.

Adjust the jitter buffer size

The parameters for the voice jitter buffer directly affect the end-to-end delay and

audio quality. IP telephony dynamically adjusts the size of the jitter buffer to adjust

for jitter in the network. The installer or administrator sets the starting point for the

jitter buffer.

Lower the jitter buffer to decrease one-way delay and provide less waiting time for

late packets. Late packets that are lost are replaced with silence. Quality decreases

with lost packets. Increase the size of the jitter buffer to improve quality when jitter

is high.

IP telephony fax calls use a fixed jitter buffer that does not change the hold time

over the duration of the call. Fax calls are more prone to packet loss. In conditions

of high jitter, increase delay (through the use of a deeper jitter buffer). To allow for

this increase, IP telephony provides a separate jitter buffer setting for fax calls.

Reduce packet errors

Packet errors in intranets correlate to congestion in the network. Packet errors are

high because the packets are dropped if they arrive faster than the link can transmit.

Identify which links are the most used to upgrade removes a source of packet errors

on a distinct flow. A reduction in hop count provides for less occurrences for routers

and links to drop packets.

Other causes of packet errors not related to delay are as follows:

• Bad link quality

• Overloaded CPU

• Saturation

• LAN saturation

• Limited size of Jitter buffer

If the underlying circuit has transmission problems, high line error rates, outages,

or other problems, the link quality is bad. Other services such as X.25, frame relay

or ATM can affect the link. Check with your service provider for information.

Find out what the router’s threshold CPU utilization level is, and check if the router

conforms to the threshold. If a router is overloaded, the router is continuously

processing intensive tasks. Process intensive tasks prevent the router from

forwarding packets. Reconfigure or upgrade the router.

Routers can be overloaded when there are too many high capacity and high traffic

links configured on it. Ensure that routers are configured to vendor guidelines.

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Avaya BCM 2.0 IP Telephony Manual de usuario Pagina 33