How to Detect a Bottleneck

Detecting bottlenecking in your network requires a little foresight, some free tools and a little common sense. Before a bottleneck occurs, you need to know what you network looks like when it’s performing perfectly. Then you want to rule out possible PC issues. Finally, you can run the Traceroute diagnostic command to pinpoint where the bottleneck occurs.

Establish a Baseline Before a Bottleneck Test

Your internet service provider (ISP) provides an internet connection with a certain maximum bandwidth. Actual bandwidth can fluctuate based on a number of conditions. Periodically plug a computer directly into your internet modem as possible, and run a speed test. Numerous speed testing services are available online.

Run multiple tests back to back to ensure a single test wasn’t a fluke. Record or remember the upload and download speeds and the time of day. This helps you later ascertain that what you’re experiencing is a true bottleneck, despite not being a specific bottleneck test.

Test Your Devices

Before you begin complicated troubleshooting, try to replicate the PC bottlenecking issue using another device. Although this device can be any internet-capable device, try to use a computer that has capabilities similar to the computer you usually use. For example, if you have been having trouble with your desktop PC, a laptop would work better than a smartphone for testing. Use the same programs and attempt to access the same resources.

If the problem appears to affect both devices, then you know the issue isn't likely to be either of those devices. Run a speed test on both devices and compare them to your previously recorded performance benchmark.

Test Your Network

Determine whether the root of your bottleneck issue lies with the incoming internet connection or your network. Connect the cable from your internet modem directly into your computer and test the connection. If you make this direct internet connection and don't experience the same bottleneck issues as before, the issue lies with your own wired or wireless local-area network (LAN). Power down all of your computer devices one by one, checking the connection each time, in order to identify whether one of those devices is hogging your bandwidth.

If you don't discover the source of the problem this way, you may have a faulty switch, router or wiring. Professionals use a network analyzer to detect wiring problems. If you have a manageable switch, you can look at the debugging information to see if there are failures, or swap current networking equipment with comparable equipment to pinpoint problems with specific hardware.

Trace the Problem With Diagnostic Testing

You can also run a trace route command to find out if the router is causing the bottleneck, as suggested by Tech Republic. Access the command prompt by typing "cmd" (without quotes) into your search bar, and then type "tracert [destination IP]" (without quotes) to run the Traceroute command, where the destination IP is a specific IP address or website URL.

As packets move along the path from your computer to the destination IP, this diagnostic test asks every router it goes through to report back to your computer. Among this information is the amount of time it took for that device to respond. In a healthy network, devices respond in reasonable amounts of time. A router causing a bottleneck, however, will report a significant increase in time over the previous router.

If the problem router has the name of your ISP in it (such as "myISP.router32.backbone.net"), then the bottleneck likely resides with your ISP. If this is the case, note the results of the Traceroute before closing the command prompt window, and contact your ISP with this information.