Network service chaining, also known as service function chaining (SFC) is a capability that uses software-defined networking (SDN) capabilities to create a service chain of connected network services (such as L4-7 like firewalls, network address translation [NAT], intrusion protection) and connects them in a virtual chain. This capability can be used by network operators to set up suites or catalogs of connected services that enable the use of a single network connection for many services, with different characteristics.
The primary advantage of network service chaining is to automate the way virtual network connections can be set up to handle traffic flows for connected services. For example, an SDN controller could take a chain of services and apply them to different traffic flows depending on the source, destination or type of traffic. The SFC capability automates what traditional network administrators do when they connect up a series of physical L4-7 devices to process incoming and outcoming network traffic, which may require a number of manual steps.
Network Service Function Chaining and Operating Efficiency
Service Chaining is being included in many SDN and network functions virtualization (NFV) use cases and deployments, including data centers (chaining together virtual or physical network functions), carrier networks (services for S/Gi-LANs), and virtual customer edge, including virtual customer premises [vCPE] deployments).
Network service chaining can be operationally beneficial by enabling automated provisioning of network applications that may have different characteristics. For example, a video or VOIP session has more demands than simple Web access. Automated network service chaining can enable these sessions to be set up and torn down dynamically, without requiring human intervention. This also helps ensure that specific applications are getting the proper network resources or characteristics (bandwidth, encryption, quality-of-service [QoS].
Another benefit of network service chaining, when used in combination with SDN, is optimizing the use of network resources and improving application performance. SDN analytics and performance tools can use the best available network resources and help negotiate around network congestion issues – all in an automated fashion.
Network Service Chaining and Service Chain Provisioning with NFV
The “chain” in service chaining represents the services that can be connected across the network using software provisioning. This is especially important in the NFV world, where new services can be instantiated as software-only, running on commodity hardware.
Network service chaining capabilities mean that a large number of virtual network functions can be connected together in an NFV environment. Because it’s done in software using virtual circuits, these connections can be set up and torn down as needed with service chain provisioning through the NFV orchestration layer.
SFC and SDN network service chaining standards are being developed in several industry groups. The Internet Engineering Task Force (IETF) is developing a service function chaining (SFC) architecture to define how network flow classification can be used to route traffic between service functions. The European Telecommunications Standards Institute (ETSI) has a service architecture that uses network forwarding graphs to route traffic between virtual network functions (VNFs) with a network service header. And the Open Networking Foundation(ONF) has proposed a software-defined networking, SDN service chaining framework using OpenFlow to direct traffic to the appropriate service functions.