How to choose a switch? How to determine the network structure according to the project? We have such questions in most of the projects we do. Here are the six indispensable tips when you choose a switch in a project.

NETWORK SCALE AND LAYER

You can choose the switch according to the network scale and network layer that the switch is working. The network scales generally are small and medium-scale networks and medium and large-scale networks.

How to plan the network layer

Network structure determines what equipment to use. There are only core layer and access layer in some small-scale networks, and network pressure is not too much, therefore, you can choose the layer 2 managed switches as the core switches, for example, in a small-scale surveillance network that the data is only transferring in the intranet.

Of course, in large-scale networks, you need a three-layer structure (access, aggregation, core) to break down the pressure of the core switch. It may involve the function of VLAN division, network management, etc., then the layer 3 switches are recommended.

You may doubt if it needs to set up a four-layer structure. Most network structures are only three layers, the fewer the layers of the network structure, the faster the network responses. A simple network structure benefits both response time and post-failure maintenance.

PORT NUMBERS OF THE SWITCH

The number of physical ports supported by the switch determines the number of terminals or secondary receiving devices accessed by this switch and needs to be selected according to actual needs. Of course, It also needs to consider network expansion of the future. The access ports of the switch are used to connect to intranet terminals, and the uplink ports are used to connect to higher-layer devices.

PORT PARAMETERS

Port parameters mainly need to be considered include

- Port rate (100M, Gigabit, 10 Gigabit)

- Port type (RJ45 port, SFP port, PoE RJ45 port, etc.)

How many fiber ports, or how many Ethernet ports, etc., the number of 100M ports and gigabit ports.

FUNCTION OF THE SWITCH

It needs to consider if the switch supports functions including management function, module redundancy, routing redundancy, Layer 4 switching, scalability, as well as security features, etc. Specifically, such as access control, 802.1X authentication, loopback detection, IP-VLAN-MAC-Port bind, IGMP snooping, etc.

BACKPLANE BANDWIDTH

The backplane bandwidth is also known as switching capacity, which is the maximum amount of data that can be throughput between the processor of the switch port and the data bus, which is like the sum of the lanes owned by the overpass. Since all inter-port communication needs to be done through the backplane, the bandwidth that the backplane can provide becomes the bottleneck when there is concurrent communication between ports.

PACKET FORWARDING RATE

Data in a network is composed of individual packets, and the processing of each packet consumes resources. Forwarding rate (also called throughput) is the number of packets that pass through per unit time without packet loss. Throughput is like the traffic flow on an overpass and is one of the most important parameters of a Layer 3 switch, signaling the specific performance of the switch. If the throughput is too small, it can become a network bottleneck and negatively affect the transmission efficiency of the entire network.

The switch should be able to achieve wire-speed switching, where the switching rate reaches the data transfer rate on the transmission line, thus maximizing the elimination of switching bottlenecks. For Layer 3 core switches, if you want to achieve non-blocking transmission in the network, the requirement should be following

Actual rate energy ≤ Nominal Layer 2 packet forwarding rate and the rate energy≤ Nominal Layer 3 packet forwarding rate. Then the switch can achieve wire speed when doing Layer 2 and Layer 3 switching.