Service Function Chaining
charter-ietf-sfc-00-01

Networks, servers, storage technologies, and applications, have all
undergone significant change in recent years with the introduction of
virtualization, network overlays, and orchestration. Service delivery
is currently both a technical and organizational challenge that
involves significant modification to the network configuration.
Services are typically implemented by the ordered combination of a
number of service functions that are deployed at different points
within the network. Today, a common deployment model has service
functions physically inserted on the data forwarding path between
communicating peers. Going forward, however, there is a desire to
move to a different model, where service functions are not required to
reside on the default data path and traffic is instead steered through
services, 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). Since a given
service function may be available on more than one node within a network, a Service
Function Chain is instantiated via the selection of specific service function instances
and the network nodes on which they are provided, thereby forming a service
topology: this is called a Service Function Path. The service functions may be applied
at a specific layer within the network protocol stack (network layer, application layer,
etc.).

The Service Function Chaining (SFC) working group will develop new approaches to
service delivery and deployment. It will produce a framework for service function
chaining that includes the necessary protocols or protocol extensions to convey the
service path and service path information to nodes that implement service functions,
as well as mechanisms for steering traffic through service functions. The working
group will also 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 nodes that implement the service functions.

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 WG including example high-level use cases. Additionally, the WG
will normalize nomenclature and definitions for service function chaining.

2) Architecture: This document will provide a description of the architectural building
blocks and their relationships including interconnection, placement of capabilities,
management, diagnostics, design analysis, and security models, as well as
requirements on the protocol mechanisms.

3) Generic Service Function Chaining Encapsulation: A document will describe the
single service-level data plane encapsulation format for conveying the service function
chain and the service function path, and for communicating context information
between nodes that implement service functions. It is intended that the encapsulation
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 path realized at the
network layer or at any other layer, and the same encapsulation will apply for the
construction of service function paths regardless of the actual service.

4) Control Plane Mechanisms: A set of documents will be developed to describe
requirements and protocols necessary to convey information to service function
implementation points. Where possible, existing IETF protocols will be used and
extended. All protocol extensions work should be carried out in the working groups
responsible for the protocols being modified in coordination with this working group,
but may be done in this working group after agreement with all the relevant WG chairs
and responsible ADs.

5) Manageability: This document will address the management of service function
chaining including relevant MIBs and YANG information & data modules, and service
function chaining diagnostics.