The Key Characteristics of the Core, the Backbone part of the networks are:
Redundancy in this module is very important.
Most of the Core Network deployments in ISP networks are based on Full Mesh or Partial Mesh.
The reason for having full mesh physical connectivity in the Core network is that full mesh connectivity provides the most optimal network traffic and the shortest path between the two locations.
But not every network can have full mesh architecture, because it is the most expensive design option.
Instead, many operators connect their Core/Backbone locations in a partial mesh model.
In the partial mesh physical connectivity model, all of the core locations are not connected to each other, instead only the Core POP locations which have high network traffic demand are connected together.
Core/Backbone provides scalability to the Service Provider networks.
Without this layer, many Aggregation layers are required to be connected to each other to provide end-to-end connectivity.
This would be too costly and so many physical links are required to be provisioned.
The Core layer reduces the number of circuit requirements between different Aggregation networks.
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