CenturyLink Bandwidth Speed Test Frequently Asked Questions

• Q:  What is a speed test?
  A speed test attempts to measure the maximum bandwidth -- or how fast your computer can talk to a server -- by downloading and uploading sample files, then measuring how much traffic passed during that period of time.
• Q:  What are Bits vs. Bytes?
  High-speed Internet lines are measured in bits per second. Most computer software applications measure speed in bytes per second.
• Q:  Are all speed tests (and speed test servers) the same?
  No. In order to test your high-speed Internet line and prove what it is capable of, it is best to test from the closest server to you. All bandwidth calculations and TCP settings (language your computer uses with other computers) on your computer and Web servers are based on latency, so the farther away the server is from your location the less chance you will get maximum performance. CenturyLink® servers have been optimized for CenturyLink high-speed Internet and placed in strategic locations for our customers.
• Q:  How can my computer or local network affect my high-speed Internet performance?
  When measuring performance, it is important to shutdown any unnecessary applications when conducting tests. In some cases, your firewall, antivirus, Wi-Fi connection, Ethernet cabling, and additional hubs/routers/switches can cause a decrease in performance. In order to eliminate potential issues, please try testing with your computer directly connected to your high-speed Internet modem. Make sure to remove any additional computers connected to your network, if you have a multi-port modem. Speed tests run over a Wi-Fi connection are not recommended.
• Q:  Why do different computers get different results?
  Computer operating systems, software installed, processor speed, memory, and network interface types can cause different speed test results.
• Q:  What speed should I get?
  With your high-speed Internet connection, the best speed your computer can theoretically measure is about 85% of your trained speed. That's because of the amount of overhead -- ATM, IP and PPP technologies -- that are required to pass your traffic. Keep in mind your modem is actually passing data at your full trained rate but some of the data is being stripped off.
• Q:  What is overhead?
  High-speed Internet rides over ATM and Ethernet transport. Your high-speed Internet modem establishes a session to CenturyLink and is terminated via a PPP session on our CenturyLink router; the session can either be PPPoA or PPPoE. Once the session is terminated it uses the IP protocol to pass data. In general depending on the transport type (ATM or Ethernet) and session type (PPPoA or PPPoE) there will be approximately 11%-15% of transport and protocol overhead.
• Q:  How many times should I run the test?
  The best way to conduct any test, to establish a standard or trend, is to run itseveral times at different times of the day. It should be sufficient to run the tests three or four different times.
• Q:  Why do my test results vary?
  All of the devices between your computer and the server can play a role in this. Each computer, switch, router, and server in the path can affect your results. Since your computer and the network are constantly changing your results may be impacted.
• Q:  What might I do to improve my test results?
  Here are a handful of helpful tips for troubleshooting bandwidth issues:
  1. Remove any unnecessary devices such as routers, switches, hubs, Wi-Fi devices and hook one computer directly to your high-speed Internet modem via an Ethernet cable or USB to conduct tests.
  2. If possible, try running the test from different computers to eliminate a PC configuration problem.
  3. If using Windows operating system check the task manager, if using a Mac check the activity monitor, for your computers statistics such as applications running, CPU load and memory. Close any unnecessary applications and or try and figure out why the CPU or memory is being highly utilized if applicable.
  4. Verify your computer TCP settings are optimal. You can see many of the configuration settings by going to a third-party website http://speedguide.net/analyzer.php.
  There is also freeware (software provided at no charge) that will change your default TCP settings to maximize the receive window. CenturyLink cannot accept any responsibility for your use of this third-party software. Note: Does not work with Vista operating system. http://www.speedguide.net/downloads.php
  5. Check your high-speed Internet modem statistics to see if your high-speed Internet line is taking errors. In the event this happens, make sure you have filters installed properly to every phone line except the high-speed Internet modem.
  6. If you are still having issues contact CenturyLink technical support.