Routers with multiple user increasing latency by request is normal?

Question

I guess my modem have a problem with multiples users sending packages simultaneously, in the past I shared my internet connection with others 4 devices (computers and smartphones) and I played online games (dota, league of legends, counter strike) and my ping is normal was 25~40 ms. But now, I share my connection with others 4 devices (one notebook, and 2 smartphones and 1 tablet) and my ping is horrible! Sometimes jump from 32ms to 700ms or more, when only my notebook is connected there is no lags, my latency do not have spikes, but if some other device connect together with me the ping jump to 700ms and is impossible play any online game, navigation is normal.

So, my question is : There is possible that my modem can not support with more than one device with a good latency or is normal the latency up to 700ms ? I did a test on cmd, I did my pc ping to my IP modem"forever" and while try open sites, download files in my smartphone, I notice that de latency grows up from 2ms to 57ms/130ms/455ms. Is normal?

I don't have a dedicated router, I just use a modem that have a router wifi function imbedded. To Buy a router dedicated will improve the connection?

Look the IMAGE, when I open websites or I try use speedtest in my smartphone the ping have several spikes

I had the same problem using cable or wifi.

PS: Sorry about my english

Answer 1

You have a dumb router ( or actually, it could be your isp ). The problem is known as "buffer bloat". Basically it means the router has gobs of ram and is happy to use it all to queue up packets waiting to be sent. The more packets you queue up, the longer the queue gets, the more time it takes for a packet to make it through the queue. This is compounded by the way that TCP operates when it sees latency. TCP assumes that latency is caused by the link itself, rather than congestion, for instance, a satellite link has high latency because it takes time for the signal to travel thousands of miles to orbit and back to earth. TCP responds by sending more packets before waiting for an acknowledgement, which fills up the router buffers more, which makes the latency worse, and you have a positive feedback loop.

This problem was recognized years ago and modern routers limit the depth of their queues and just start discarding packets rather than letting the latency get out of control. If the problem is your router, then buying a new one may help. If the problem is on your ISP's end though, you are out of luck. You can tell the difference by experimenting and see which type of traffic causes the latency: uploading, or downloading. If it's downloading, then it's on your ISP's end.