1) switch

In computer network system, the switch is in view of the weaknesses and Shared work mode, the switch has a high bandwidth of the back of the bus and internal exchange matrix, all switch ports are articulated in the back of the bus, when control circuit receives packets processing port looks in memory in order to determine the destination MAC address table (network adapter hardware address) of the NIC (NIC) articulated in which port, through internal exchange matrix quickly to send the packet to the destination port, if the destination MAC does not exist, switch to broadcast to all ports, exchange the opportunity to "learn" after receiving port in response to the new address, and put it in the internal address table,

Switches in the second layer of the OSI reference model, namely the data link layer, the inside of the switch when the CPU will succeed in each port connection, through the study of ARP agreement its MAC address, save into an ARP table, in the future communication, sent to the MAC address of the packet will only be sent to the corresponding port, port, but not all, therefore, switches can be used to broadcast the data link layer, namely collision domain; But it can not divided radio network layer, namely the broadcast domain,

Switches are widely used in network exchange on the second floor, commonly known as "layer 2 switches,"

The types of switches: layer 2 switches, layer 3 switches, layer 4 switches, seven layer switches work the second layer in the OSI seven layer model respectively, the third layer, layer 4 box of 7 layers, and hence the name,



2) router
Router (Router) is a computer network equipment, provides the routing and forwarding two important mechanisms, may decide to end packets from the source to a destination after the routing path (transmission path between the host and the host), a process called routing; The router at the input packets transferred to appropriate router output (inside the router), which is referred to as a turn, routing work in the third layer of the OSI model - that is, network layer, such as the Internet protocol,

A function of the router is connected to different networks, another role is to choose the information transmission lines, the difference of routers and switches, routers belongs to OSI layer 3 products, is the OSI layer 2 switch products especially layer 2 switches (here),

3) the gateway

Gateway (Gateway), as its name implies is the Gateway to connect two networks equipment, different from the Router (due to historical reasons, many once put the literature of the TCP/IP network layer using a Router, the Router called Gateway, in a lot of local area network (LAN) used today is the route to access networks, so it is usually refers to the Gateway Router IP), often in the home or small business network in use, used to connect LAN and Internet, the Gateway also often refers to a kind of agreement to another device, such as voice gateways,