Best Service for Enterprise Customers with Few Sites and Many Prefixes

A.

When an enterprise has few sites but a large number of prefixes, the service provider should offer L3 VPNs (Layer 3 Virtual Private Networks) based on RFC 2547. This is because L3 VPNs provide a scalable and efficient way to connect the customer's sites and maintain the privacy and security of their traffic.

L3 VPNs use a virtual routing and forwarding (VRF) table to keep the customer's traffic separate from other customers' traffic on the provider's network. Each VRF table contains the customer's routes and is associated with a specific VPN. This allows the service provider to offer multiple VPNs to different customers, while keeping each customer's traffic isolated from the others.

In addition, L3 VPNs use BGP (Border Gateway Protocol) to exchange routing information between the customer's sites and the provider's network. This allows for efficient routing of the customer's traffic across the provider's network, while also allowing the service provider to implement policies to control the traffic.

Compared to VPWS (Virtual Private Wire Service) and VPLS (Virtual Private LAN Service), L3 VPNs are more efficient in terms of forwarding memory, routing memory, and CPU resources. This is because VPWS and VPLS are based on Layer 2 technologies and require the provider to maintain a full mesh of connections between the customer's sites, which can be inefficient and difficult to scale.

InterAS L3 VPN (Inter-Autonomous System L3 VPN) is a type of L3 VPN that allows for VPN connectivity between different service providers. This may not be necessary for enterprise customers with only a few sites, so L3 VPNs based on RFC 2547 would be the most appropriate choice for the given scenario.