How To Enable Flow Control on a Network Adapter?

Welcome to the Network Engineering tutorial section by CoreNetworkZ Tech Solutions. Today, I will explain the concept of flow control for Network Interfaces.

Many students (who are new to Network Engineering) asked me this question. They are not alone. A few of our readers also asked the same question. So, let me explain what network flow control is in this section.

Network flow control is a technique that regulates the number of frames transmitted between two network interfaces to avoid data conjunction. This technique is helpful when one Network Interface is faster than the other. Since you have learned the concept, let us go to the next section.

I write this section based on my personal experience as a Network Engineer. You can also consider it a supporting article for my other network troubleshooting guides published by CoreNetworkZ Tech Solutions.

Consider a scenario where your computer is a part of a high-speed network. What will happen if your Network Adapter receives input frames more than it can handle ( without a flow control enabled option)?

The answer is simple. It will result in frame loss.

Do you know why? The sender is not getting information about the possible frame loss. So, it will not stop sending more frames.

With the flow control enabled option, your Network Adapter will send a pause frame that tells the sender (sender of frames to your NIC) to pause the transmission until its buffer is free.

So, if your NIC is slower (while connecting to a high-speed network), you may need to enable the Flow Control property to avoid packet loss. I believe you have understood the importance of this feature.

In this section, I will explain how to activate the Adapter flow control on a Windows computer.

1. Go to Network Connections Window

   We can access the Network Connections Window via two methods. The first method is via the Run command. The second method is the Windows GUI. I will explain both methods in this section.

   1. By Run Command
   • Click on Start
   • Type ncpa.cpl on Search and press the Enter key.
   2. By GUI
   • Click on Start
   • Go to Control Panel
   • Click on Network and sharing center
   • Click on Change Adapter Settings

   Now, you are in the Network Adapter window, where you can see all the NICs installed on your computer.

   

2. Right-click on the Local Area Connection, and click on the Properties option. You can see the screenshot of the right-click menu below.

   

3. Click the Configure button

   

   Now, you may receive one warning message, "You have made changes to the properties of this connection. If you proceed, your changes will be lost. Do you wish to proceed?".

   

   Click on the yes button to proceed.

4. Click the Advanced Tab

   

5. Select Flow Control from the list and choose Enable.

   

   After selecting the option, you should click OK. Now, the flow control property of the Ethernet adapter is enabled.

   If you want to change the link speed and duplex settings, select Speed and Duplex.

With these five steps, you can turn on or deactivate the Network Adapter flow control on a Windows device.

I saw comments from Stephen Curry and Chris Paul asking me to explain how to enable Network Interface flow control on a Linux device. I will answer their questions in this section.

You can perform it on an Ubuntu PC by following the steps below.

1. Open Terminal and type the following commands.

   sudo apt-get update

   sudo apt-get install ethtool

2. Type the following command to enable NIC flow control.

   sudo ethtool -A eth0 rx on tx on

3. Type the following command to disable NIC flow control on an Ubuntu PC.

   sudo ethtool -A eth0 rx off tx off

Richard Durrant asked me about the uses of this feature. He is a CCNA student and a regular reader of tutorials prepared by CoreNetworkZ Tech Solutions. So, let me answer his question in this section.

The primary use is to avoid frame conjunction at the slower NIC. It will prevent data loss and improve the communication between sender and receiver Network Interfaces.

1. https://www.juniper.net/documentation/us/en/software/junos/interfaces-ethernet/topics/topic-map/flow-control-ethernet-interfaces.html
2. https://community.cisco.com/t5/switching/flow-control/td-p/2463281