我公司上网是电信的ADSL ，带宽1M，以前一直都很正常，最近出现了严重的问题：访问外网非常慢，经常打不开，但是如果一旦连接成功那么在这个连.接上的流量就很正常了，所有的机器都是这样，但是如果下.班了，网络就正常了，我看了N.AT（AS3）的下转发列表，里面有大量的TCP连接没有成功，都是发送出去了SYN_SENT包而没有回应，就是TCP 3次.握手没有完成，为什么会这样呢.，请帮我看看，谢谢！.
下面是转发列表里的部分内容：
[roo.t@adsl net]# c.at ip_conntrack | grep 192.168.0.221 乙肝
tcp 6 103 SYN_SENT src=192.168.0.221 dst=61.152.242..202 sport.=2771 dport=80 [UNRE.PLIED] src=6.1.152.242.202 dst=58.33.152.186 sport=80 dport=2771 use=1 .
tcp 6 4.31999 ESTABLISHED src=192.168.0.221 .dst=192.168..0.1 sport=1719 dport=22 src=192.168.0.1 d.st=192.168.0.221 sport=22 dport=1719 use=1 建材
tcp 6 104 S.YN_SENT src=192.168.0.221 dst=207.46.78.10.9 sport=2784 dport=80 [UNREPLIED] src=207.46.78.109 dst=58.33.152.186 sport=80 dport=278.4 use=1 .( 游戏 )
tcp 6 104 SYN_SENT .src=192.168.0.221 dst=207.46.78.94 spo.rt=2778 dport=80 [UNR.EPLIED] src=207.46.78.94 dst=58.33.152.186 sport=80 dport=2778 u.se=1 [成人用品]
udp 17 145 sr.c=192.168.0.221 dst=219.133.41.28. sport=6009 dport=8000 src=219.133.41.28 dst=58..33.152.186 sport=800.0 dport=6009 [ASSURED] use=1 ( 游戏 )
tcp 6 431976 ESTABLIS.HED src=192.168.0.221 dst=.207.46.78.94 sport=2777 dpor.t=80 src=207.46.78.94 dst=58.33.152.186. sport=80 dport=2777 [ASSURED] use=1 虚拟主机
tcp . 6 118 SYN_SENT src=192.168.0.221 dst=207.46.78.109 sport=2798 dport=80 [UNREPLIED] src=207..4.6.78.109 dst=58.33.152.186 sport=80 dport=27.98 use=1 建材
tcp 6 68 TIME_WAIT. src=192.168.0.221 dst=64.233.167.111 sport=.2765 dport=995 src=64.233.167.11.1 dst=58.33.152..186 sport=995 dport=2765 [ASSURED] use=1 <性病>
tcp 6 431988 ESTABLISHED src=192.16.8.0.221 dst=219.133.4.8.103 sport=2238 dport=443 src=219.133.48.103 dst=58.33..152.186 sport=443 dport=2238 [ASSURED] us.e=1 ( 游戏 )
tcp . 6. 39 SYN_S.ENT src=192.168.0.221 dst=207.46.78.94 sport=2764 dport=80 [UNREPLIED] src=207.46.78.94 dst.=58.33.152.186 sport=80 dport=2764 use=1 [成人用品]
udp . 17 11 src=192.168.0.221 dst=20.2.96.209.133 sport=1031 dport=53 [UNREPLIED] src=202.96.209.133 dst=58..33.152.186 sport=5.3 dport=1031 use=1 (广告)
tcp 6 431984 ESTABLISHED src=192.168.0.221 dst=207.46.7.8.94 sport=2781 dport=80 src=207.46.78.94 dst=58.33.152.186 s.port=80 .dport=2781 [ASSURED.] use=1 --- 印刷
tcp 6 63 TIME_WAIT src=192.168.0.221 dst=61.172.19.8.143 sport=2766 dport=110 .src=61.172.198.143 dst=58.33.152.186 sport=110 dport=2766 [ASSURED] use=1.. <性病>
tcp 6. 431974 ESTABLISHED src=192.168.0.221 dst=207.46.78.94 sp.ort=2770 dport=80 src=.207.46.78.94 dst=58.33.152.186 sport=80. dport=2770 [ASSURED] use=1 域名
udp 17 20 src=192.168.0.221 dst=192.168.0.255 .sport=137 dport=137 [UNREPLIED] src=192.168.0..255 dst=19.2.168.0.2.21 sport=137 dport=137 use=1 .
