port 1/1 on the main campus, the port description on switch port 1/1 should be configured for the device (Router A) on the other end. The port description can then be used for adding clarity to the reports created from the baseline and performance monitoring.
Content 1.1 Network Baselining 1.1.4 Determining the duration of the baseline IIt is important that the length of time and the baseline information being gathered is sufficient to establish a typical picture of the network. This period should be at least seven days, in order to capture any daily or weekly trends. Weekly trends are just as important as daily or hourly trends. As an example, the engineers in Building 7 run a massive backup and software refresh, on Sundays at 2 A.M., on all 200 of their workstations. Because the backup server happens to be in Building 9, the push and backup saturate the corporate backbone. If the baseline was only performed from Monday through Friday, the saturation would be missed. A baseline needs to last no more than six weeks unless specific long-term trends need to be measured. Generally, a two-to-four-week baseline is adequate. Examples of baselines for CPU utilization over various intervals of time can be provided by the Multi Router Traffic Grapher (MRTG). This tool can be found at http://mrtg.hdl.com/mrtg.html. It is recommended that baseline measurement is not performed during times of unique traffic patterns. As an example, it would not be beneficial to perform the baseline over a holiday or during December if most of the company is on vacation. However long the initial baseline is chosen to last, plan to try different durations on subsequent baselines. This will allow discovery of the optimal analysis collection interval for the network.
Content 1.1 Network Baselining 1.1.5 Using the baseline data This is where all the attention to detail when collecting baseline information pays off. Policies have been defined including variables that measure the policies. Also, data has been collected from critical devices and connections for a period of time. By performing baseline tests on the network, it is possible to gain a better understanding of capacity and quality of service a network delivers. Now it is time to analyze the snapshot. The data can be used in the following ways to learn more about the network:
Content 1.1 Network Baselining 1.1.6 Identifying undesired network behavior An immediate benefit of baselining the network is the objective identification of undesired network behavior. By generating reports that identify the most utilized lines, areas of the network that are either experiencing problems or are prime candidates for failure, can be readily identified. At the same time, under-utilized areas of the network can be identified. Where redundancy is involved, it may be discovered that traffic is routing almost entirely over only one of the redundant connections. This may be undesirable because the bandwidth could be almost doubled in a properly configured network with load sharing. The identification of undesired network behavior may lead to a network redesign or a change in network policy. It may also be discovered that a device is configured incorrectly.
Content 1.1 Network Baselining 1.1.7 Identifying thresholds Efficient troubleshooting requires the setting of thresholds that reflect different levels of warning. Arriving at the appropriate thresholds for each of the network policies requires a baseline analysis. Initially, most network administrators consult the network device documentation or vendor technical support for a set of recommended or default thresholds. Generally, the answer received is “It depends – the thresholds vary according to individual networks.” Unfortunately, the nature of distributed networking forces the process of identifying or predicting a fault to be somewhat of an art form. Vendors who develop performance and fault tools may provide a set of defaults. Generally these default settings must be fine tuned to meet the needs of individual networks. The baseline analysis provides the data to study performance and fault patterns over a period of time. From this data, the appropriate thresholds can be determined, as it applies to network policies.
Content 1.1 Network Baselining 1.1.8 Predicting long-term performance and capacity trends As part of the planning cycle for the network, it is necessary to study network growth over a period of time. This study will provide understanding of how the network may continue to grow and provide data for obtaining funds for network expansion. As stated earlier, baseline studies should be scheduled on a regular basis. By comparing the data from each baseline, long-term growth trends can be isolated. These types of reports tend to be reported in terms of total bandwidth or total capacity for each link, for each device, and for the network as a whole. Network growth tends to occur in large bursts. Monitoring the hardware components is just one aspect of maintaining the performance of the network. The network administrator must also coordinate the use and upgrade of software applications, adjusting the network configuration, accordingly.
Content 1.1 Network Baselining 1.1.9 Verifying policies Determining whether a policy can be achieved in the network is a good use of a network baseline. By reporting the data in terms of the defined policies, it can be determined whether the network is adhering to or violating a policy, and to what degree adherence or violations are occurring. Figure displays a sample network policy that often specifies the consequences of policy violations. If the data reflects a policy violation, the issue must be resolved. Either the policy must be redefined, based on what the network currently delivers or a network redesign might be required. If the study reveals the need for a network redesign, data from the baseline analysis can be used objectively to justify the need for new equipment or service purchases.
Content 1.2 Network Configuration Documentation 1.2.1 Network configuration documentation overview When troubleshooting a network, a troubleshooter uses a baseline to efficiently diagnose and correct network problems. The baseline information for a network is captured in documentation such as network configuration tables and topology diagrams. This section discusses the creation of relevant and accurate network documentation as a troubleshooting tool for returning an underperforming, or failing, network back to an acceptable condition. The information contained in this section assumes a worst-case scenario where the network administrator is almost completely unfamiliar with a network and needs to create documentation from scratch. Useful network documentation will facilitate more effective troubleshooting, thereby saving time and effort. When the configuration of the network is failing or underperforming, a network configuration table will provide a saved configuration that should perform at an acceptable level. Network documentation will also eliminate the time-consuming and error-prone process of creating a network configuration from scratch. Network configuration documentation should include elements that provide a logical diagram of the network and detailed information about each component. The troubleshooter should find this information in a single location, either hard copy or on the network at a protected website. At a minimum, network documentation should include the following details: