166 ITG engineering guidelinesIn subsequent design cycles, review and refine the QoS objective, basedon data collected from intranet QoS monitoring.Having decided on a set of QoS objectives, then determine the planningthreshold. The planning thresholds are based on the QoS objectives.These thresholds are used to trigger network implementation decisionswhen the prevailing QoS is within range of the targeted values. Thisgives time for implementation processes to follow through. The planningthresholds can be set 5% to 15% below the QoS objectives, depending onthe implementation lag time.Intranet QoS monitoringTo monitor one-way delay and packet loss statistics, install a delay and routemonitoring tool, such as PING and Traceroute on the TLAN subnet of eachIP Trunk 3.01 (and later) site. Each delay monitoring tool runs continuously,injecting probe packets to each ITG site about every minute. The amount ofload generated by this is not considered significant. At the end of the month,the hours with the highest one-way delay are noted; within those hours, thepacket loss and standard deviation statistics can be computed.See "Measure intranet QoS" (page 139) for information aboutimplementation of the PING hosts and the use of scripting.See "Obtain QoS measurement tools" (page 143) for information aboutwhere to obtain other more specialized delay and route monitoring tools.At the end of the month, analyze each site’s QoS information. Table 35"QoS monitoring" (page 166) provides a sample.Table 35QoS monitoringOne-way delayMean+σ (ms)Packet lossMean+σ (%) QoSSite pairLastperiodCurrentperiodLastperiodCurrentperiodLastperiodCurrentperiod ObjectiveSanta Clara/Richardson135 166 1 2 ExcellentGood ExcellentSanta Clara/Ottawa210 155 3 1 Good Excellent ExcellentDeclines in QoS can be observed through the comparison of QoS betweenthe last period and current period. If a route does not meet the QoSobjective, take immediate action to improve the route’s performance.Nortel Communication Server 1000IP Trunk FundamentalsNN43001-563 02.01 StandardRelease 5.5 21 December 2007Copyright © 2007, Nortel Networks.
