3.1.Network Hierarchy

1. Flat Switched Network

• Hubs and switches were added as more devices needed to be connected.

• A flat network design provided little opportunity to control broadcasts or to filter undesirable traffic.

• As more devices and applications were added to a flat network, response times degraded, making the network unusable.

• Early networks were deployed in a flat topology as shown in Figure below.

2. Hierarchical Network

• A hierarchical network design involves dividing the network into discrete layers.

• Each layer, or tier, in the hierarchy provides specific functions that define its role within the overall network.

• This helps the network designer and architect to optimize and select the right network hardware, software, and features to perform specific roles for that network layer.

• Hierarchical models apply to both LAN and WAN design.

• A typical enterprise hierarchical LAN campus network design includes the following three layers:

  1. Access layer: Provides workgroup/user access to the network

  2. Distribution layer: Provides policy-based connectivity and controls the boundary between the access and core layers

  3. Core layer: Provides fast transport between distribution switches within the enterprise campus

3. Multi Building Enterprise Network Design

• Another sample three-layer hierarchical network design is displayed in Figure below.

• Notice that each building is using the same hierarchical network model that includes the access, distribution, and core layers.