Alcatel-Lucent 7750 SR OS Interface Configuration Manual page 46

Port Features
Timers
Cisco HDLC (cHDLC) has two timers associated with the protocol, the keepalive interval and the
timeout interval. The keepalive interval is used to send periodic keepalive packets. The receiver
process expects to receive a keepalive packet at the rate specified by the keepalive interval. The
link is declared down if the receiver process does not receive a keepalive within the timeout
interval. The link is declared up when the number of continual keepalive packets received equals
the up-count.
It is recommended that the nodes at the two endpoints of the cHDLC link are provisioned with the
same values.
Page 46 7750 SR OS Interface Configuration Guide