plz tell when datalink layer makes a significant contribution and when it is negligible and how much contribution does it makes.
and 2nd question is that in calculator you have use Earlang B formula out side the IP netork(i.e. you find only call blocking prbablity in PSTN network and after this you have add the header bandwidth and is telling total bandwidth while ignoring the blocking probablity with in the IP network (PLP:paket loss probablity due to overflow in queues and others)).