Analysis of the advantages and challenges of stackable switches

Tiered switches can multiply the port density of the network access layer by connecting several switches through a dedicated stacking module.

Some manufacturers ' switches can be managed as a network element after stacking, which simplifies the network structure.

Advantages of Stackable Switches

Stackable switches, which have the advantages of rapid deployment, good value, scalability, and ease of management, are now widely used, especially in e-commerce applications.

However, evaluating a tiered switch completely based on the price per user port does not reflect all the circumstances. In fact, if a vendor calculates a per-port price or makes other assertions based on a configuration that does not match the actual conditions, a product may be misleading only based on the price factor.

The challenges of stacking technology

Today's traffic model is diversifying, such as voice and image instant messaging, which makes client-client access soar and traffic between the edge switches growing. These are not what the previous stackable switches have been able to handle.

The first problem encountered is tiered bandwidth. We know that the forwarding capability of a switch usually allows for wire-speed switching between ports, but what is the tiered bandwidth between switches? Take a look at the switches on the market today, and stack bandwidth is usually 1Gbps. The BayStack470 of Nortel Networks can provide 2.5Gbps of tiered bandwidth. But when the traffic across the switch is large, do we need a larger stack bandwidth?

Second, stacking introduces the issue of device reliability. Does it affect the work of other switches when one switch or one stacked cable fails in the entire stack? Network management will not be a problem? How long does it take to get back to normal? Although most of the switches in the market have dedicated stacking modules, they still follow the principle of Gigabit interface interconnection. When multiple switches are connected by a stacked cable into a loop, it looks like a network device, but it's actually like putting them together with a gigabit interface. As a result of Spanningtree, one of these stacked cables is blocked by the protocol, which seriously affects forwarding performance. When a switch or a stacked cable in the entire stack fails, the Spanningtree converges, and the network will have at least 10 seconds of unavailable time, which is unacceptable to today's users. In this case, critical applications such as voice, video, and electronic transactions are severely affected.

In 1995, when the BayStack450 switch came out, Nortel Networks solved these problems. BAYSTACK450 provides "secure stacking" (2.5Gbps), which heals within a second in the event of a failure. This "secure stack" not only provides protection in the event of a device failure, but also provides uninterrupted business protection when the user upgrades the network. With the growth of users ' business, the scale of the network will enlarge. When the access switch needs to be expanded, we inevitably need to open the stack and join the new switch. "Secure Stacking" makes this process not affect the switch that is working. This stacking technique also enables the entire stack to be network-management with an IP address, like a networked device.

The convergence of voice, image, data, and storage services makes more and more businesses web-based, people can do more on their desktops, and the pressure on the edge of the network is growing. In addition to stacking technology, edge switches are challenged in a variety of areas such as performance, reliability, security, QoS, manageability, and more.

Features of stackable Switches

Tiered bandwidth

The biggest problem with tiered switches today is how to solve the problem of stacking bandwidth from hardware. Most of the switches currently on the market are stacked by Gigabit expansion slots, with only 2Gbps of stack bandwidth, which can easily clog up data streams. Therefore, try to choose a product with high stacking bandwidth. Now, stack bandwidth can reach dozens of Gbps.

At present, a number of stacking switches on the market can reach 6 to 9 units, or even higher, this high stacking function can achieve a flexible network expansion. It is important to note, however, that the performance of the switch is not affected while the high stack is implemented.

Stacking mode

Tiered switches typically have two stacking styles: Star stacking and daisy-chained stacking. Daisy chain Stacking is a cascade structure based on cascading technology, there is no special requirements on the hardware of the switch, through relatively high speed port connection and software support, the final implementation of a multiple-switch cascade structure, through the loop, can achieve a certain degree of redundancy. Daisy chain Stacking mode, there is no topology management, suitable for high-density port requirements of a single node mechanism, can be used for network edge. While star stacking mode is suitable for single node LAN with high efficiency and high density port, star stacking mode overcomes the Gao Shiyan effect of daisy chain stacking mode in multi-level forwarding, but it needs to provide high bandwidth matrix, high cost, and matrix interface is generally not universal, Tiered ports for either a tiered hub or a member switch cannot be used to connect to other network devices.