White Paper: Network testing

Network testing provides a way to compile an inventory of a system’s set-up. Businesses stand to benefit from a thorough...

Network testing provides a way to compile an inventory of a system’s set-up. Businesses stand to benefit from a thorough understanding of their existing network’s configuration through efficient operations

In network testing, the focus is on four types of network nodes:

Top users

Top errored nodes

Interconnect equipment

Network peripherals.

Top users

In most networks, a small number of network nodes account for 80 per cent of the overall bandwidth utilised. The number of top users is dependent on the type of work performed by the network users. The remaining users account for around 20 per cent of the network activity. In a network of this sort, we are likely to focus on the top five network nodes.

Errors and nodes

We need to categorise nodes involved in creating or identifying network errors. Due to the multi-tiered structure of network communications, we are compelled to record network errors at various communication layers.

Interconnect equipment: network peripherals

Network peripherals fall into the following two categories: top listeners and top talkers. We should ensure that network peripherals have their workload properly distributed among network users. Improving network throughput and efficiency is the eventual goal of network testing. The packet is among the lowest common denominators in network communications.

Although plug-and-play networking allows the network manager to implement changes quickly, the price paid for quick implementation is usually a decrease in network efficiency.

On an Ethernet network, the maximum packet size is 1518 bytes. The bottom line is to determine the maximum data packet size for all network nodes.

Top users: protocols

We are interested in recording all network-layer, transport-layer, and application-layer information we can obtain.

Addressing

It is important to record all hardware, MAC, network, and symbolic addresses for each station. Note that today's networks are evolving into switched virtual networks. The direct impact on the network and network users is an increase in multicast and broadcast traffic.

Physical layer and MAC errors

In an Ethernet network, the collision rate can be considered as an indicator of the network utilisation.

Network layer errors

Protocols that use a network layer require a certain amount of management. They require the network manager to assign addresses and implement communication firewalls and network filters.

Regardless of the network layer protocol, pay special attention to:

Host/Station/Network Unreachable. This indicates that a node or piece of communication equipment or data link is not operating.

Time to Live Exceeded. This indicates that the network protocol has been unable to deliver a packet due to improper network design, incorrect network software setup, or network failure.

User interaction

When conducting a test, keep in mind the way the user will interact with the network. This way, faster network access can be achieved for the average user and costs can be easily rationalised.

Why network testing?

To bring the network under control, you must collect as much information about the network as possible. You can then revise the network testing to confirm the enhancement in network efficiency. You should test the network whenever you add users or change applications or communications equipment.

Focus on the node

By the time you begin to drill down to the individual network node, you have already developed a network testing philosophy that provides a clear understanding of the overall network. With the node-level testing, the goal is to investigate the specific users and peripherals involved in the network.

Who is out there?

In most networks, a small number of network nodes account for 80 per cent of the overall bandwidth utilised. In the first part of our node-specific baseline, we will determine how many top nodes to focus upon. In general, the top-nodes count will range between five and 20 heavy users. The number of top users is dependent on the type of work performed by the network users.

Top errored nodes

We need to categorise nodes involved in creating or identifying network errors. Due to the multi-tiered structure of network communications, we are compelled to record network errors at various communication layers. In the preceding article, we established that between 65 and 75 per cent of all network errors occur in the first three layers of the seven-layer OSI communication model. With this in mind, we should focus on recording errors at the Media Access Control (MAC) layer, Logical Link Control (LLC) layer, and the network layer.

Interconnect equipment

This category encompasses routers, bridges, switches and hubs. As we evaluate our top users, we are likely to find that these network-connectivity devices reside in our top user category.

One of the key requirements for our baseline is to take inventory of the equipment. Since the equipment is a critical component of the network, we should know as much about the types as possible.

Network peripherals

"The server is slow again!" If this is a frequently heard complaint, network testing is likely to provide the reasons why problems like this occur. Network peripherals fall into the following two categories: top listeners and top talkers. Devices such as servers, printers and facsimile machines are utilised by a multitude of different users. We should ensure that peripherals have their workload properly distributed among network users. Network efficiency can be improved by simply identifying and correcting load sharing and traffic flow between users and peripherals.

Overview

At the end of a comprehensive network testing, the reason you have undertaken this course of action should be obvious. Undoubtedly, you will have uncovered network skeletons in the wiring cupboard. Due to changes in network personnel and advances in technology and applications, networks tend to take on a life of their own. To bring the network under control, you must collect as much information about the network as possible.

Network testing is not a one-time event. After the initial session to set an acceptable minimum operating standard is complete, we can analyse the results and then apply our newfound knowledge to alter and enhance network efficiency. You can then revise the baseline to confirm the enhancement in network efficiency. Testing the network again whenever you add users or change applications or communications equipment is important, although baselining at regular intervals is also necessary.

The information that you gather and record will help maintain the network in a state of good health and keep your users happy.

Compiled by Paul Phillips

(c) Wandel and Goltermann

This was last published in March 2000

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