What does topological stacking mean?

Stacking technology Extended stacking technology is another technology widely used in expanding ports on Ethernet switches at present, and it is a non-standardized technology. Mixed stacking between vendors is not supported, and the stacking method is determined by each vendor, and topology is not supported. At present, there are two popular stacking modes: daisy chain mode and star mode. The biggest advantage of stacking technology is to provide simplified local management and manage a group of switches as one object. Daisy Chain Stacking Daisy Chain Stacking is a stacking technology based on cascade structure, which has no special requirements for switch hardware. Through the relatively high-speed port cascade and software support, the multi-switch cascade structure is finally realized, and a certain degree of redundancy can be realized through the loop. However, in terms of switching efficiency, the peer-to-peer connection mode is at the same level. Daisy chain stacking usually has a mode of using one high-speed port and two high-speed ports, and their structures are shown in Figure 2. In the mode of using high-speed port (GE), uplink and downlink are sent and received at the same port, and finally a ring structure is formed. The data exchange between any two member switches needs to go around the ring and pass through the switch ports of all switches, which is very inefficient, especially when there are many stacked layers, and the stacked ports will become a serious system bottleneck. Using two high-speed ports to realize daisy-chain stacking, because more high-speed ports are occupied, you can choose to realize ring redundancy. Compared with cascade mode, daisy-chain stacking mode has no topology management and generally cannot be distributed. It is suitable for single-node mechanism with high-density port requirements and can be used at the edge of the network. The daisy chain structure needs to eliminate the broadcast storm brought by the loop. Under normal circumstances, at any time, a slave switch in the loop can only reach the master switch through a high-speed port (that is, a high-speed port cannot share the uplink data pressure of this switch), and it needs to be exchanged through all the uplink switches (see Figure 3). Daisy-chain stacking is a simplified stacking technology, mainly an extended port technology to provide centralized management. The forwarding efficiency between multiple switches has not been improved (the efficiency in single-port mode will be much lower than that in cascade mode), so hardware needs to provide more high-speed ports, and software needs to realize uplink redundancy. Generally speaking, the number of daisy chain stacks should not exceed four, and all members of the stack group should be placed close enough (usually on the same rack). Star stacking technology is an advanced stacking technology. For switches, it is necessary to provide an independent or integrated high-speed switching center (stacking center). All stacking hosts go up to the unified stacking center through dedicated (or universal) high-speed stacking ports. Stacking center is usually a hardware switching unit based on special ASIC. According to its switching ability, the bandwidth is generally between 10-32g, and its ASIC switching ability limits stacking. Star Stacking Star Stacking technology reduces the number of stages of all stack group member switches reaching the stack center matrix to one level, and the forwarding between any two end nodes only needs three exchanges, and the forwarding efficiency is the same as that of the edge node communication structure in the first-level cascade mode. Therefore, compared with the daisy chain structure, it can significantly improve the data forwarding rate among stack members, and at the same time provide a unified management mode, and a group of switches can appear as a single node in network management. Star stacking mode is suitable for single-node LAN that needs high efficiency and high density ports. Star stacking mode overcomes the influence of high delay of multi-stage forwarding in daisy-chain stacking mode, but it needs to provide a high-bandwidth matrix, and the matrix interface is generally not universal, so neither the stacking center nor the stacking ports of member switches can be used to connect other network devices. Using highly reliable and high-performance matrix chips is the key to star stack. Generally, the bandwidth of stacked cables is between 2g and 2G-2.5G (bidirectional), which is slightly higher than that of general GE. The higher part is usually only used for membership management, so the effective data bandwidth is basically the same as GE. However, due to the special bus technology involved, the cable length generally cannot exceed 2m. Therefore, in star stacking mode, all switches need to be confined to one rack. It can be seen that the traditional stacking technology is a centralized management port expansion technology, which can not provide topology management, has no international standards and has poor compatibility. However, in a single-node LAN that requires a large number of ports, star stacking can provide excellent forwarding performance and convenient management features. Cascading is the basis of building a network, and various topologies and redundant technologies can be used flexibly. When there are too many layers, it needs careful design. For networks with few cascade levels, cascading can provide the best performance. For example, in a point that needs to be expanded to twice the number of ports, it needs to be exchanged between the edges of the star stack three times and between the cascade mode and the daisy-chain stack twice. The star stack mode needs more investment and the daisy-chain stack mode needs to occupy more high-speed ports, so ordinary cascade becomes the most economical and efficient construction method. In addition, you can also use the existing switching equipment without repeated investment, but these two equipments need to be managed separately (see Figure 5). The application of traditional stacking technology is often limited by geographical location and often needs to be placed in the same rack, which will bring difficulties to wiring when applied to high-density ports. Therefore, major manufacturers are actively seeking to support distributed stacking technology. At present, Huawei's Quidway S series Ethernet switch products and Cisco series Ethernet switch products both provide cluster management mode. Quidway S series Ethernet switches adopt Huawei's unified VRP operating system and unified iManager network management system. The network management system supports Chinese interface, adopts standard protocol and open technology, and is fully compatible with mainstream network management platforms. Under the guidance of Huawei's "four full line speeds" of layer 2 switching, layer 3 switching, service switching and QoS service, Quidway S series Ethernet switches make full use of the late-developing advantages of product development, meet the requirements of broadband metropolitan area networks and enterprise networks in terms of product system design, expansion capability and rich service characteristics, and can provide customers with more efficient, secure and easy-to-expand customized solutions. Taking Huawei's product (HGMP) as an example, with the support of cluster management mode, centralized configuration and management can be realized on the network constructed by using Quidway series switches through general cascade mode, and a LAN can join as a group. For the network management system, a group can be represented as the same device and managed with an IP address, which is equivalent to or even better than the management effect of the previous stacked groups. As a concentrated expression of universality, group member switches can realize the topology design and distributed placement of members in the group, and the stacking ports can choose the general ports supported by devices or use port aggregation, so that users can gain the ability to flexibly control the stacking bandwidth of the switching network, thus achieving higher flexibility requirements. For different environments, the effect of choosing different port expansion modes is inconsistent.