Your log shows:
00:02:13:44 L3      IP: (vcc1) Physical Link Active
00:02:13:44 L3      IP: (vcc1) IP Protocol Up
00:02:14:47 L3      DSLU: dsl_ALC_GetCcounters : Link Failure
00:02:14:47 L3      DSLU: dsl_ALCresponses : Close Successful
00:02:14:47 L3      DSLU: dsl_ALCperiodic : Link lost
00:02:14:47 L4      ATM: PHY layer has gone down
00:02:14:47 L3      IP: (vcc1) Physical Link Down

Link has failed
Re-Sync process begins below. Notice it's 15 seconds from failure to up again.
A loss of sync has all the negative words (lost, down, failure).

00:02:15:00 L3      DSLU: dsl_ALCresponses : Connect Successful
00:02:15:00 L3      DSLU: dsl_ALCperiodic : Link Connected
00:02:15:01 L4      ATM: PHY layer is up, waiting for cell delineation
00:02:15:01 L4      ATM: Cell lock detected
00:02:15:02 L4      ATM: Cell lock verified
00:02:15:02 L3      IP: (vcc1) Physical Link Active
00:02:15:02 L3      IP: (vcc1) IP Protocol Up
00:02:15:18 L4      TS: User "" completed login as user {this is me logging in}