Lean Core vs. Hollow Core Architectures

D.

The lean core and hollow core architectures are two different models for building service provider networks. Both models have different characteristics, advantages, and drawbacks. The main difference between these architectures is how they handle the control and forwarding planes in the network.

The hollow core architecture is designed to address challenges associated with isolated packet, optical TDM, and DWDM layer control planes. The control plane is separated from the forwarding plane, and the network uses transport switching function to forward subscriber traffic instead of IP. This enables the network to scale more efficiently and handle more traffic. The hollow core model defines two models of operation: peering and overlay. In the peering model, the network uses BGP to exchange routing information between service providers. In the overlay model, the network uses MPLS tunnels to connect different parts of the network.

On the other hand, the lean core architecture adapts full IP architectures by using MPLS to forward subscriber traffic instead of IP. The network uses a mesh of circuits between each of the edge and peering nodes, which creates a dense mesh of connections. This enables the network to be more resilient and provide better traffic engineering. However, the lean core architecture ignores the challenges associated with isolated packet, optical TDM, and DWDM layer control planes, which may limit its scalability.

In summary, the main difference between the lean core and hollow core architectures is that the hollow core model uses a transport switching function and defines two models of operation (peering and overlay), whereas the lean core model adapts full IP architectures by using MPLS and creates a dense mesh of circuits between each of the edge and peering nodes.