Service function chaining helps automate traffic flow between services in a virtual network
In order for operators to traffic steer using a sequence of multiple Network Function Virtualizations (NFVs), they must make use of a technique called service function chaining (SFC) or network service chaining, which creates a chain of connected network services. Examples include firewalls, load balancing and intrusion protection. The technique helps automate traffic flow between services in a virtual network and, by using the optimal routing path, is also optimizes the use of network resources.
Further, structuring of SFCs can be achieved with minimal latency by utilizing the flexibility of Software-Defined Networking (SDN) because it enables increased control of network functions and policy-based resource management.
The elements of a service chain
A service chain is comprised of several elements: A foundation of code called the service template; a virtual network, or an abstract connection between physical points within a network; the actual implementation of a node service, called a service instance; and finally, a service policy, or a set of rules that dictates how data traffic moves between a virtual network and service instances.
Network service chaining and network slicing
Because network operators can use service chaining to select specific pathways for traffic, and because any one of these pathways can include any combination of services to achieve the traffic’s requirements — lower latency, higher quality of service (QoS), etc. — it brings to mind one of the hottest topics related to 5G: network slicing.
5G network slicing is a feature of a cloud-native 5G network architecture that leverages the principles behind NFV and SDN, allowing for flexible, programmable converged networks wherein disparate services that would typically require parallel systems reside on a single infrastructure. In such an architecture, each network “slice” is an isolated, bespoke end-to-end network tailored to fulfill the requirements of a particular application.
Each of the services on a given network slice are interconnected by the transport network that runs through an automated service chain, and these chain links must be in the order most appropriate for the requirements of the slice and its user demand.
“To deploy and dynamically reconfigure the SFC within each Network Slice/Cloud domain, the NFV-MANO [network functions virtualization management and orchestration] components must perform a number of configurations,” wrote Monowar Hossain, unit head of transport network and microwave at Veon in a blog post. “These operations are described as adopting the Day 0/1/2 terminology, commonly used in network automation.” He goes on to described that Day 0 configurations are those related to the initial state of the VNF instance, such as the image to be used and the initial network configuration, Day 1 configurations include the sequence of operations to be performed immediately after launching the instance and Day 2 configurations relate to any additional reconfiguration made during the lifecycle of the instance.
“SFC and [n]etwork [s]licing offer opportunities for software-driven coordination of network resources to marshal them so as to best deliver the network behavior that will support the demands of the services,” he stated.
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