Core Switch vs. Distribution Switch vs. Access Switch: Understand Their Roles in Ethernet Networks

Ethernet networks are expanding and their designs are evolving and getting complex. The high capacity wide area networks (WAN) networks are introduced in telecommunication, business communication, industrial automation, and many other types of networking applications.

However, owing to the intricacy of such networks, periodic maintenance, troubleshooting, upgrades are performed in different phases. The networks are built in layers to ease maintenance-related issues.

Multiple layers consist of different devices integrated together. The layers of networks may consist of devices like transmitters, receivers, media converters, network switches, etc. Out of all the devices, the network switches play important role in managed Ethernet networks. The switches contribute to directing the data and are responsible for the transmission of signals to the addressed devices only.

There are different types of Enterprise switches that perform different roles in the layers of high-capacity networks. Core switches, distribution switches, and access switches are the common types of switches used in layer-based or hierarchy Ethernet networks. This white paper introduces all three types of network switches and further discusses the selection criteria of each switch.

An Overview of Hierarchy Ethernet Networks

The hierarchy Ethernet network is a three-layer integrated setup of networking devices. These networks are designed with three tiers that facilitate strategic installation, management,  and maintenance, and so on. The strategic design of a hierarchy network may comprise more than three layers, however, the base foundation of this network consists of three layers i.e.; core layer, distribution layer, and access layer.

Layers of Hierarchy Ethernet Network

The hierarchy network consists of the following layers.

1. Core Layer: The core layer is the backbone of the hierarchy network. The primary transmission and routing of data signals take place at the core layer only. It consists of network switches that perform routing and switching of the data. The devices like high-capacity transmitters are placed in this layer. A huge volume of data packets is routed through this layer. The routed data packets are carried forward to the distribution layer in the network.
2. Distribution Layer: The distribution layer is an intermediate layer. In this layer, the layer 2 switches are installed to distribute the data packets to the addressed group of access devices. The layer 2 switches prevent over-crowding of data packets in transmission links and access devices. The layer 2 switches collect the data from core switches, identify the type of data packet and the address of the access device. Further, the data packets are forwarded to the addressed group of access devices. Selective routing and switching take place at the distribution layer. Therefore, this layer plays important role in directing the data packets to correct addresses, reducing data traffic, and prevent reverse transmission of data through the transmission links.
3. Access Layer: The access layer is the layer where access devices are installed. This layer is directly connected to subnets. The information can be accessed by the user through these subnets. The access layer consists of layer 3 switches, which take routed and switched data packets from the distribution switches and then route them to the access devices in subnets. The access devices in subnets can be modems, video display units, receiver audio phones, IP-based devices, etc.

Note: The core layer is accessed by network developers, network managers, etc. Whereas, the access layer is accessed by the users by accessing the subnets. The distribution layer remains intermediate to bridge the core and access layer.

What are Core Switches?

A core switch is the network switch installed at the backbone of the layered or hierarchy network. These data switches are responsible for routing and data switching at the core layer of the network. The data routed and switched by the core switch is carried forward to the bottom layers of the network such as the distribution and access layer. This means the performance of the entire network relies on the data routed and switched by the core switch. Generally, multiple data switches are used at the core layer of a network so that a large amount of data can be routed to the layers in the hierarchy. Another reason for using multiple data switches at the core layer is to prevent the crowding of data packets. If data packets are highly crowded at distribution and access layers, the back-flow of data may cause a malfunction of the core layer. That is why a selection of high-capacity core switches is essential in hierarchy Ethernet networks.

Important Parameters of Core Switches

Owing to the importance of core switches, the quality and performance of the core network switches must be tested. To ensure that the switches can perform tasks of the core layer or collapsed core layer, the following parameters should be checked.

• Forwarding Rate: The forwarding rate is an essential parameter of core switches. As the core switches are responsible for routing and switching a high amount of data, the forwarding capacity of the switches must be high. The forwarding capacity of switches is known as the forwarding rate. This indicates the amount of data packets transmitted at any time. The core switches with a high forwarding rate are suitable for core layers. However, if the low forwarding rate is there, then multiple switches are used in a collapsed core layer.
• Quality of Service (QoS): Quality of Service (QoS) is essential in core switches. This parameter allows the strategic release of data packets. Since the networks are highly demanding and a massive amount of data passes through the core layer, the QoS enables the selective transmission of data packets. This way the forwarding of data packets is prioritized and therefore, important data transmits first and the least important data is sent at last.
• Redundancy: This factor of core switches should be considered so that abrupt failure can be prevented. Using swappable cooling fans and power supply modules with switches can help in enhancing redundancy.
• Compliance with Ethernet Protocols: Since the Ethernet networks are built over IEEE standards. The switches and other devices operate based on the version of IEEE standards. Therefore, the core switches should operate in compliance with Ethernet protocols being used for building the network.
• Compatibility with Different Networking Topologies: In intricate networks, a single core switch may not suffice. To install multiple cores switches, the core layer must be collapsed. Thus, the topology of networking may differ. The core switch should perform incompatibility with the adopted topology.  

