ubuntu 8.10 alpha6 网络问题

[mybays]

dell inspiron 6400,网卡型号Broadcom Corporation BCM4401-B0 100Base-TX (rev 02)
安装 ubuntu 8.10 alpha6，升级到内核 2.6.27-4.6
问题：只要下载速度一变快，就有很大的可能断网，怀疑和b44的驱动有关，断网时的syslog如下：
Sep 26 18:11:19 spaceship kernel: [ 4412.996691] b44: eth0: powering down PHY
Sep 26 18:11:20 spaceship kernel: [ 4413.989105] b44: eth0: Link is down.
Sep 26 18:11:20 spaceship NetworkManager: <info> (eth0): carrier now OFF (device state 8)
Sep 26 18:11:20 spaceship NetworkManager: <info> (eth0): device state change: 8 -> 2
Sep 26 18:11:20 spaceship NetworkManager: <info> (eth0): deactivating device.
Sep 26 18:11:20 spaceship NetworkManager: <info> eth0: canceled DHCP transaction, dhcp client pid 25837
Sep 26 18:11:20 spaceship NetworkManager: <WARN> check_one_route(): (eth0) error -34 returned from rtnl_route_del(): Sucess
Sep 26 18:11:20 spaceship avahi-daemon[6076]: Withdrawing address record for 118.229.162.208 on eth0.
Sep 26 18:11:20 spaceship avahi-daemon[6076]: Leaving mDNS multicast group on interface eth0.IPv4 with address 118.229.162.208.
Sep 26 18:11:20 spaceship avahi-daemon[6076]: Interface eth0.IPv4 no longer relevant for mDNS.
Sep 26 18:11:22 spaceship kernel: [ 4415.989187] b44: eth0: Link is up at 100 Mbps, full duplex.
Sep 26 18:11:22 spaceship kernel: [ 4415.989197] b44: eth0: Flow control is off for TX and off for RX.
Sep 26 18:11:22 spaceship NetworkManager: <info> (eth0): carrier now ON (device state 2)
Sep 26 18:11:22 spaceship NetworkManager: <info> (eth0): device state change: 2 -> 3
Sep 26 18:11:22 spaceship NetworkManager: <info> Activation (eth0) starting connection 'Auto eth0'
Sep 26 18:11:22 spaceship NetworkManager: <info> (eth0): device state change: 3 -> 4
Sep 26 18:11:22 spaceship NetworkManager: <info> Activation (eth0) Stage 1 of 5 (Device Prepare) scheduled...
Sep 26 18:11:22 spaceship NetworkManager: <info> Activation (eth0) Stage 1 of 5 (Device Prepare) started...
Sep 26 18:11:22 spaceship NetworkManager: <info> Activation (eth0) Stage 2 of 5 (Device Configure) scheduled...
Sep 26 18:11:22 spaceship NetworkManager: <info> Activation (eth0) Stage 1 of 5 (Device Prepare) complete.
Sep 26 18:11:22 spaceship NetworkManager: <info> Activation (eth0) Stage 2 of 5 (Device Configure) starting...
Sep 26 18:11:22 spaceship NetworkManager: <info> (eth0): device state change: 4 -> 5
Sep 26 18:11:22 spaceship NetworkManager: <info> Activation (eth0) Stage 2 of 5 (Device Configure) successful.
Sep 26 18:11:22 spaceship NetworkManager: <info> Activation (eth0) Stage 3 of 5 (IP Configure Start) scheduled.
Sep 26 18:11:22 spaceship NetworkManager: <info> Activation (eth0) Stage 2 of 5 (Device Configure) complete.
Sep 26 18:11:22 spaceship NetworkManager: <info> Activation (eth0) Stage 3 of 5 (IP Configure Start) started...
Sep 26 18:11:22 spaceship NetworkManager: <info> (eth0): device state change: 5 -> 7
Sep 26 18:11:22 spaceship NetworkManager: <info> Activation (eth0) Beginning DHCP transaction.
Sep 26 18:11:22 spaceship NetworkManager: <info> dhclient started with pid 26198
Sep 26 18:11:22 spaceship NetworkManager: <info> Activation (eth0) Stage 3 of 5 (IP Configure Start) complete.
