我正在尝试与我的移动 ISP 建立 PPP 通信wvdial，但我总是得到调制解调器挂断信息。在我的中syslog我可以看到一些活动：
Oct 29 07:48:47 linuxbox kernel: [31222.852253] PPP generic driver version 2.4.2
Oct 29 07:48:47 linuxbox pppd[24590]: pppd 2.4.5 started by root, uid 0
Oct 29 07:48:47 linuxbox pppd[24590]: Using interface ppp0
Oct 29 07:48:47 linuxbox pppd[24590]: Connect: ppp0 <--> /dev/ttyUSB2
Oct 29 07:48:47 linuxbox pppd[24590]: CHAP authentication succeeded
Oct 29 07:48:47 linuxbox pppd[24590]: CHAP authentication succeeded
Oct 29 07:48:47 linuxbox kernel: [31223.014123] PPP BSD Compression module registered
Oct 29 07:48:47 linuxbox kernel: [31223.061839] PPP Deflate Compression module registered
Oct 29 07:48:47 linuxbox ifplugd(ppp0)[24612]: ifplugd 0.28 initializing.
Oct 29 07:48:47 linuxbox ifplugd(ppp0)[24612]: Using interface ppp0/00:00:00:00:00:00
Oct 29 07:48:47 linuxbox ifplugd(ppp0)[24612]: Using detection mode: IFF_RUNNING
Oct 29 07:48:47 linuxbox ifplugd(ppp0)[24612]: Initialization complete, link beat detected.
Oct 29 07:48:47 linuxbox ifplugd(ppp0)[24612]: Executing '/etc/ifplugd/ifplugd.action ppp0 up'.
Oct 29 07:48:47 linuxbox ifplugd(ppp0)[24612]: client: Ignoring unknown interface ppp0=ppp0.
Oct 29 07:48:47 linuxbox ifplugd(ppp0)[24612]: Program executed successfully.
Oct 29 07:49:08 linuxbox pppd[24590]: Modem hangup
Oct 29 07:49:08 linuxbox pppd[24590]: Connection terminated.
Oct 29 07:49:08 linuxbox avahi-daemon[1946]: Withdrawing workstation service for ppp0.
Oct 29 07:49:08 linuxbox pppd[24590]: Exit.
Oct 29 07:49:08 linuxbox ifplugd(ppp0)[24612]: Link beat lost.
Oct 29 07:49:08 linuxbox ifplugd(ppp0)[24612]: Exiting.
Oct 29 07:49:13 linuxbox pppd[24697]: pppd 2.4.5 started by root, uid 0
Oct 29 07:49:13 linuxbox pppd[24697]: Using interface ppp0
Oct 29 07:49:13 linuxbox pppd[24697]: Connect: ppp0 <--> /dev/ttyUSB2
Oct 29 07:49:14 linuxbox pppd[24697]: CHAP authentication succeeded
Oct 29 07:49:14 linuxbox pppd[24697]: CHAP authentication succeeded
Oct 29 07:49:14 linuxbox ifplugd(ppp0)[24711]: ifplugd 0.28 initializing.
Oct 29 07:49:14 linuxbox ifplugd(ppp0)[24711]: Using interface ppp0/00:00:00:00:00:00
Oct 29 07:49:14 linuxbox ifplugd(ppp0)[24711]: Using detection mode: IFF_RUNNING
Oct 29 07:49:14 linuxbox ifplugd(ppp0)[24711]: Initialization complete, link beat detected.
Oct 29 07:49:14 linuxbox ifplugd(ppp0)[24711]: Executing '/etc/ifplugd/ifplugd.action ppp0 up'.
Oct 29 07:49:14 linuxbox ifplugd(ppp0)[24711]: client: Ignoring unknown interface ppp0=ppp0.
Oct 29 07:49:14 linuxbox ifplugd(ppp0)[24711]: Program executed successfully.
Oct 29 07:49:35 linuxbox pppd[24697]: Modem hangup
Oct 29 07:49:35 linuxbox pppd[24697]: Connection terminated.
Oct 29 07:49:35 linuxbox avahi-daemon[1946]: Withdrawing workstation service for ppp0.
Oct 29 07:49:35 linuxbox pppd[24697]: Exit.
Oct 29 07:49:35 linuxbox ifplugd(ppp0)[24711]: Link beat lost.
Oct 29 07:49:36 linuxbox ifplugd(ppp0)[24711]: Exiting.
是什么导致了这个问题？