Network performance utilities – Nortel Networks NN43001-563 User Manual

Page 72

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System description

Packet delay

Packet delay is the time between when a packet is sent and when it is
received. The total packet delay time consists of fixed and variable delay.
Variable delay is more manageable than fixed delay, as fixed delay is
dependent on network technology. Variable delay is caused by the network
routing of packets. The IP Trunk 3.01 (and later) node must be as close
as possible to the network backbone (WAN) with a minimum number of
hops, in order to minimize packet delay and increase voice quality. ITG
provides echo cancellation, so that a one-way delay up to 200 milliseconds
is acceptable. For more information about Echo Cancellation, see

"Echo

cancellation" (page 67)

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Delay variation (jitter)

The amount of variation in packet delay is referred to as delay variation or
jitter. Jitter affects the ability of the receiving IP trunk card to assemble
voice packets into a continuous stream when the packets are received at
irregular intervals.

Latency

Latency is the amount of time it takes for a discrete event to occur.

Bandwidth

Bandwidth is a measure of information carrying capacity available for a
transmission medium. The greater the bandwidth the more information
that can be sent in a given amount of time. Bandwidth is expressed in bits
per second (bps).

Network performance utilities

Two common network performance utilities, Packet InterNet Groper (PING)
and Traceroute, are described in this section. Other utilities can be used to
gather information about IP Trunk 3.01 (and later) network performance.

These descriptions are for reference purposes only. Traceroute is not part of
the IP Trunk 3.01 (and later) product.

Because network conditions can vary over time, collect performance data
over a period of at least four hours. Use performance utilities to measure
network performance from each IP Trunk 3.01 (and later) node to every
other IP Trunk 3.01 (and later) node in the network.

Packet InterNet Groper (PING)

Packet InterNet Groper (PING) sends an Internet Control Message Protocol
(ICMP) echo request message to a host, expecting an ICMP echo reply.
This allows the measurement of the round-trip time to a selected host. By
sending repeated ICMP echo request messages, the percentage of packet
loss for a route can be measured.

Nortel Communication Server 1000

IP Trunk Fundamentals

NN43001-563

01.01

Standard

Release 5.0

30 May 2007

Copyright © 2007, Nortel Networks

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