Spanning- Tree Protocol (STP) as defined in the IEEE 802.1D is a link management protocol that provides path redundancy while preventing undesirable loops in the network. For an Ethernet network to function properly, only one active path can exist between two stations. Loops occur in networks for a variety of reasons. The most common reason you find loops in network is the result of a deliberate attempt to provide redundancy- in case one link or switch fails, another link or switch can take over.

Bit rate is the number of bits transmitted during one second whereas baud rate refers to the number of signal units per second that are required to represent those bits. Baud rate= bitrate/N where N is no of bits represented by each signal shift.

Tunneling is a mechanism provided to transfer data securely between two networks. The data is split into smaller packets and passed through the tunnel. The data passing through the tunnel has 3 layers of encryption. The data is encapsulated. Tunneling can be approached by Point to Point tunneling protocol.

Voluntary Tunneling:
Users computer is an end point of the tunnel and acts as tunnel client. Here the client or user issues a request to configure and create a voluntary tunnel. They require a dial up or LAN connection. Example of dial up connection is internet at home where a call is made to the ISP and connection is obtained.

Compulsory tunneling:
In compulsory tunneling, instead of the user a vpn remote access server configures and creates a tunnel. Hence, the end point is the Remote sever not the user.

Tunnels that are created manually are static tunnels. Tunnels that are auto discovered are dynamic tunnels. In dynamic tunneling, tcp connections can be checked dynamically. If no connections exist that are routed through the tunnel, a check for more suitable gateway can be done. Static tunneling may at times require dedicated equipment's.