tcp 6 0 TIME_WAIT src=192.168.0.221 dst=61.172.198.1.43 sport=2762 d.port=110 src=61.172.198.143 dst=58.33.152.186 sport=.110 d.port=2762 [ASSURED] use=1 女人
tcp . 6 104 SYN_SENT src=192.168.0.221 dst=2.07.46.78.109 sport=2779 .dport=80 [UNREPLIED] src=20.7.46.78.109 dst=58.33.152.186 sport=80 dport=2779 use=1 鲜花
tcp. 6. 118 SYN_SENT src=192.168.0.221 dst=207.46.7.8.109 sport=2800 dport=80 [UNREPLIED] src=207.46.78.109 dst=58.33.152.186 sport=80. dport=2800 use=1 服务器
udp 17 12 src=192.16.8.0.221 dst=202.96.209.133 sport=356.6 dport=53 [UNREPLIED] src=202.96.2.09.133 dst=58.33.152.186 sport=53 dport=3566 .use=1 域名
tcp 6 104 SYN_SENT src=192.168.0..2.21 dst.=.207.46.78.94 sport=2780 dport=80 [UNREPLIED] src=207.46.78.94 dst=58.33.152.186 sport=80 dport=2780 use=1 .
tcp 6 431976 ESTABLISH.ED src=192.168.0.221 dst=207.46.78.94 sport=2774 dport=80 src=207.46.78.94 dst=58.33.152.186 .sport=80 dport=.2774 [ASSURED]. use=1 电影
t.cp 6 118 TIME_WAIT src=192.168.0.221 dst=61.152.2.42.202 sport=2797 dport=80. src=61.152.242.202 dst=58..33.152.186 sport=80 dport=2797 [ASSURED] use=1 .
tcp 6 431998 ESTABLISHED src=192.168.0.221 dst=207..46.78.109 sport=2785 dport=80 src=207.46.7.8.109 dst=58.33.152.186 sport=80 dport.=2785 [ASS.URED] use=1 乙肝
tcp 6 431975 ESTABLISHED src=192.168.0.221 dst=207.46.78.94 sport=2768 dpor.t=80 src=207.46.78.94 dst=58.33.152.186 sport=80 dport=2768 [ASSURE.D]. use=1. 外汇
tcp 6 104 SYN_SENT src=192.168.0.221 dst=207.46.78..94 sport=2791 dport=80 [UNREPLIED] sr.c=207.46.78.94 dst=58.33.152.186 spo.rt=80 d.port=2791 use=1 .
udp 17 11 s.rc=192.168.0.221 dst=202.96.209.6 sport=1031 dport=53 [UNREPLIED] src=202..96.209.6 dst=58.33.152.186 spo.rt=53 dport=1031 use=1. [成人用品]
tc.p .6 428082 ESTABLISHED src=192.168.0.221. dst=207.46.2.31 sport=1724 dport=1863 src=207.46.2.31 dst=58.33.1.52.186 sport=1863 dport=1724 [ASSURED] use=1
t.cp . 6 104 SYN_SENT src=192.168.0..221. dst=207.46.78.94 sport=2789 dport=80 [UNREPLIED] src=207.46.78.94 dst=58.33.152.186 sport=80 dport=2789 use=1 .
tcp 6 104 SYN_SENT src=192.168.0.221 dst=207.46.78.94 sport=2793 dport=80 [UNREP.LIED] src=207.46.78.94 dst=58.33.152.186. .sport=80 dport=2793 us.e=1 乙肝
tcp 6 429620 ES.TABLISHED sr.c=19.2.168.0.221 dst=192.168.0.1 sport=2624 dport=3000 src=192.168.0.1 dst=192.168.0.221 spor.t=3000 dport=2624 [ASSURED] use=1 --- 印刷
tcp 6 431975 ESTABLISHED src=192.168.0.221 dst=207.46.78.94 sport=276.9 dport=80 src=207.46.78.94 dst=58.33.152.186 sport=8.0 dport=2769. [ASSURED.] use=1 ( 游戏 )
tcp 6 104 SYN_S.ENT src=192.1.68.0.221 dst=207.46.78.94 sport=2792 dport=80 [UNREP..LIED] src=207.46.78.94 dst=58.33.152.186 sport=80 dport=2792 use=1 电子
tcp 6 104 SYN_SENT src=192.168.0.221 d.st=207.46.78.94 s.port=2794 dport=80 [UNREPLIED] src=207.46.78.94 dst=58..33.152.186 sport=80 d.port=2794 use=1 .
