OSI Layer-7 model (1)

The OSI Layer-7 model enables reliable communication between different networks of different systems through seven hierarchical structural models. Therefore, its primary function is to help different types of hosts implement data transmission.

The node that completes the relay function is usually called a relay system. In the OSI Layer-7 model, the relay systems at different layers have different names.

The layer at which a device works depends on the Data header information used during its operation. When a bridge works, it determines the forwarding Port Based on the MAC header. Therefore, it is obviously a device at the data link layer.

Specifically:

Physical Layer: Nic, network cable, Hub, repeater, Modem

Data link layer: bridge, switch

Network Layer: vro

The gateway works on the layer 4 transmission layer and above.

A hub is a physical layer device that transmits information in the form of broadcast.

A vswitch is a machine used for Packet Exchange. Most of them are link layer devices (L2 switches). They can perform address learning and exchange messages in the form of storage forwarding ..

One role of a router is to connect different networks, and the other is to select the information transmission line. By selecting smooth and fast routes, You can greatly increase the communication speed, reduce the communication load of the network system, save network system resources, and improve the network system accessibility.

Differences between vswitches and vrouters

The vswitch has a high-bandwidth back bus and an internal switching matrix. All the ports of the switch are attached to this bus. After the control circuit receives the data packet, the processing port searches for the address table in the memory to determine the target MAC address (the hardware address of the NIC) NIC connected to which port, data packets are quickly transmitted to the destination port through the internal switching matrix. If the destination MAC does not exist, the packets are broadcast to all ports, after receiving the port response, the switch "learns" the new address and adds it to the internal MAC address table.

You can also use a vswitch to segment the network. By comparing the MAC address table, the vswitch only allows necessary network traffic to pass through the vswitch. Through the filtering and forwarding of vswitches, the broadcast storm can be effectively isolated to reduce the occurrence of incorrect packets and wrong packets, so as to avoid sharing conflicts.

A vswitch can transmit data between multiple port pairs at the same time. Each port can be considered as an independent network segment, and the network devices connected to it enjoy all the bandwidth alone, so they do not need to compete with other devices. When node A sends data to node D, Node B can send data to node C at the same time, and both transmission enjoy all the bandwidth of the network and all have their own virtual connections. If a 10 Mbps Ethernet switch is used here, the total traffic of the switch is 2*10 Mbps = 20 Mbps. When a 10 Mbps shared HUB is used, the total traffic of a HUB does not exceed 10 Mbps.

In short, a vswitch is a network device that can encapsulate and forward data packets based on MAC address recognition. The switch can "Learn" the MAC address and store it in the internal address table. By creating a temporary exchange path between the initiator of the data frame and the Target receiver, the data frame can directly reach the destination address from the source address.

From the perspective of filtering network traffic, the role of a router is very similar to that of a switch and a bridge. However, unlike switches that work on the physical layer and divide network segments physically, vrouters use specialized software protocols to logically divide the entire network. For example, a router that supports the IP protocol can divide the network into multiple sub-network segments. Only network traffic directed to a Special IP Address can pass through the router. For each received packet, the router recalculates its verification value and writes it to a new physical address. Therefore, the speed of data forwarding and filtering by vro is usually slower than that of A vswitch that only views the physical address of a data packet. However, vrouters can improve the overall efficiency of networks with complex structures. Another obvious advantage of a vro is that it can automatically filter network broadcasts.