Six steps teach you how to choose a suitable switch in your project
How to choose a switch? How to determine the network structure according to the project? We have this question in most of the projects. The switch is one of the most commonly used equipment in weak current network. This article aims to let everyone know in detail how to choose a switch in the project.
For now, the parameter data of many different brands of switches are good, especially the packet forwarding rate and backplane bandwidth, but it is not good to use, so you need to check the brand when buying a switch.
Huawei, Cisco, Ruijie , H3C and other brands of enterprise-level switches are highly rated, and each has its own merits. As domestic brands, Huawei switch is developing very rapidly in the field of switches. Cisco, as an established company, has a very strong Strength needs to be considered according to the project and its own situation.
- Network scale and hierarchy
What is considered is the network scale and switch application level, which are mainly divided into small and medium networks and large and medium networks.
We recommend you to use the OSI reference model to choose which one is the most suitable. If the company is only doing data forwarding, it is recommended to use a two-layer(L2) switch. If the departments are divided to isolate the departments, it is recommended to choose a three-layer(L3) switch. If you need to set up gateways, firewalls and other functions, you need a more advanced firewall-level switch.
- How to plan the network hierarchy:
The network structure determines what equipment to use. Some small networks only have the core layer and the access layer, so the core switch is relatively better to choose, and the pressure is not great. For example, some small monitoring networks are only used in the internal network. Just choose a Layer 2 switch.
For example, the following network: only access layer and core layer.
Of course, in a large-scale network, it is difficult to coordinate the distribution between the access layer and the core layer. A three-layer structure is required. The core layer and the convergence layer, the access layer, use the convergence layer to break down the pressure of the core switch, which involves the division of VLANs. For functions such as network management, a Layer 3 switch is required.
- The number of ports of the switch
The number of ports of the switch and the number of physical ports supported by the switch determine the number of terminals or secondary receiving devices connected to the switch, which need to be selected according to actual needs. Of course, you also need to consider subsequent network expansion. The access port of the switch is used to connect to the internal network terminal, and the uplink port is used to connect to the upper-level equipment.
If the number of points is around 16, and the number of points does not change much in the long term, you can choose a 24-port switch. If there are more than 16 points, and there are other network equipment, you need to do some redundancy on the number of ports. Otherwise, you can choose a 48-port switch.
Port parameters
Port parameters mainly need to be considered:
Port speed (100M, Gigabit, 10G) and port type (RJ45, SFP/optical port, PoE power supply network port, etc.). There are several optical ports, or several electrical ports, etc., the number of 100M ports and Gigabit ports.
- The function supported
Consider the functional support of the switch, whether it has network management functions, module redundancy, routing redundancy, four-layer switching, scal ability, etc. At the same time, the security function of the switch needs to be considered.
Specific examples include: access control, 802.1X authentication, loop back detection, four-element binding, IGMP Snooping, etc.
- Backplane bandwidth
Backplane bandwidth, also known as switching capacity, is the maximum amount of data that can be handled between the switch interface processor and the data bus, just like the total number of lanes owned by an overpass. Since the communication between all ports needs to be completed through the backplane, the bandwidth that the backplane can provide becomes a bottleneck for concurrent communication between ports.
When we buy a switch, we will see such parameters:
The greater the bandwidth, the greater the available bandwidth provided to each port, and the greater the data exchange speed; the smaller the bandwidth, the smaller the available bandwidth provided to each port, and the slower the data exchange speed. In other words, the backplane bandwidth determines the data processing capability of the switch. The higher the backplane bandwidth, the stronger the ability to process data. If you want to achieve full-duplex non-blocking transmission of the network, you must meet the minimum backplane bandwidth requirements.
The calculation formula of the backplane bandwidth is as follows:
Backplane bandwidth = number of ports × port rate × 2
Tip: For a Layer 3 switch, only the forwarding rate and backplane bandwidth meet the minimum requirements, it is a qualified switch, the two are indispensable.
- Packet forwarding rate
The data in the network is composed of data packets, and the processing of each data packet consumes resources. The forwarding rate (also called throughput) refers to the number of data packets that pass through a unit of time without packet loss. Throughput is like the traffic flow of an overpass. It is the most important parameter of a three-layer switch, and it marks the specific performance of the switch. If the throughput is too small, it will become a network bottleneck and negatively affect the transmission efficiency of the entire network.
The switch should be able to achieve wire-speed switching, that is, the switching rate reaches the data transmission speed on the transmission line, thereby eliminating the switching bottleneck to the greatest extent. For the Layer 3 core switch, if you want to achieve non-blocking transmission of the network, this rate can ≤ the nominal Layer 2 packet forwarding rate and the rate can ≤ the nominal Layer 3 packet forwarding rate, then the switch is doing Layer 2 and Layer 3 Line speed can be achieved when layer switching.
The formula for packet forwarding rate is as follows:
Throughput (Mpps) = Number of 10 Gigabit ports × 14.88 Mpps + Number of Gigabit ports × 1.488 Mpps + Number of 100 Mbit ports × 0.1488 Mpps.
If the calculated throughput is less than the throughput of your switch, then you can achieve line speed.
If there are 10 Gigabit ports and 100M ports, they will be included, and if they are not, they can be ignored.
