关于调试ppp断线的问题

lbtianya

我写了一个modem 的驱动程序,在测试时数据在33kbps时连续收发数据都没有问题.
当挂上ppp后,发现当速度>15Kbps时,ppp过30s后就会断线,而且不能自动恢复.

我的ppp配置参数如下
# /etc/ppp/options (NO PAP/CHAP)
#
# Prevent pppd from forking into the background
-detach
#
# use the modem control lines
modem
# use uucp style locks to ensure exclusive access to the serial device
lock
# use hardware flow control
crtscts
# create a default route for this connection in the routing table
defaultroute
# do NOT set up any "escaped" control sequences
asyncmap 0
# use a maximum transmission packet size of 552 bytes
#mtu 552
# use a maximum receive packet size of 552 bytes
#mru 552
#
#-------END OF SAMPLE /etc/ppp/options (no PAP/CHAP)
当mtu=552 mru=552时,5s后就短线.默认是1500,不知到关我的内核或ppp参数配置有没有什么关系?