What is Layer 3 switching technology? Detailed explanation of the application scenarios of Layer 3 switches and Layer 2 switches!

The design of the third layer switch is based on a careful analysis of IP routing. The process that each message in IP routing must go through is extracted, and this process is a very simplified process. The vast majority of messages in IP routing do not contain options, so in most cases, the work of processing message IP options is redundant. The message lengths of different networks are different. In order to adapt to different networks, IP must implement the function of message fragmentation. However, in a full Ethernet environment, the frame length of the network is fixed, so message fragmentation is also a task that can be omitted.

The third layer switching technology does not use the longest address mask matching method of the router, but uses the precise address matching method, which is conducive to the fast search of the hardware. It uses the method of using cache, and the frequently used host routes are placed in the hardware lookup table. Only the items that cannot be matched in this cache will be forwarded through the software. In the process of storage and forwarding, the flow switching method is used. In the flow switching, the first message is analyzed to determine whether it represents a flow or a group of messages with the same source address and destination address.

If the first message has the correct characteristics, the subsequent messages in the identified flow will have the same priority, and the subsequent messages in the same flow will be exchanged to the destination address based on the second layer. In order to achieve high-speed switching, the three-layer switch adopts the flow switching method. It has made improvements in the processing of IP routing, realized a simplified IP forwarding process, and used a dedicated ASIC chip to realize hardware forwarding. In this way, most of the message processing can be realized in hardware, and only a very small number of messages need to be forwarded using software. The forwarding performance of the entire system can be increased thousands of times, and the cost of equipment with the same performance has also been greatly reduced.

What is Layer 3 switching technology? Detailed explanation of the application scenarios of Layer 3 switches and Layer 2 switches!

Layer 2 switches work at the second layer (data link layer) of the OSI model, so they are called layer 2 switches. Layer 2 switching technology is relatively mature. Layer 2 switches are data link layer devices that can identify MAC address information in data packets, forward them according to MAC addresses, and record these MAC addresses and corresponding ports in an internal address table.

(1) Since the switch exchanges data from most ports simultaneously, it requires a very wide switching bus bandwidth. If a Layer 2 switch has N ports, the bandwidth of each port is M, and the switch bus bandwidth exceeds N×M, then the switch can achieve line-speed switching.

(2) Learn the MAC address of the machine connected to the port and write it into the address table. The size of the address table (generally expressed in two ways: one is BEFFER RAM, the other is the MAC table entry value) affects the access capacity of the switch.

(3) Another thing is that Layer 2 switches generally contain ASIC (Application Specific Integrated Circuit) chips that are specifically used to process data packet forwarding, so the forwarding speed can be very fast. Since different manufacturers use different ASICs, it directly affects product performance.

What is Layer 3 switching technology? Detailed explanation of the application scenarios of Layer 3 switches and Layer 2 switches!

A layer 3 switch is a switch with some router functions. The most important purpose of a layer 3 switch is to speed up data exchange within a large LAN. The routing function it has also serves this purpose, enabling one-time routing and multiple forwarding. Regular processes such as packet forwarding are implemented by hardware at high speed, while functions such as routing information update, routing table maintenance, routing calculation, and routing determination are implemented by software. Layer 3 switching technology is layer 2 switching technology + layer 3 forwarding technology.

Traditional switching technology operates on the second layer of the OSI network standard model - the data link layer, while three-layer switching technology implements high-speed forwarding of data packets on the third layer of the network model, which can not only realize network routing functions, but also achieve optimal network performance according to different network conditions.

1. High-speed data forwarding is achieved through hardware combination.

2. This is not a simple superposition of a Layer 2 switch and a router. The Layer 3 routing module is directly superimposed on the high-speed backplane bus of the Layer 2 switch, breaking through the interface rate limit of traditional routers, and the rate can reach tens of Gbit/s. Including the backplane bandwidth, these are two important parameters of the performance of the Layer 3 switch.

3. Simple routing software simplifies the routing process.

4. Most of the data forwarding, except for the necessary routing selection handled by the routing software, is forwarded at high speed by the second-layer module. Most of the routing software is processed and highly efficient optimized software, and is not simply copied from the software in the router.

What is Layer 3 switching technology? Detailed explanation of the application scenarios of Layer 3 switches and Layer 2 switches!

Layer 2 switches are used in small LANs. In small LANs, broadcast packets have little impact. The fast switching function, multiple access ports and low price of Layer 2 switches provide a perfect solution for small network users.

The most important function of a layer 3 switch is to speed up the fast forwarding of data within a large LAN, and adding routing functions also serves this purpose. If a large network is divided into small LANs according to departments, regions, and other factors, this will lead to a large number of Internet visits, which cannot be achieved by simply using a layer 2 switch; generally speaking, in a network with large intranet data traffic and requiring fast forwarding response, if all of this work is done by a layer 3 switch, it will cause the layer 3 switch to be overloaded and the response speed will be affected. It is a good networking strategy to let the router complete the routing between networks and give full play to the advantages of different devices. Of course, the premise is that the customer's pockets are very fat, otherwise they will have to settle for the second best and let the layer 3 switch also serve as Internet interconnection.