What are Distribution Switches?

These switches are installed at the distribution layer of the hierarchy network. Generally, these are used for two-tier or three-tier hierarchy networks. These switches bridge the core layer and access layer. The main responsibility of these switches is to ensure the routing of data to correct devices in the access layer. However, the distribution layer handles maximum data traffic as the data packets are pushed through the core layer to the distribution layer. The distribution switches categorize these data packets and transmit them to specific workgroups. Strategic routing and data switching is done by distribution switches.

The distribution layer acts as an intermediate to the core and access layers. Therefore, the installation of distribution switches becomes truly essential.

Important Parameters of Distribution Switches

The following parameters are essential for a distribution switch to perform effectively in layer 2.

• Layer 3 Functional Compatibility: Although the distribution switches are layer 2 switches, the compatibility of these switches with layer 3 switches is important. As the layer 2 switches directly interact with layer 3 switches, the transmission compatibility of both layers should match.
• Link Aggregation: Chances of link failure are high between the access layer and distribution layer. Therefore, the distribution switches must offer link aggregation for quick recovery. This feature balances the distribution of traffic which results in prevention against link failure. In case of link failure, the diversion of transmission path and recovery of a failed link is done by link aggregation capabilities of the layer 2 switches.
• Security Policies: The high-capacity networks are sensitive to data theft and their party intrusions, therefore, the security measures are implemented at the second layer. As this layer bridges the core and access layer, security measures like access control list (ACL), user access authentication, etc are introduced in layer 2 switches. The switches should be compatible with security modifications.
• QoS/ Data Prioritization: Since layer 2 switches strategically forward the data, the Quality of Service (QoS) capability of these switches offers prioritization of data packets. This way although the data is forwarded to different layer 3 switches, it can be sent at different time-lapses based on priority.

What are Access Switches?

The access switches are the network switches that connect the access layer with the subnets. The subnets are integrated with access devices like routers, IP devices, control, and monitoring panels, etc. An access layer of a hierarchy network features multiple subnets to which the access switches are directly connected. The responsibility of routing and switching data to the subnets is of access switches. In the access layer, multiple access switches can be added. Since the access layer is the most accessed layer of the hierarchy network, switches must be capable of switching and routing data without and back-transmission of data. These switches are also called layer 3 switches.

Important Parameters of Access Switches

Since the access layer is the most interactive layer of the hierarchy network, the following parameters of access switches must be confirmed.

• Port Density: The port density is the number of ports on the access switches. Since access switches are directly linked to subnets and end-users networking devices, having a higher port density is an advantage. The higher the port density of each access switch is, the lower is the number of access switches used in the access layer.
• Port Speed: The access switches commonly come with 10/100/1000Mbps data transmission speed. Different networking activities require different transmission speeds. With an increase in demand for high-speed gigabit transmission, the ports of access switches should support the high-speed transmission of data to the subnet devices.
• Convenient Installation and Management: As multiple access switches are integrated into the access layer and additional switches may be required. To do the same easy installation is essential for the access switches. It makes the network easy to install and manage the networking parameters.
• Security: Chances of third-party intrusion through the access layer are high since it can be accessed easily. Therefore security protocols of these switches must be checked. Access control, IP source protection, DoS protection, etc should be implemented to access switches.
• Device Compatibility: The compatibility of layer 3 switches with end users’ devices is important for efficient data transfer.

Considering all the above-mentioned factors, core switches, distribution switches, and access switches can be chosen. However, to ensure the efficiency of the network, the quality of switches and performance parameters should be verified.

Core Switch vs. Distribution Switch vs. Access Switch: Comparison Summary

Conclusion

Complex Ethernet networks feature a hierarchy comprising multiple layers. The core layer, distribution layer (layer 2), and access layer (layer 3) are the three layers used to build hierarchy networks for industrial, domestic, and commercial data transmission. All three layers of the hierarchy network are introduced in this white paper along with the sole responsibility of each layer.  Further different types of network switches used in these networks are discussed, namely, core switches, distribution switches (layer 2 switches), and access switches (layer 3 switches). Since the selection of appropriate switches is essential to build a high redundancy network, therefore important parameters of these switches are discussed individually. To know more about these network switches, please visit https://www.versitron.com/.