Nortel Networks NN43001-504 manual Assessment using NetIQ Vivinet Assessor

Network management 49

Both location-solution types use a form of triangulation to compute the location of the device. Depending on the power level of the AP, it can sometimes hear devices that it cannot transmit to. These factors combined create the following two scenarios:

•It is difficult to calibrate network-based solutions by using a laptop running the site survey, because APs can sometimes hear clients that cannot hear the AP. If AP transmission power levels are not at a maximum, they can hear clients over a greater distance than their own transmissions can travel. This scenario can cause the site survey application to underestimate the number of APs that can participate in triangulation.

•Client-based solutions cannot triangulate APs that are not detectable because their power is lower. But the site survey application can accurately reflect the number of APs that can be used for triangulation.

Assessment using NetIQ Vivinet Assessor

The Network Health Check is probably the most critical step toward ensuring a smooth rollout for any VoIP deployment. This statement applies even more so to VoWLAN, because a WLAN is a more challenging QoS environment than modern wired networks.

The NetIQ Vivinet Assessor 3.0 or later is the tool of choice for network health checking. (Previously NetIQ Chariot, now an Ixia product, was recommended for network health checking.) This product uses a laptop (for WLAN testing for WLAN mobility) as a voice-traffic generation and analysis tool. You can configure several nodes in various parts of the network, to simulate calls to and from those areas. Each node simulates call volumes through traffic generation so that you can stress-test access links, backbones, and WAN links as necessary. You can also configure codecs, packetization rates, and other factors to closely mimic the future VoIP environment.

Vivinet Assessor performs a comprehensive analysis of the simulated traffic, including reports on delay, jitter, and packet loss. The R values or Mean Opinion Score (MOS) are reported for these simulated traffic loads to provide a baseline for performance expectations. These analyses are also used for capacity planning because they show the capacity at which the Quality of Experience (QoE) ratings start to fall. More importantly, the process of analyzing the network reveals many latent network problems that can otherwise remain undetected until deployment.

For example, duplex mismatches can exist in various locations of the network, and data applications, being very tolerant to packet loss, typically do not reveal the problem unless it is severe. The issue is immediately

Nortel Communication Server 1000

WLAN IP Telephony Installation and Commissioning

NN43001-504 01.02 Standard

Release 5.0 15 June 2007

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