Why Is Determining the Optimal MTU Size Important?
Determining the optimal MTU size is an important step in optimizing your network’s performance. The right MTU can provide several significant benefits, including:
Increase Internet Speed
An MTU that is too small will cause the data packet to be fragmented frequently. The process of fragmenting and reassembling packages takes additional time, which can slow down data transfer. With an optimal MTU, fragmentation can be minimized, so data can be transmitted faster.
Larger data packets (with higher MTUs) contain less overhead (additional information in the packet header). This means more data can be delivered in a single packet, making bandwidth usage more efficient.
Reduce Latency and Lost Packets
As mentioned earlier, fragmentation can increase latency. With an optimal MTU, latency can be suppressed, resulting in better network responsiveness. This is especially important for latency-sensitive applications, such as online gaming, video calls, and streaming.
Fragmentation can increase the risk of packets being lost in transit. Lost packages must be resented, which can cause delays and decreased performance. The right MTU can reduce the risk of packet loss.
Network Security
Some types of network attacks take advantage of fragmentation to hide malicious traffic. By setting the MTU correctly, you can prevent this kind of attack.
A stable network is a secure network. Optimal MTU can improve network stability, thereby reducing the risk of interference that attackers can take advantage of.
Other Factors to Consider
- Connection Type: The type of internet connection you use (DSL, cable, fiber optic) can affect the optimal MTU that can be used.
- Network Devices: Routers, switches, and other network devices have a maximum MTU supported. The MTU you set must not exceed the maximum value supported by the device.
- Network Protocols: Some network protocols have specific MTU requirements.
How to Determine the Optimal MTU:
- Ping with Don’t Fragment Options: You can use the ping command with the “-f” (don’t fragment) to find out the maximum MTU supported by your network path.
- Use Specialized Tools: Several specialized tools can be used to measure MTU, such as PathPing on Windows or traceroute on Linux.
- Consult your ISP: You can also consult your internet service provider for recommendations regarding the optimal MTU.
Steps to Determine the Optimal MTU Size
Preparation
Before conducting the MTU test, several equipment and preparations need to be done:
- Stable Internet Connection: Make sure your internet connection is stable and there are no interruptions.
- Computer Device: Prepare the computer or laptop that will be used to perform the MTU test.
- Access to the Router: Make sure you have access to the router’s settings, either through the web interface or the router manager app.
- Network Test Tool: You will need a network tool or utility, such as Command Prompt on Windows, Terminal on macOS, or Terminal on Linux.
Method Ping Test
The steps to perform the Ping Test to determine the optimal MTU size are as follows:
- Open Command Prompt or Terminal:
- Windows: Press Win + R, type cmd, and then press Enter.
- macOS and Linux: Open Terminal from the app or use the shortcut Ctrl+Alt+T (Linux).
- Type Command Ping: Use the ping command with the options -f (set the Don’t Fragment bit) and -l (specify the packet size) to send a data packet of a specific size without fragmentation. Start with a packet size of 1472 bytes (since the MTU size of 1500 bytes includes a 28-byte IP header).
ping [ip_address] -f -l 1472
- Reduce Package Size: If you receive the message “Packet needs to be fragmented but DF set”, reduce the package size by 10 bytes and repeat the command.
ping [ip_address] -f -l 1462
- Find Maximum Size Not Fragmented: Repeat step 3 until you find the maximum size that does not generate an error message. Add 28 bytes to determine the optimal MTU size.
ping [ip_address] -f -l [largest_size]
Practical Examples
- Windows:
ping google.com -f -l 1472
- macOS:
ping -D -s 1472 google.com
- Linux:
ping -M do -s 1472 google.com