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| 1.1 |  | Network Baselining |
| 1.1.1 |  | Network baselining overview |

When networks are first designed and installed, user requirements are gathered, analyzed, and translated into a network topology that satisfies the user requirements. The user requirements may be further extended into network performance goals such as bandwidth utilization, network latency and delay, and collision and error thresholds. In order to validate and document that the goals were achieved, specialized network monitoring and data collection is required. The process of network monitoring and collecting data is called baselining. The interpretation of the collected data is called baseline, or performance, analysis.

Baselining allows discovery of the true performance and operation of the network in terms of the policies that have been defined. Performance trends and faults may be identified by comparing future performance metrics to the baseline metrics.

After identifying data of interest for a policy, baselining allows a snapshot of the current state of variables throughout the network. Establishing a baseline for a network provides answers to the following questions:

- How does the network perform day to day?
- Where are the under-utilized and over-utilized areas?
- Where are the most errors occurring?
- What thresholds should be set for the devices that need to be monitored?
- Can the network deliver the identified policies?

The purpose of conducting a network baseline is to measure the initial performance and availability of critical network devices and links in order to compare them to future performance. The baseline allows a network administrator to determine the difference between abnormal behavior and proper network performance. It also provides insight into whether the current network design can deliver the required policies.

The task of baselining can best be accomplished in large, complex networks, using sophisticated network management software with integrated remote monitoring network devices. In simpler networks, these data collection tasks may require a combination of hand collection of data, augmented with simple network protocol instectors like Fluke Protocol Inspector or other shareware utilities that can be downloaded from the Internet at sites such as http://www.statscout.com. Selected examples of tools that may be used for baselining are discussed in Module 2, “Troubleshooting Methodologies and Tools” .

The collected data will reveal the true nature of congestion or potential congestion in a network. It may also reveal areas in the network that are underutilized. Analysis after an initial baseline tends to reveal hidden problems and quite often can lead to network redesign efforts based on quality and capacity observations. Another reason for conducting a baseline is that no two networks operate or behave the same way.

Without a baseline, no standard exists to measure the optimum nature of network traffic and congestion levels. Establishing an initial baseline or conducting a performance monitoring analysis, by collecting current data and comparing it to the baseline, require sufficient time to accurately reflect network performance. Network management software or protocol inspectors and sniffers may run continuously over the course of the data collection process. Hand collection by way of show commands on individual network devices is extremely time consuming and should be limited to mission critical network devices.

The following sections describe the general methodology for defining, collecting, and reporting a network performance baseline. This entails the collection of key performance data from the ports and devices considered to be mission critical. The baseline is a vital preliminary step in determining the personality of the network. It also simplifies the setting of effective thresholds.

The following are steps to building a baseline:

- Planning for the first baseline
- Identifying devices and ports of interest
- Determining the duration of the baseline