DIA齊(qi)业專(zhuan)線(xiàn)上网：即IP城(cheng)域(yu)网（MAN，Metropolitan Area Network）指覆蓋(gai)城(cheng)市(shi)范围、爲(wei)城(cheng)市(shi)里各类用(yong)戶(hu)提供宽带 （通(tong)常2Mb/s以(yi)上）接入的(de)數(shu)字通(tong)信(xin)网络，IP城(cheng)域(yu)网采用(yong)光纤作(zuò)爲(wei)主(zhu)要的(de)傳(chuan)輸(shu)媒介来实現(xian)數(shu)据傳(chuan)輸(shu)...