To get utilization over a day:

1) search the syslogs for a given days entries

2) dig out relevant entries for PPP and ARAP connections starting and
ending, and convert to a timestamped list of login/logout events

egrep 'Connection | IPCP Active | Port Logout' | colrm 1 7 | colrm 6 8 | awk '{print $1" " $9" " $10}' | sed 's/Startup/login/' | sed 's/Connection established/login/' | sed 's/Port Logout/logout/' | sed 's/Connection terminated/logout/' > calldata

3) use useage.c to generate table, suitable for xgraph, of percent
ports used over time of day

This procedure is implemented in gencallgraph.