Layer Fourth Exchange technology-the typical quality of service

With the popularization of broadband, a variety of network applications in depth, our local area network is shouldering heavy traffic. Network system of audio, video, data and other information transmission is full of bandwidth consumption, we have to provide these data traffic differentiated services, so that the time delay sensitive and important data first pass, this has to consider the fourth layer Exchange to meet policy-based scheduling, QoS (Quality of Service: Quality of services and requirements for security services.

the difference between the exchange of two and three or four layers

The second layer Exchange realizes the fast information exchange between the hosts in the LAN, and the third layer Exchange is the perfect combination of the Exchange technology and the routing technology, while the fourth layer Exchange technology can provide the optimal allocation for the network application resources, realize the service quality, load balance and security control of the application service. Four-tier exchange is not to replace who, in fact, now the two-tier exchange and three-tier exchange has been integrated into four-layer switching technology.

The second layer switch completes the End-to-end data exchange based on the MAC address and MAC address Table of the second layer data link layer. The second layer switch only needs to identify the MAC address in the data frame, and forwards it directly according to the MAC address, so it is very convenient to use ASIC special chip to realize. The second layer of the Exchange solution, is a "Everywhere Exchange" scheme, although the scheme can be divided into subnets, limited broadcast, set up VLAN, but its control capacity is small, flexible enough, also unable to control traffic, lack of routing function.

The third layer switch is based on the third layer of network layer IP address to complete end-to-end data exchange, mainly applied to different VLAN subnet routing. When the first data flow of an information source is exchanged (routed) at the third level, the switch generates a map of the MAC address and IP address and stores the table as a subsequent stream of information sources enters the switch, and the switch will be based on the first generated and saved address mapping table, Directly from the second layer from the source address to the destination address, no longer through the third routing system processing, improve the efficiency of packet forwarding, to solve the VLAN subnet transmission of information between the traditional router generated speed bottleneck.

Layer Fourth switch can not only complete end-to-end exchange, but also according to the application characteristics of port host, determine or limit its exchange traffic. Simply put, the fourth layer switch is based on the Transport Layer Packet exchange process, is a class of TCP/IP protocol Application layer user application Exchange requirements of a new LAN switch. Layer fourth switches support all protocols below the TCP/UDP layer fourth, which can differentiate the application type of the packet according to the TCP/UDP port number to achieve the access control and service quality assurance of the application layer. You can view the contents of the third-tier data header source and destination addresses, and you can implement the key functions of bandwidth allocation, fault diagnosis, and access control to TCP/IP application Data flow based on observed information. The fourth layer switch optimizes the network through task assignment and load balance, and provides detailed traffic statistic information and accounting information, which solves the problems of network congestion, network security and network management at the application level, and makes the network intelligent and manageable.