Hierarchical Design Model

In this article we will discuss Hierarchical Design Model, will make brief discussion on Hierarchical Design Model, In last article we discuss about The Need to Scale the Network.

The campus wired LAN uses a hierarchical design model to break the design up into modular groups or layers. Breaking the design up into layers allows each layer to implement specific functions.

Which simplifies the network design and therefore the deployment and management of the network.

The campus wired LAN enables communications between devices in a building or group of building, as well as interconnection to the WAN and internet edge at the network core.

A hierarchical LAN design includes the following three layers, as shown in Figure 1:

  • Access layer
  • Distribution layer
  • Core layer

Each layer is designed to meet specific functions.

The access layer provides endpoints and users direct access to the network. The distribution layer aggregates access layers and provides connectivity to services. Finally, the core layer provides connectivity between distribution layers for large LAN environments. User traffic is initiated at the access layer and passes through the other layers if the functionality of those layers is required.

Even though the hierarchical model has three layers, some smaller enterprise networks may implement a two-tier hierarchical design. In a two-tier hierarchical design, the core and distribution layers are collapsed into one layer, reducing cost and complexity, as shown in Figure 2.

In flat or meshed network architectures, changes tend to affect a large number of systems. Hierarchical design helps constrain operational changes to a subset of the network, which makes it easy to manage as well as improve resiliency. Modular structuring of the network into small, easy-to-understand elements also facilitates resiliency via improved fault isolation.

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