Layer-4 Switch Integrated Application

The layer-4 switch is quite common. So I studied the comprehensive application of the layer-4 switch and shared it with you here. I hope it will be useful to you. With the popularization of broadband and the deepening of various network applications, our local network is undertaking heavy business traffic.

The amount of transmitted audio, video, data, and other information in the network system is full of bandwidth. We have to provide differentiated services for these data traffic, so that latency-sensitive and important data is prioritized, therefore, layer-4 switches must be considered to meet the needs of policy-based scheduling, QoSQualityofService: service quality) and security services.

Ii. Differences between layer-4 vswitches

Layer-2 exchange enables fast information exchange between hosts in the LAN. layer-3 Exchange is a perfect combination of exchange technology and routing technology, the layer-4 switch technology can provide optimal allocation for network application resources to achieve application service quality, load balancing, and security control. The layer-4 switching is not a replacement. In fact, the layer-2 switching and layer-3 switching are now integrated into the layer-4 switching technology.

The second layer switch performs 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 forward it directly based on the MAC address, which is very easy to implement using ASIC dedicated chip. The second-layer switch solution is a "Everywhere switch" solution. Although it can also divide subnets, restrict broadcast, and establish VLANs, it has low control capabilities and is not flexible enough, it cannot control traffic and lacks the routing function.

A layer-3 Switch performs end-to-end data exchange based on the layer-3 network layer IP address. It is mainly used for routing between different VLAN subnets. After the first data stream of a certain source performs layer-3 switching routing, the switch generates a MAC ing table between the MAC address and IP address, and stores the table, if subsequent data streams from the same information source enter the vswitch again, the vswitch will directly transfer the source address to the destination address from the second layer based on the address ing table generated and saved for the first time, instead of being processed by the third route system, this improves the data packet forwarding efficiency and solves the speed bottleneck of traditional routers when information is transmitted between VLAN subnets.

The layer-4 switch not only performs end-to-end switching, but also determines or limits the switching traffic based on the Application Characteristics of the port host. To put it simply, the layer-4 switch is based on the packet exchange process at the transport layer. It is a new type of LAN switch based on the Application exchange requirements at the TCP/IP application layer. The layer-4 switch supports all protocols below the layer-4 of TCP/UDP. You can distinguish the application types of data packets based on the TCP/UDP port numbers to achieve access control at the application layer and ensure service quality. You can view the content of the source address and destination address of the third-level data packet header. You can take corresponding actions based on the observed information, implement the key functions of bandwidth allocation, fault diagnosis, and access control over TCP/IP application data streams. The layer-4 switch optimizes the network through task allocation and Server Load balancer, and provides detailed traffic statistics and accounting information, in this way, network congestion, network security, and network management are solved at the application level, so that the network can be intelligent and manageable.

Introduction to layer-4 Switching Technology

The fourth layer of the OSI network reference model is the transport layer. The transport layer is responsible for end-to-end communication, that is, coordinated communication between the network source and the target system. In the IP protocol stack, This is the protocol layer of TCP transmission control protocol) and UDP User Datagram Protocol. TCP and UDP contain port numbers, which uniquely differentiate which application protocols are contained in each packet, such as HTTP, FTP, and telnet ). The additional information provided by TCP/UDP port numbers can be used by network switches. layer-4 switches use this information to distinguish packet data, which is the basis of layer-4 switches.

The main functions of layer-4 switching are as follows: 1. Data Packet Filtering: On a traditional router, the layer-4 Information port number is used to define the access control list filtering rule. Layer-4 Switching also uses the concept of control list, but unlike software-based routers, layer-4 switching is implemented in ASIC dedicated high-speed chips, so that the filtering control can be implemented at line rate.

1. Service Quality: The layer-4 Information of TCP/UDP can also be used to establish the priority of Application Communication. Layer-4 switching allows the use of port-based applications) to differentiate priorities and set priority queues to ensure that important traffic, such as VOIP and video, is processed as quickly as possible, enable emergency applications to obtain high-level network services.

2. Server Load balancer: the principle of layer-4 Server Load balancer is to exchange virtual connections based on IP addresses and TCP ports, and send data packets directly to the corresponding ports of the target computer. A switch with layer-4 Switching capabilities can act as a hardware Load balancer to achieve server load balancing. Because the layer-4 switching is based on the hardware chip, the performance is very good. Especially for the speed of network transmission, the switching speed far exceeds the normal packet forwarding speed. The layer-4 switch is used. All cluster hosts are connected to the external Internet through the layer-4 switch. When an external customer asks a server, the layer-4 switch dynamically allocates the server to achieve dynamic load balancing, when one of the servers fails, the switch dynamically distributes all traffic to other hosts in the cluster.

3. host backup connection: the host backup connection provides redundant connections to port Devices to effectively protect the system in the event of a switch failure. This service allows you to define a Master/Slave switch, as defined in a virtual server, they have the same configuration parameters. Because the layer-4 switch shares the same MAC address, the backup switch receives the same data as the master unit. This enables the backup switch to monitor the communication content of the master switch service. The primary switch continuously notifies the backup switch of data, MAC data, and its power status at Layer 4. When the primary switch fails, the backup switch automatically takes over without interrupting the conversation or connection.

4. Statistics and report: by querying layer-4 data packets, layer-4 switches can provide more detailed statistics records. Because the administrator can collect more detailed information about which IP address to communicate with, and even collect communication information based on which Application Layer Service is involved in the communication. When the server supports multiple services, these statistics are particularly effective for examining the load of each application on the server. The added statistical service is also useful for Server Load balancer connections using vswitches. Including detailed real-time reports and historical reports. The comprehensive report function provides administrators with full control over bandwidth resources, so that enterprises can make more appropriate business decisions. Layer-4 switches are commonly called "application switches" in the industry. The following are some well-known switches:

BIG-IP2400 series application switches from F5 USA support customized load balancing, traffic prioritization, policy-based traffic guidance, source, destination, and application exchange. Radware's webserverctor ctor Application Switch ensures the full availability, optimized operation, and complete security of Server Clusters, so as to ensure high reliability and performance for applications within the network and data center. American Foundry ServerIronGT-C2404F Application Switch can realize global server load balancing, high performance VPN/firewall load balancing, transparent cache switching, link load balancing, anti DoS attack protection server.

Summary:

With the development of network information systems from small to medium-sized to large, the exchange technology also evolved from the original MAC address-based exchange to IP address-based exchange, this article provides a comprehensive introduction to layer-4 switching technology, and now some products propose layer-7 switching based on content ). It can be seen that the continuous development of network exchange technology has changed from data-based exchange to application-based exchange, which not only improves the network access speed, but also constantly optimizes the overall network performance.