Some of you know that the router inside is actually a small computer. And like any computer, it has an operating system. Some vendors wrote their OS and some adopt existing ones. These days, most of them use the existing OS because write own OS is very hard and costs a lot of money. With existing OS vendors just need to write a network driver and some kind of user interface.

And even writing a network driver is not an easy task. You need developers who are experts in that field and thousands and thousands of hours to make sure that it is stable. As you can imagine, it cost a lot of money and the vendor cannot work for