A Deep Dive into Service Chaining in NFV

Introduction to Service Chaining

This article will provide a technical deep dive into service chaining in NFV, exploring the different types of service chains, the key components involved in service chaining, and the challenges that need to be addressed.

Types of Service Chains

There are two main types of service chains:

Static Service Chains: Static service chains are pre-defined and they do not change. They are typically used for services that have a fixed set of requirements.
Dynamic Service Chains: Dynamic service chains are created on demand and they can be changed at any time. They are typically used for services that have a dynamic set of requirements.

Key Components of Service Chaining

The key components of service chaining in the ETSI NFV architecture are:

Network Service Descriptor (NSD): The NSD is a template that is used to describe a network service. It contains information about the VNFs that are part of the service, the order in which they should be chained together, and the policies that should be applied to the service.
VNF Forwarding Graph (VNFFG): The VNFFG is a graph that describes the flow of traffic through a service chain. It is made up of a number of nodes, each of which represents a VNF, and a number of links, each of which represents a connection between two VNFs.
NFV Orchestrator (NFVO): The NFVO is responsible for orchestrating the service chain. It is responsible for instantiating the VNFs, for creating the VNFFG, and for steering the traffic through the service chain.

Service Chaining Mechanisms

There are a number of different mechanisms that can be used to steer traffic through a service chain, including:

Policy-Based Routing (PBR): PBR is a technique that can be used to steer traffic based on a set of policies. The policies can be based on a variety of factors, such as the source and destination IP addresses, the TCP/UDP port numbers, and the application protocol.
Software-Defined Networking (SDN): SDN can be used to steer traffic through a service chain by programming the forwarding plane of the network devices.
Network Service Header (NSH): NSH is a new protocol that has been developed specifically for service chaining. It is a metadata header that is added to packets as they are steered through a service chain. The NSH header contains information about the service chain, such as the service path and the service index.

Challenges of Service Chaining

There are a number of challenges that need to be addressed in service chaining, including:

Interoperability: There is a need for interoperability between the different components of the NFV architecture. This is especially true for the interfaces between the NFVO, the VNFM, and the VIM.
Complexity: Service chaining is a complex process. There is a need for tools and automation to help to manage this complexity.
Performance: There is a need to ensure that service chains can meet the performance requirements of the applications. This includes things like latency, jitter, and packet loss.
Security: There is a need to ensure the security of service chains. This includes things like securing the communication between the different components of the NFV architecture and securing the VNFs themselves.

Conclusion

Service chaining is a key concept in Network Function Virtualization (NFV). It is the process of steering traffic through a sequence of Virtualized Network Functions (VNFs) to create a network service. The ETSI NFV architecture defines a number of key components and mechanisms for service chaining. There are a number of challenges that need to be addressed in service chaining, but the benefits of NFV are clear. As NFV continues to gain traction in the networking industry, the importance of service chaining will only continue to grow.