Addressing Error Messages
If you receive an error message like “Request timed out” or “Packet needs to be fragmented but DF set”:
- Reduce Package Size: Reduce the size of the package being tested until the error message disappears.
- Check Connection: Make sure there is no disruption to your internet connection.
Destination host unreachable: This means that the package cannot reach its destination. There may be a problem with the connection or the IP address you are using.
Packet too big: This means that the package size exceeds the MTU. Make a note of the size of the last successful packet before this message appears.
Fragmentation needed and DF set: This means that the package must be broken into fragments, but the don’t fragment (DF) option is enabled.
Testing and Setting MTU on the Router
After determining the optimal MTU size, the next step is to set up the MTU on your router. Here’s a general guide to some types of routers:
- Access Router Settings:
- Open a web browser and enter the IP address of the router (usually 192.168.1.1 or 192.168.0.1).
- Enter your username and password to access the settings interface.
- Navigate to MTU Settings:
- Look for the Network Settings, WAN Settings, or Advanced Settings options.
- Find the section to set up MTU.
- Set MTU Size:
- Enter the optimal MTU size that you have determined.
- Save the changes and reboot the router if needed.
Example Setup
- Netgear:
- Log in to the router’s web interface.
- Navigate to Advanced > Setup > WAN Setup.
- Set MTU Size and save the changes.
- TP-Link:
- Log in to the router’s web interface.
- Navigate to Network > WAN.
- Set MTU Size and save the changes.
By following the steps above, you can determine and set the optimal MTU size to ensure maximum network performance.
Case Studies
Case Study 1: User Experience That Successfully Improves Internet Speed by Setting MTU
A user, let’s call him Budi, experiences slow and often intermittent internet speeds, especially when streaming videos and playing online games. Budi uses a high-speed internet connection with a router that supports Ethernet networks.
Steps Taken
- Testing Internet Speed: Budi first tested internet speed using a speed testing site. The results showed a speed that was far below what it should be.
- Ping Test: Budi then conducts a Ping Test to determine the optimal MTU size. It uses the following command in the Command Prompt on a Windows computer:
ping google.com -f -l 1472
After several tests and packet size reduction, he found the maximum unfragmented packet size was 1464 bytes. By adding 28 bytes to the IP header, it determined that the optimal MTU size is 1492 bytes.
- Setting MTU on the Router: Budi then accesses the router settings and sets the MTU size to 1492 bytes in the WAN Settings section.
Result
After setting the optimal MTU size, Budi saw a significant increase in his internet speed. Video streaming runs smoothly without buffering, and the online gaming experience becomes more stable and responsive. The download and upload speed also increases according to the internet plan he uses.
Case Study 2: Cases of Failure Due to Suboptimal MTU Size and How to Overcome It
One user, let’s call him Ani, is having trouble with the VPN connection on his office network. When connected to a VPN, it often experiences long connection times and frequent disconnections. This problem has an impact on work productivity and access to company resources.
Problems Faced
- High Latency: Ani experiences high latency when connected to a VPN, which makes access to files and apps very slow.
- Packet Loss: There are significant indications of packet loss, which causes data to be frequently lost or corrupted during transmission.
Steps Taken
- Problem Identification: Ani consulted with the IT team in her office, who suspected the issue was related to suboptimal MTU sizing.
- Ping Test: The IT team performs a Ping Test to determine the optimal MTU size using the following command in Terminal on a macOS computer:
ping -D -s 1472 google.com
After several tests, they found that the maximum unfragmented packet size was 1432 bytes. By adding 28 bytes to the IP header, they determined that the optimal MTU size is 1460 bytes.
- Setting the MTU on the Router: The IT team then sets the MTU size to 1460 bytes on the office router and also sets it on the VPN configuration.
Result
After setting the optimal MTU size, the Ani VPN connection issue is resolved. Latency is significantly reduced, and there is no more significant packet loss. Access to files and apps through a VPN is faster and more stable, increasing Ani’s productivity at work.