CrossNodes Briefing: Network Diagnostic Tools

Maintaining a network requires tools and knowledge. Problems arise that must be diagnosed. Bottlenecks slow traffic. Bridges and routers begin sending bad packets of information. Without diagnostic tools, network technicians can only guess at the answers. They need tools to look at the traffic, determine performance, and isolate problems. These types of diagnostic tools exist, but the range of capabilities from powerful, multifunctional analyzers to line testers can be confusing.

In general, diagnostic devices allow network technicians to look inside the network and watch how the network handles data. Some offer remote capabilities that allow technicians to access the read outs from any workstations. Others are self-contained, including hand-held units. The tools help isolate inconsistencies across the network and allow them to make the adjustments and maximize network throughput. Diagnostic tools can be software or hardware based, and some support intelligent devices, while others do not.

On the low end, the tools simply monitor line connections. Top-of-the-line equipment can analyze traffic and routing schemes and provide the technician with sophisticated tools to diagnose and predict problems. The functionality of diagnostic equipment can include:

  • Transmission rates:   By tracking the transfer rates of packets and frames, technicians can better understand where a network will slow under high traffic volume.
  • Utilization:   Allows technicians to determine if the network is operating a maximum capacity, indicating an upgrade, or whether there is sufficient bandwidth and processing power to expand the network.
  • Errors:   Permits technicians to determine error rates and isolate devices that are causing problems.
  • Line Loading/traffic generation:   Tests network throughput and the quality of transmission by creating artificial traffic and line conditions.
  • Address resolution:   Ensures that all addresses are unique, which in turn helps the network function more efficiently.
  • Quality of Service (QoS) audit:   Verifies that the throughput and quality of transmission signals meet the guarantees given by outside line providers.

Some vendors include additional functionality and usability features in their diagnostic tools. Network mapping, for example, can identify all connected equipment and help determine if the network requires additional switching or configuration changes to maintain its efficiency. Diagnostic equipment also can isolate problems, permitting the technician to respond to outages or slowdowns quickly. Several diagnostic tools are capable of sending alarms to technicians using e-mail and paging, and this helps speed response times when error conditions arise.

Diagnostic tools also exist for web site providers. It is important to know how a web site appears to perform when a user accesses it. A slow web site creates a negative impression, and if it is an e-commerce site, this can lower revenues. Several diagnostic tools provide analysis of web site performance, including measuring the response time of the web site, analyzing the site for broken links, identifying HTTP traffic patterns, and generating trace logs to determine how users move around the site.

Finding the Right Tool
Like all purchases, the selection of diagnostic tools starts with an assessment of needs. If technicians only need to troubleshoot occasional bad connections on a simple LAN configuration, digital line testers will suffice. However, complex networks will require continuous monitoring and tools that are more powerful. Of course, the price of the test equipment rises as capability increases.

Diagnostic tools generally support very specific tests. They offer one or more line level functions that look at the signal as it crosses the network connections, including:

  • Digital line tests:   Allow technicians to verify that links operate at the correct speed without excessive errors.
  • Protocol analysis:   Identifies the format of the data that passes across the network and enables technicians to determine if changes in packet sizes and address routing can increase the network’s efficiency.
  • Data line monitoring:   Collects detailed information about the traffic passing across a specific link, allowing technicians to create an efficient network by upgrading links.
  • Protocol emulation:   Generates traffic using several protocols allowing technicians to model network performance using different protocols.
  • BERT/BLERT tests:   Create traffic and measure the number of errors that occur on end-to-end transmissions.
  • RMON probing:   Offers access to remote devices. This is very useful for distributed networks.

High-end diagnostic tools integrate these features and add others. With more advanced equipment, Technicians can view individual packets and, when necessary, repair bad packets. Further, the tools allow technicians to view the various control layers of the network to gain a better understanding of how the network functions and provide fixes to problems or alternative solutions that will improve network performance.

As networks expand and incorporate Wide Area Network (WAN) connection in the LAN, the testing tools change. For companies operating a dispersed network, technicians will need support for multiple protocols and traffic types as well as physical connections. Some vendors specify the types of equipment that their diagnostic tools support, so technicians must try to find the equipment that will recognize as many bridges, switches, and routers as possible if they have products from multiple vendors.

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