nly way to achieve very high availability for middle-box VNFs. In most cases, an individual flow will be preserved over a single path with a single-forwarding instance of the VNF. Middle box VNFs will require application-specific logic in the VNF to resolve the complexities associated with distribut- ing flows across multiple forwarding instances. The VNF design cannot simply rely on VM move- ment by means of cluster management implemented by cloud software. This is illustrated in the example of virtual provider edge (vPE) router. The vPE is a complex middle box VNF. It is widely used to provide CUG capability for many different services, implementing the VRF capability, described in Section 3.1. Enterprise VPN service, routing functions needed for mobile core and VoIP services rely heavily on vPE. 3.4.2 vPE EXAMPLE FOR VNF-SPECIFIC RESILIENCY DESIGN vPE is a compound VNF that consists of multiple instances of at least two types of VNFs that are integrated into a coordinated system. vPE forwarding and control plane functions are separated as two distinct VNFs. A single vPE instance will consist of multiple forwarding plane VNFs and at least two control plane VNFs. Forwarding plane VNF instances enable scale by distributing cus- tomer interfaces and traffic flows across multiple VMs. Such a design enables scale out by allowing small subsets of flows belonging to the entire traffic flow to be implemented on separate forwarding VNF instances. As more customers are added to the vPE, new forwarding VNF instances can be added to accommodate growth. This also provides better resiliency by reducing the "blast radius" in the event of a server failure. In order to accomplish this, the various forwarding VNF instances need to be distributed across multiple servers in the metro cluster. Customers may use single-homed or multihomed access links to connect to the network. Majority of the customers use single-homed access since access is usually a major element of the total cost of a customer's network. Buying a second access l