port ports is specified by the service path for each service and connectivity between the transport ports where these service paths are generated from a data model expressing the relationships between a service component, services, and service paths; and are propagated/ applied from a management system to the service instances (through a yet-to-be- determined API). Downloaded 4/15/2022 9:44:49 AM Nova Southeastern University IP Address: 137.52.76.29 Virtualizing Network Functions in Software-Defined Networks Such approach to chaining via a series of familiar application-keyed technologies viz. DNS and ADC/LB along with some new application management technologies viz. controllers and their API may become interesting if the number of chains (and thus, tunnels) becomes overwhelming. Alternatively, the functional elements on the same device might use IPC mechanisms via shared memory to improve performance in cases where a mixture of application interaction via an external protocol and internal IPC form the chain. Scalability One cannot ignore the consideration around the scale and complexity even if the current state of SDN makes the network construct acceptable, given that it is already an available entity with which one can experiment and build. However, scale and complexity also cannot drive the application-level approach conversation. Placement of the service nodes and constraints that may restrict the service paths are the major components which the complexity discussion revolves around - How many chains will there be, and what are the constraints on the path selection of service chains (e.g., overall latency of the delivered service, administrative boundaries, and tariffs)? How do those constraints affect the HA policy for a service (e.g., should individual SETs be added to or from the chain if their placement causes trombone flows in the network, or should the flow fail over to an entirely new chain)? Figure 10. Application Level Networking via NFV Host Kernel TCP Virtual Appliance Based Service Host Kernel T