Computer Networks
Thursday, April 09, 2009 Posted In CS and IT Edit This
Q-1:
Question No.2
i. If we can extend the LAN then why we need a WAN?
Generally we extend LANs (Local Are Networks) using repeaters. But the maximum number of repeaters that can be used is limited by the Ethernet standard to be four.
In Ethernet LAN, the maximum length of the segment is fixed and the maximum number of nodes in a segment is also fixed for the particular type of Ethernet LAN.
Therefore we cannot indefinitely extend LANs..so we need WAN
ii. How can a bridge know whether to forward frames?
The bridge uses the MAC address in the frame for forwarding. It only forwards the frame from one segment to another segment if it is necessary. The bridges will come to know where to send the frame by learning using the source addresses of the frames.
iii. Can the length of an Ethernet be increased to many segments of 500 meter each merely by adding a repeater to connect each additional segment?
The Ethernet standards have limited the maximum number of repeaters to be used to four.
SO there can only be five segments each with a maximum length of 500m therefore overall length is 2500 meters.
So the length of the Ethernet cannot be increased to many segments of 500 meters each by merely adding a repeater to connect each segment.
iv. How can a computer attach to a network that sends and receives bits faster than the computer’s CPU can handle them?
The data to be sent will be placed in buffer (some space) before and then the data will be transmitted. The data may be present in the buffer till the sender gets an acknowledgement from the receiver saying that the data has been received (like in TCP).
Similarly the data will be received into a buffer first...after that the data from the buffer will be forwarded to CPU for further processing etc
Question No.2
i. If we can extend the LAN then why we need a WAN?
Generally we extend LANs (Local Are Networks) using repeaters. But the maximum number of repeaters that can be used is limited by the Ethernet standard to be four.
In Ethernet LAN, the maximum length of the segment is fixed and the maximum number of nodes in a segment is also fixed for the particular type of Ethernet LAN.
Therefore we cannot indefinitely extend LANs..so we need WAN
ii. How can a bridge know whether to forward frames?
The bridge uses the MAC address in the frame for forwarding. It only forwards the frame from one segment to another segment if it is necessary. The bridges will come to know where to send the frame by learning using the source addresses of the frames.
iii. Can the length of an Ethernet be increased to many segments of 500 meter each merely by adding a repeater to connect each additional segment?
The Ethernet standards have limited the maximum number of repeaters to be used to four.
SO there can only be five segments each with a maximum length of 500m therefore overall length is 2500 meters.
So the length of the Ethernet cannot be increased to many segments of 500 meters each by merely adding a repeater to connect each segment.
iv. How can a computer attach to a network that sends and receives bits faster than the computer’s CPU can handle them?
The data to be sent will be placed in buffer (some space) before and then the data will be transmitted. The data may be present in the buffer till the sender gets an acknowledgement from the receiver saying that the data has been received (like in TCP).
Similarly the data will be received into a buffer first...after that the data from the buffer will be forwarded to CPU for further processing etc
