Hi,
i got ans to some of ur query
1) B.W is defined as in a digital communication system, bandwidth has a dual meaning. In the technical sense, it is slang for baud, the rate at which symbols may be transmitted through the system. It is also used to describe channel capacity, the rate at which bits may be transmitted through the system.
2) L2 means datalink layer and l3 means network layer.
l2 u will find mac address
l3 u will find IP address
l2 device is for eg a switch coz it can read the mac add info in the packet
l3 device is a router as it can read the ip datagram
3) load balanacing as used in case of ISDN to share load beth for eg 2 B channels when it exceeds certain threshold.
6) if u know port number u can block to some extent