Performance Testing

This is a high level generic document outlining some common information about network performance issues and how to troubleshoot them.

What is network performance?

A measurement of how well a network is functioning.

How do you measure network performance?

By simulating network traffic using networking tools and analyzing the data. Multiple tests should be run at various times to benchmark your network.

What are some standard networking tools?

CenturyLink cannot accept any responsibility for your use of third-party software.

• Ping
• Traceroute
• Logs & Graphs
• Speedtest Applications (example CenturyLink Speedtest)
• Iperf (for Windows) & Jperf (for Windows)
• Jitter
• Throughput Calculator
• Speed Guide Tools
• Wireshark

What are typical performance issues?

• Loss
• Delay
• Congestion
• Out of order data

What causes performance issues?

Potentially any device (router, switch, firewall, server, computer) or link (ethernet, coax, copper, fiber) within a network.

When you identify a performance issue what should I look for?

1. Verify if there were any changes in the network around the time the issue started.
2. Check router or switch logs, many times there can be critical log messages that may help identify potential issues.
3. Check all routers, switches, devices & interfaces in the path for utilization and or errors. Specifically CPU load, interface errors, CRC errors, packets per second, and bits per second.

I have looked at everything in my network but can’t find anything, now what?

Determining you have performance issues is the first step; figuring out what is causing it can be difficult.

Using networking tools and ISOLATION is the key to finding network performance issues.

Eliminate and segment the network then retest using networking tools to try and isolate the issue.

Some common questions that may be asked by a support person:

• What are your network symptoms (examples: packet loss, delay, congestion)?
• What is the frequency of the event (all the time, common times, intermittent)?
• Can you replicate the problem?
• Does the problem happen only when going to a specific destination or everywhere?
• Have you verified everything under the section “When you identify a performance issue what should I look for”?
• Have you isolated your network, if so please explain what has been isolated and what tools were used?

What information will CenturyLink look at to help verify their portion of the network?

The most common things technicians will look at when a customer has a performance issue are:

1. Existing tickets or outages that could be causing the problem.

2. CenturyLink's equipment; specifically the customer facing port via current and historical graphs. Also logging into the device (router or switch) and verifying logs, interface statistics, cpu load, and additional information.

3. The path and all the elements between the source and destination of the problem.

What if no problems are found?

CenturyLink has performance servers placed strategically within its network that allow technicians to work with customers who wish to run Iperf or Jperf tests to help isolate performance issues.

It may be necessary for customers to do packet captures using Wireshark to analyze the data.