In many network constructions, we have all heard of switches. So do you really understand switches? Why are aggregation switches often overlooked? What is an aggregation switch? From our perspective, let’s share everything we know about aggregation switches.
Definition of Network Hierarchy
In conventional network construction, we divide the switches into a hierarchical structure according to the number of connected network devices. Typically, we have three structural levels: access, aggregation, and core. In layman’s terms, network level construction is similar to the construction of a company. The access layer is like the employees at the bottom of the company, the distribution layer is the project manager or director of the company, and the core is the CEO. A reasonable network hierarchy, like a mature enterprise, can efficiently process, analyze and upload data and information.
This is also a cost-reduction solution. With a flat layered network design, this makes it difficult for switches to filter out unwanted traffic, and it makes it difficult to control broadcasts. Therefore, the larger the scale of the network, the more the network layered design is required.
The role of aggregation switches
As we just mentioned, the aggregation switch is like the project manager or director within the company. They need to process the information that aggregates the base layer (access layer switches) and filter them and upload this to the CEO (core layer switches).
Usually, when the distribution layer switch receives data from the access layer switch, it will perform local routing, filtering, traffic balancing, and QoS priority management; then, it will perform security mechanisms, IP address translation, and multicast management. and other processing; finally, forward the data to the core layer switch or perform local routing processing according to the processing result to ensure the normal operation of the core layer.
As can be seen from the above, the distribution layer switch has functions such as source address, destination address filtering, real-time policy, and security, as well as network isolation and segmentation. Compared with access switches, distribution layer switches have better performance and higher switching speeds.
However, in practical applications, some network architectures only have access layer switches and core switches without distribution layer switches. This is because the network is small, simple, and has a short transmission distance. In order to reduce network costs and maintenance burdens, users do not deploy aggregation switches. However, if the number of network users exceeds 200, and the number of users will continue to grow in the future, it is recommended to deploy a distribution layer switch.
What factors should be considered when choosing a distribution layer switch?
Since the vast majority of networks will deploy distribution layer switches, what factors should be considered when choosing a distribution layer switch? You can start from the following aspects:
Backplane Bandwidth and Packet Forwarding Rate
As we all know, backplane bandwidth and packet forwarding rate are important factors to measure the ability of a switch to forward packets. If the backplane bandwidth and packet forwarding rate are small, the data processing capability of the switch will be weaker. If the line speed cannot be reached, it is easy to cause data congestion.
However, most of the switches on the market can achieve wire-speed switching. Therefore, when selecting the distribution layer switch, you can choose the appropriate one according to the actual needs. Do not choose the lower one, nor do you need to choose the higher one, to avoid waste of resources.
Port type and number of ports
Because the distribution layer switch needs to aggregate the data of multiple access switches and forward it to the core switch, when selecting the distribution layer switch, it is necessary to consider the upstream port type and port number of the access switch in the network, as well as the downstream ports of the core switch. type.
For example, when the distribution layer switch needs to be connected to an access switch with SFP optical ports, a distribution layer switch with SFP optical ports on the downlink port is selected. The specific port number depends on the number of access layer switches to be connected. , such as 24-port, 48-port distribution layer switches.
In addition, with the continuous development of network communication technology, the network scale will become larger and larger, so it is best to consider the scalability of the switch port when selecting a distribution layer switch, and try to choose an enterprise-class switch with scalable ports as the distribution layer switch.
Port rate
The selection of the port rate of the distribution layer switch also takes the uplink and downlink into consideration. The port rate can be the same or different. For example, the uplink and downlink are gigabits, or the downlink is gigabit, and the uplink is 10G. The specific rate depends on the uplink port rate of the access layer switch and the downlink port of the core layer switch rate.
Function management
Unlike the core layer switch, the distribution layer switch can choose either a layer 2 switch or a layer 3 switch as the distribution layer switch. When the Layer 2 switch is selected as the distribution layer switch, the routing and management strategy must be completed by the core switch. However, some commonly used network management functions are necessary, such as link aggregation, QoS, VLAN, ACL, etc.
Link aggregation
Since the distribution layer switch needs to receive traffic sent by multiple access switches and forward all traffic to the core switch as quickly as possible (that is, the aggregation switch needs a high-bandwidth aggregation link connecting the core switch), the aggregation switch needs to Link aggregation is supported to ensure that the access layer is provided with sufficient bandwidth and can continue to work when one of the links is disconnected.
QoS
Because most users now access video, voice, and other devices at the access layer, which leads to a variety of traffic types in the LAN, the QoS priority policy can give priority to the specified traffic (such as voice, video, etc.) to ensure its service. quality. Therefore, you need to choose an enterprise-level switch that supports QoS as an aggregation switch when purchasing, otherwise, the performance and quality of voice and video communications will not be guaranteed during network transmission.
Security strategy
In order to prevent illegal intrusion, snooping, and bad information or other network devices from accessing the network, the aggregation switch can choose enterprise-level switches that support security policies, such as ACL (Access Control List), which can identify the types of allowed communication traffic and effectively block specific types of traffic. Traffic (referring to undesired traffic) is transmitted to ensure network security.
Data redundancy
Redundancy is the guarantee of network security and one of the important factors to consider when selecting aggregation switches. For aggregation switches, power redundancy is very important, because when a power supply of the aggregation switch fails or needs to be replaced, the aggregation switch can still rely on another power supply to continue working without affecting the normal operation of the network.
Summarize
After the detailed introduction in this article, I believe that you have a better understanding of aggregation switches and can make the right choice when purchasing. As we all know, access switches and core switches are indispensable devices in the three-layer network architecture, so their selection is also particularly important.