Sep 26 18:11:22 spaceship dhclient: Internet Systems Consortium DHCP Client V3.1.1
Sep 26 18:11:22 spaceship dhclient: Copyright 2004-2008 Internet Systems Consortium.
Sep 26 18:11:22 spaceship dhclient: All rights reserved.
Sep 26 18:11:22 spaceship dhclient: For info, please visit http://www.isc.org/sw/dhcp/
Sep 26 18:11:22 spaceship dhclient:
Sep 26 18:11:22 spaceship dhclient: wmaster0: unknown hardware address type 801
Sep 26 18:11:22 spaceship NetworkManager: <info> DHCP: device eth0 state changed normal exit -> preinit
Sep 26 18:11:22 spaceship dhclient: wmaster0: unknown hardware address type 801
Sep 26 18:11:22 spaceship dhclient: Listening on LPF/eth0/00:15:c5:b8:64:fc
Sep 26 18:11:22 spaceship dhclient: Sending on LPF/eth0/00:15:c5:b8:64:fc
Sep 26 18:11:22 spaceship dhclient: Sending on Socket/fallback
Sep 26 18:11:25 spaceship dhclient: DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 3
Sep 26 18:11:26 spaceship dhclient: DHCPOFFER of 118.229.162.208 from 118.229.162.129
Sep 26 18:11:26 spaceship dhclient: DHCPREQUEST of 118.229.162.208 on eth0 to 255.255.255.255 port 67
Sep 26 18:11:26 spaceship dhclient: DHCPACK of 118.229.162.208 from 118.229.162.129
Sep 26 18:11:26 spaceship NetworkManager: <info> DHCP: device eth0 state changed preinit -> bound
Sep 26 18:11:26 spaceship NetworkManager: <info> Activation (eth0) Stage 4 of 5 (IP Configure Get) scheduled...
Sep 26 18:11:26 spaceship NetworkManager: <info> Activation (eth0) Stage 4 of 5 (IP Configure Get) started...
Sep 26 18:11:26 spaceship NetworkManager: <info> address 118.229.162.208
Sep 26 18:11:26 spaceship NetworkManager: <info> prefix 25 (255.255.255.128)
Sep 26 18:11:26 spaceship NetworkManager: <info> gateway 118.229.162.129
Sep 26 18:11:26 spaceship NetworkManager: <info> nameserver '211.68.71.4'
Sep 26 18:11:26 spaceship NetworkManager: <info> nameserver '211.68.71.5'
Sep 26 18:11:26 spaceship NetworkManager: <info> domain name 'bupt.edu.cn'
Sep 26 18:11:26 spaceship NetworkManager: <info> Activation (eth0) Stage 5 of 5 (IP Configure Commit) scheduled...
Sep 26 18:11:26 spaceship NetworkManager: <info> Activation (eth0) Stage 4 of 5 (IP Configure Get) complete.
Sep 26 18:11:26 spaceship NetworkManager: <info> Activation (eth0) Stage 5 of 5 (IP Configure Commit) started...
Sep 26 18:11:26 spaceship avahi-daemon[6076]: Joining mDNS multicast group on interface eth0.IPv4 with address 118.229.162.208.
Sep 26 18:11:26 spaceship dhclient: bound to 118.229.162.208 -- renewal in 11606 seconds.
Sep 26 18:11:26 spaceship avahi-daemon[6076]: New relevant interface eth0.IPv4 for mDNS.
Sep 26 18:11:26 spaceship avahi-daemon[6076]: Registering new address record for 118.229.162.208 on eth0.IPv4.
Sep 26 18:11:27 spaceship NetworkManager: <info> (eth0): device state change: 7 -> 8
Sep 26 18:11:27 spaceship NetworkManager: <info> Policy set (eth0) as default device for routing and DNS.
Sep 26 18:11:27 spaceship NetworkManager: <info> Activation (eth0) successful, device activated.
Sep 26 18:11:27 spaceship NetworkManager: <info> Activation (eth0) Stage 5 of 5 (IP Configure Commit) complete.
Sep 26 18:11:31 spaceship ntpdate[26308]: no server suitable for synchronization found