lag spikes, high ping on online games when another user is..

hi guys,

lately i have been going into some problems.

im using simple Queue and everything is working fine.

but for some reason, when a user is using all of his bandwidth on the network, such as downloading or browsing, other users on the same network witness some high pings , and lag spikes for few seconds especially on online games.

Here is what is happening exactly: when a user opens the Steam to load Dota 2, the user who is opening steam shows a red color on the queue, and other users on the network witness some high ping spikes for few seconds.

This shouldnt happen because im using queues.

can someone explain to me what is the problem?
im ready to give more info. thanks.