Company network recently is very strange, open the web page is very slow, but software, download upload speed is normal, no problems with the DNS, network topology is not complicated, three telecom 100 m into a routing, routing has two switches, one is the master switch, the main switch cascade again in less than five switches, network, a total of about 70 people in one day, suddenly network card, is just a simple web page card, download to keep up with the normal speed, various software operation is also very normal, there is no card phenomenon, the most strange is that in a routing, before in routing is card before, just change the day of the new network is very good, the web is seconds, at that time I thought it was a router problem, but the next day and returned to the same... Later, which I think may be the machine in the attack, then the batch, finally ruled out to my own work on the machine, I a plug in cable machine, card, unplug, BuKa, then I put my heavy machine, so open a few hours later, began to card, I will be forced to, don't know the reason is, forgive I pretty good, only in the school set up the experience of the campus network, network maintenance is caught not, o great god answer