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Understanding the network.pdf - Back to Home

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samples will tell you what you need <strong>to</strong> know. If it's a 24-7 environment, <strong>the</strong><br />

once-an-hour method is for you.<br />

Several data measurements are used <strong>to</strong> determine <strong>the</strong> <strong>network</strong> performance<br />

baseline. These measurements can be categorized in<strong>to</strong> four basic data categories,<br />

discussed in <strong>the</strong> sections that follow.<br />

WAN Link, LAN Segment, and Node Layer 2<br />

Bandwidth Utilization<br />

Utilization is a measurement of <strong>the</strong> percentage of time <strong>the</strong> transmission medium is<br />

in an active state (transmitting frames, for example). Two types of utilization<br />

measurements exist: Layer 2 utilization, expressed in Frames Per Second (FPS) and<br />

Layer 3 utilization, expressed in Packets Per Second (PPS). Utilization is measured<br />

by calculating <strong>the</strong> number of frames/packets transmitted over a one-second<br />

interval.<br />

NOTE<br />

The terms "packet" and "frame" are often used interchangeably. Frame refers <strong>to</strong><br />

Layer 2 transmission messages, and packet refers <strong>to</strong> a Layer 3 datagram; packets<br />

are transported in frames.<br />

When looking at <strong>network</strong> performance in terms of utilization, three components<br />

need <strong>to</strong> be examined: composite bandwidth utilization, broadcast bandwidth<br />

utilization, and composite bandwidth utilization distribution. These three<br />

components determine if <strong>the</strong> <strong>network</strong> is performing up <strong>to</strong> its expectation.<br />

The average utilization is a measurement of <strong>the</strong> <strong>network</strong> throughput based on<br />

average packet size and frame rate. The <strong>network</strong> segments average utilization<br />

measurement is calculated by recording <strong>the</strong> <strong>network</strong> segments traffic throughput<br />

(consisting of both, good and bad frames) over a specified period of time (usually a<br />

30- <strong>to</strong> 60-minute interval). The average utilization measurement is a single value<br />

determined by pro<strong>to</strong>col analyzer or <strong>network</strong> moni<strong>to</strong>ring <strong>to</strong>ol used <strong>to</strong> collect <strong>the</strong><br />

traffic sample. The analyzer/moni<strong>to</strong>r determines <strong>the</strong> average utilization<br />

measurement, by calculating <strong>the</strong> mean average throughput of sample data<br />

collected.<br />

The peak and low utilization measurements are determined using <strong>the</strong> same <strong>network</strong><br />

sample data used <strong>to</strong> determine <strong>the</strong> <strong>network</strong> average utilization. However, <strong>the</strong> peak<br />

and low measurements are concerned with utilization in terms of <strong>network</strong>

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