The difference between two-layer equipment and three-layer equipment--summary

1. Computer network

People who have studied computer networks know that the network is hierarchical. The execution process is very similar to the post office. For example, a letter from the province to a country, post office order is the province post office, City Post office, County Post Office, town post office. First-level, and eventually to the countryside. ISO gives the network standard is seven layer, and the actual network is four layer, namely physical layer, Data link layer, network layer, application layer. Traditional network devices typically work on the data link layer and the network layer, such as switches, routers. At present, some network control devices work in the application layer, which is used for the analysis of the application layer of the message, application identification and audit.

2, two-layer equipment and three-layer equipment

A two-tier device is a device on the work Data link layer. The two-tier switch can identify the MAC address information in the packet, forward it according to the MAC address, and record the MAC address with the corresponding port in an internal address table. The specific workflow is as follows:
(1) When the switch receives a packet from a port, it reads the source MAC address in the header, so that it knows the source MAC address of the machine is connected to which port;
(2) to read the destination MAC address in the header, and find the corresponding port in the Address table;
(3) If the table has a port corresponding to this destination MAC address, the packet is copied directly to this port;
(4) If the corresponding port is not found in the table to broadcast the packet to all ports, when the destination machine responds to the source machine, the switch can learn the destination MAC address and which port corresponding to the next transfer of data will no longer need to broadcast all the ports.
Continuous cycle of this process, for the entire network of MAC address information can be learned, the second layer of the switch is to establish and maintain its own table of addresses.

A three-tier device is a device that works on the network layer. Routers are the most commonly used three-tier device that uses different network ID numbers (that is, IP addresses) to determine the address of the data forwarding. IP addresses are implemented in software, describing the network where the device resides, and sometimes these third-tier addresses are referred to as protocol addresses or network addresses.

The difference between two-layer equipment and three-layer equipment--summary