ERR_CONNECTION_RESET – wrong MTU maybe the culprit

Today for the first time I saw ERR_CONNECTION_RESET error on Chrome. Chrome gave me: 

“Error 101 (net::ERR_CONNECTION_RESET): The connection was reset.”

This problem appeared when accessing a few website, one being my own website and other being gmail. Some other site loading has being rough too. While Firefox and IE9 were able to let me at least visit the site, Login didn’t work on them. And Since this was first time encountering this problem, I was confused – What is this and why now?

While searching for solution I came across one particular solution which helped me. I have given a source link at bottom of the post. Lets me summarize the problem. The culprit is wrong MTU value. This is not the first time I have heard of MTU, if I remember correctly I have used some utility to optimize my Internet and it set MTU values for best results. This was long time ago and doesn’t even apply to my current computer and Laptop.

You must be thinking what is MTU?

MTU – Maximum Transmission Unit of a communications protocol of a layer is the size (in bytes) of the largest protocol data unit that the layer can pass onwards. MTU parameters usually appear in association with a communications interface (NIC, serial port, etc.). Standards (Ethernet, for example) can fix the size of an MTU; or systems (such as point-to-point serial links) may decide MTU at connect time.

A larger MTU brings greater efficiency because each network packet carries more user data while protocol overheads, such as headers or underlying per-packet delays, remain fixed; the resulting higher efficiency means an improvement in bulk protocol throughput. A larger MTU also means processing of fewer packets for the same amount of data. In some systems, per-packet-processing can be a critical performance limitation.

How MTU is the Culprit?

Now, according to author, there are ways to test if in fact MTU is problem. I did try the test once, it is simple ping test, so I did it once only. I arrived at a conclusion that indeed MTU value needs to be changed. So what was happening is that due to some unknown reason high amount of bytes (more than 1408) were not been able to be transferred through Ethernet. Hence I lowered the MTU value from the default 1500 to 1408.

If you are facing similar problem and indeed MTU is the problem then check our Tutorial on How to change MTU Value.

Helpful Soucre: Error 101 (net::ERR_CONNECTION_RESET): The connection was reset