1. What are the three key technologies of LAN?
(1) topology; (2) transmission medium; (3) medium access control method
2. What are the topological structures of LAN? What are the characteristics of each topology?
(1) Bus topology
Features:
All nodes are directly connected to a bus as a common transmission medium through network adapters;
The information sent by any node on the bus is transmitted along the bus, and other nodes can receive the information, but at the same time, only one node is allowed to send data;
It may happen that two or more nodes use the bus to send data at the same time, and "conflict" will occur, resulting in transmission failure.
(2) Ring topology
Features:
All nodes are connected to the shared transmission medium using network adapters, and form a closed loop through point-to-point connections;
The data in the ring is transmitted around the ring nodes in one direction;
In a ring topology, although multiple nodes share a ring path, collisions do not occur because some method of media access control is used to determine when each node in the ring sends data.
(3) Star topology
Features:
There is a central node in the star topology, and each node is connected to the central node through a point-to-point line.
3. Briefly describe the working principle of carrier sense multiple access/collision detection (CSMA/CD)
It can be summarized as listening before sending, listening while sending, conflict stop sending, and random resending.
(1) Before sending information, each node must first monitor whether there is information being transmitted on the bus. If there is, other nodes will not send information to avoid damaging the transmission; if not, they can send information to the bus.
(2) When a node occupies the bus to send information, it must detect the bus while sending to see if there is a conflict.
(3) After the sending node detects the conflict, it immediately stops sending information and strengthens the conflict signal,
(4) Then use the algorithm to wait for a period of time before listening to the line again, and prepare to resend the information.
4. What are the Ethernet standards of 10Mbit/s?
For 10Mbit/s, IEEE802.3 has four physical layer specifications, namely, thick cable Ethernet (10base-5), thin cable Ethernet (10base-2), twisted pair Ethernet (10base-T), fiber optic Ethernet (10base-F)