Avaya BCM 2.0 IP Telephony Manual de usuario descargar pdf (Pagina 32)

32 Engineering guidelines

Enterprise Edge 2.0 IP Telephony Configuration Guide P0911590 Issue 02

Queuing delay

The queuing delay is the time it takes for a packet to wait in the transmission queue

of the link before it is serialized. On a link where packets are processed in a first

come first served order, the average queuing time in ms and is the result of the

following formula:

Note: where p is the link utilization level.

The average size of intranet packets carried over WAN links generally is between

250 and 500 bytes. Queueing delays can be important for links with bandwidth

under 512 kbit/s, while with higher speed links they can allow higher utilization

levels.

Routing and hop count

Each site pair takes different routes over the intranet. The route taken determines

the number and type of delay components that add to end-to-end delay. Sound

routing in the network depends on correct network design.

Reduce link delay

In this and the next few sections, the guidelines examines different ways of reducing

one-way delay and packet loss in the network.

The time taken for a voice packet to queue on the transmission buffer of a link until

received at the next hop router is the link delay. Methods to reduce link delays are:

• Upgrade link capacity to reduce the serialization delay of the packet, but more

so, reduces the utilization of the link, reducing the queueing delay. Before

upgrading a link, the installer or administrator must check both routers

connected to the link for the upgrade and ensure correct router configuration

guidelines.

• Change the link from satellite to terrestrial to reduce the link delay by on the

order of 100 to 300 ms.

• Put into operation a priority queueing rule.

• Identify the links with the highest use and the slowest traffic. Estimate the link

delay of these links using Traceroute. Contact your service provider for help

with improving your QoS.

Reducing hop count

To reduce end-to-end delay can, reduce hop count, especially on hops that move

across WAN links. Some of the ways to reduce hop count include:

• Improve meshing. Add links to help improve meshing, adding a link from

average packet size in bytes

queuing time in ms = p X p X

(l-p)(link speed in kbit/s)

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Avaya BCM 2.0 IP Telephony Manual de usuario Pagina 32