 appropriate. It keeps track of failed VNFs and distributes requests only to in-service VNFs. It marks an entire VNF cluster to be out of service when a preconfigured number of VMs in the VNF cluster fail. It supports dynamic binding for new dynamically instantiated VNFs that it needs to add to its distribution list. There can be multiple instantiations of this service if needed that may be customized to the needs of the network functions that it sends requests to. Each instantiation will need to maintain the availability state of the network functions that it monitors. 3. DNS as a service (DNSaaS): The DNS service supports address resolution and performs translation of domain names to numeric IP addresses. It must be ubiquitously deployed within the cloud infrastructure. Name resolution requests are directed to the nearest loca- tion based on the source IP to minimize latency for certain scenarios. The DNS service must support a localized DNS view, that is, a request from a network function should resolve to the local network function. It provides APIs to create and manage name resolution (DNS) records. For example, a DNS record can be created using the APIs when a new VM is cre- ated. It supports split-horizon DNS entries by providing a domain name for every instance that is launched. This domain name should resolve to the private IP address of the VM instance if queried from within the same availability region, and to the public IP address if queried from outside the cloud infrastructure or from another cloud availability region. 4. State persistence service: The state persistence service provides persistence of state in the cloud for components that are stateful. It supports the architectural trend of stateless appli- cations in a cloud and enables network functions to focus on logic. It supports replication of state across all or a subset of cloud availability regions. It supports a highly scalable cache for quick access to state information. 5. vTaps as a service: The vTaps service will provide a common way