Hi
--- > is there a way if we can see anywhere the total bandwidth alloted by the service provider
The SP will allocate the bandwidth as per your instruction & That is using Rate limit in PE router.
SP will configure the rate limit on PE to limit the bandwidth.
http://www.cisco.com/en/US/docs/ios/12_0/qos/command/reference/qrcmdr.html#wp1017761
---- > we need to configure it manually
You don't need to configure the bandwidth and Bandwidth command never limit the bandwidth on interface , the use of bandwidth command is to set the bandwidth on interface & that is used for calculation of metric in dynamic routing or it is user when you plan to configure QOS.
---- > how can we calculate actual link utilization on any given link/interface
So see the acutal usage , you can use bandwidth monitoring tools like PRTG , Solar wind, Whatsup, Cacti etc. & for that you need to configure SNMP string on router to pull data by this tools. ( Use PRTG Traffic Grapher is easy & good for actual bandwidth monitoring ).
And for more detailed you can use Netflow analyzer for deep inspection of traffic but for that you need to configure netflow in routers.
http://demo.netflowanalyzer.com/netflow/jspui/NetworkSnapShot.jsp
Regards
Chetan Kumar
http://chetanress.blogspot.com