What Is SFC?
SFC is an important means for orderly service processing of traffic on an NFV network. In addition to basic network switching devices on a data center network, some value-added service (VAS) devices such as firewalls, load balancers, and intrusion prevention system (IPS) devices are deployed on the network to ensure network security protection and service scheduling. To meet the requirements of different service traffic and reduce deployment and maintenance costs of data center networks, you can use SFC to set network paths for traffic as required.
Origin of SFC
On a traditional network, VAS devices (such as firewalls, load balancers, and IPS devices) are tightly coupled with the network topology and hardware. These devices are dedicated and complex to deploy. When the network capacity is expanded or changed, the network topology needs to be re-planned, which increases network deployment and maintenance costs.
With the development of Network Functions Virtualization (NFV) technology, network functions are decoupled from the hardware, and forwarding and control planes are separated, making network control more elastic and flexible for data centers. On an NFV network, SFC plays an important role in forwarding traffic to implement network services in a specified sequence. When a service needs to be adjusted, you only need to update the SFC sequence without changing the network configuration. In this way, network services can be provisioned agilely.
SFC Architecture
Network devices play different roles in an SFC architecture based on their functions. SFC roles are as follows:
Service classifier (SC): An SC is located at the ingress of an SFC domain. After packets enter the SFC domain, the SC classifies the packets, sets service identifiers, and encapsulates the packets with service packet headers.
Service function (SF): SFs are devices that provide value-added services, such as firewalls and load balancers. Depending on network service header (NSH) encapsulation awareness, SFs are classified into NSH-aware SFs and NSH-unaware SFs. NSH-aware SFs can identify and forward NSH packets, and NSH-unaware SFs cannot identify NSH packets and discard them.
Service function forwarder (SFF): An SFF connects to an SF, identifies service flow information, and forwards packets based on SF service flow information.
SFC proxy: An SFC proxy is located between an SFF and an NSH-unaware SF associated with the SFF. It deletes or adds NSH encapsulation information to packets exchanged with the NSH-unaware SF.
For more information, see What is SFC
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