tcp 6 116 TIME_WAIT src=192.168.0.22.1 ds.t=61.15.2.24.2.202 sport=2796 dport=80 src=61.152.242.202 dst=58.33.152.186 sport=80 dport=2796 [ASSURED] use=1 .
tcp 6 9 SYN_SENT src=192.168.0.221 dst=64.233.167.111 sp.ort=2763 dport=995 [UNREPLIED] src=64.233..167.111 dst=58.33.152.1.86 sport=995 dport=2763 .use=1 电子
t.cp 6 104 SYN_SENT src=192.168.0.221 dst=207.46.78.109 sport=2783 dport=80 [UNREPLIED] src=207.46.78.109 ds.t=58.33..1.52.186 sport=80 dport=2783 use=1 汽车
tcp 6 104 SYN_SENT src=192.168.0.221 dst.=207.46.78.109 sport=2787 dport.=80 [UNREPLIED] src=207.46.78.1.09 dst=58.33.152.186 sport=80 dport=278.7 use=1 外汇
tcp 6 104 SYN_SE.NT src=192.1.68.0.221 dst=207.46.78.94 spor.t=2790 dport=.80 [UNREPLIED] src=207.46.78.94 dst=58.33.152.186 sport=80 dport=2790 use=1 .
tcp 6 431999 ESTABLISHED src=192.168.0..221 dst=220.181.28.23.0 sport=1721 dport=443 src=220.181.28.230 dst.=58.33.152.186 sport=443 dport=1721 [ASSU.RED] use=1 乙肝
tcp . 6 118 SYN_SENT src=192.168..0..221 dst=207.46.78.109 sport=2799 dport=80 [UNREPLIED] src=207.46.78.109 dst=58.33.152.186 sport=80 dport.=2799 use=1 .
udp . 17 178 src=192.168.0.221 dst=202.96.209.133 sport=1025 dport=53 src=202.96.209.133 dst=58..33.152.1.86 sport=53. dport=1025 [ASSURED] use=1 电子
udp 17 12 src=192.168.0.221 dst=202.96.209.6 sport=3566 dport=53 [UNREPLIED] src=202.96.209.6 dst=58.33.15.2.186 sport=53 .dp.or.t=3566 use=1 .
udp 17 179 src=192.168.0.221 dst=202..96.209.6 sport=1025 dport=53 src=202.96.209.6 dst=58.33.152.186 sport=53 dpo..rt=1025 [ASS.URED] use=1 健康
tcp 6 431998 ESTABLISHED src=192.168.0.22.1 dst=207.46.78.109 sport=2776. dport=80 src=207.46.78.109 dst.=58.33.152.186 sport=80 dport=27.76 [ASSURED] use=1 学习
tcp 6 104 SYN_SENT src=192.168.0.221 dst=207.46.78.94 sport=2788 dport=8.0 [UNREPLI.ED] src=207.46.78.94 dst=5.8.33.152.186 sp.ort=80 dport=2788 use=1 <性病>
tcp 6 82 SYN_SENT src=192.168.0.221 dst=61.129.59.97 s.port=3527 dpor.t=5000 [UNREPLIED].. src=61.129.59.97 dst=58.33.152.186 sport=5000 dport=3527 use=1 女人
tcp 6 104 SYN_SENT src=192.168.0.221 dst=61.152.242.202 sport=2795 dport=80 [UNREPLIED] src=61.152.242.202 dst=58...33.1.52.186 sp.ort=80 dport=2795 use=1 乙肝
tc.p 6 431998 ES.TABLISHED src=192..168.0.221 dst=207.46.78.94 sport=2767 dport=80 src=207.46.78.94 dst=58.33.152.186 .sport=80 dport=2767 [ASSURED] use=1 .
tcp 6 431988 ESTABLISHED src=.192.168.0.221 dst=207.46.78.94 sport=2786 dport=.80 src=207.46.78.94. dst=58.33.152.186 sport=80 dpo.rt=2786 [ASSURED] use=1.
