Network operators frequently utilize service functions such as packet filtering at firewalls, load-balancing and transactional proxies (for example spam filters) in the delivery of services to end users. Delivery of these types of services is undergoing significant change with the introduction of virtualization, network overlays, and orchestration. Deploying service functions to support service delivery is currently both a technical and an organizational challenge that involves significant modification to the network configuration, impacting the speed at which services can be deployed and increasing operational costs. Such services are typically implemented by the ordered combination of a number of service functions that are deployed at different points within a network. Today, common deployment models have service functions inserted on the data-forwarding path between communicating peers. Going forward, however, there is a need to move to a different model, where service functions, whether physical or virtualized, are not required to reside on the direct data path and traffic is instead steered through required service functions, wherever they are deployed. For a given service, the abstracted view of the required service functions and the order in which they are to be applied is called a Service Function Chain (SFC). An SFC is instantiated through selection of specific service function instances on specific network nodes to form a service graph: this is called a Service Function Path (SFP). The service functions may be applied at any layer within the network protocol stack (network layer, transport layer, application layer, etc.). The SFC working group will document a new approach to service delivery and operation. It will produce an architecture for service function chaining that includes the necessary protocols or protocol extensions to convey the Service Function Chain and Service Function Path information to nodes that are involved in the implementation of service functions and Service Function Chains, as well as mechanisms for steering traffic through service functions. The WG will examine existing identifier schemes, if there is a need for such identifiers for the steering of packets to the service functions in the service chain, before defining any new identifier scheme. The working group will examine what information needs to be gathered from the network and service functions in support of Service Function Chaining and how that information may be made available to the components of the Service Function Chaining architecture. The SFC WG will closely consider and address the management and security implications when documenting these deliverables. Specifically, the SFC WG is chartered to deliver the following: 1. Problem Statement: This document will provide a summary of the problem space to be addressed by the SFC working group including example high-level use cases. Additionally, the working group will normalize nomenclature and definitions for service function chaining. 2. Architecture: This document will provide a description of the SFC architectural building blocks and their relationships including interconnection, placement of SFC specific capabilities, management, diagnostics, design analysis, and security models, as well as requirements on the protocol mechanisms. The initial scope is restricted to a single administrative domain, keeping in mind that architectural decisions made for the intra-domain case may have implications for the inter-domain case. 3. Generic SFC Encapsulation: This document will describe a single service-level data plane encapsulation format that: - indicates the sequence of service functions that make up the Service Function Chain through an identifier or by an explicit list - specifies the Service Function Path, - communicates context information between nodes that implement service functions and Service Function Chains. It is intended that the encapsulation format be agnostic to the layer at which it is applied and the service that is being constructed. That is, the same encapsulation may be used on a service function chain applied at the network layer or at any other layer, and the same encapsulation format will apply for the construction of Service Function Paths regardless of the actual service. The working group will consider using an existing encapsulation (with extensions as appropriate) if a suitable candidate is found. 4. Control Plane Mechanisms: A document will be developed to describe requirements for conveying information between control or management elements and SFC implementation points. All protocol extension work resulting from these requirements should be carried out in the working group responsible for the protocol being modified in coordination with this working group, but may be done in this working group under a revised charter after agreement with all the relevant WG chairs and responsible ADs. 5. Manageability: Work on the management and configuration of SFC components related to the support of Service Function Chaining will certainly be needed, but first needs to be better understood and scoped.