What is VNFFGD Virtual Network Function Forwarding Graph Descriptor

VNFFGD (Virtual Network Function Forwarding Graph Descriptor): Orchestrating Traffic Flow in NFV

In Network Functions Virtualization (NFV), a VNFFGD (Virtual Network Function Forwarding Graph Descriptor) plays a vital role in managing traffic flow through Virtual Network Functions (VNFs). It acts as a blueprint that defines the sequence and path for network traffic within a service chain. Here's a detailed technical explanation:

Understanding NFV and VNFs:

• Network Functions Virtualization (NFV): This technology virtualizes network functions traditionally performed by dedicated hardware appliances. Virtual Network Functions (VNFs) are software applications that deliver these functionalities, running on standard server hardware.
• VNF Chaining: Network services often require multiple VNFs working together in a specific order. VNF chaining refers to the process of connecting VNFs to create a service path for traffic to traverse.

VNFFGD Explained:

The VNFFGD acts as a map or blueprint for traffic flow within an NFV service chain. It provides details on:

• The VNFs involved: Specifies the specific VNFs that need to be deployed and chained together to deliver the network service.
• The order of execution: Defines the sequence in which traffic needs to pass through the VNFs in the chain.
• The connections between VNFs: Outlines the logical links that connect the VNFs, indicating the data flow path.
• Traffic forwarding rules (Optional): May specify conditions or filters to determine which traffic should be directed through the VNF chain. This allows for selective traffic processing based on specific criteria.

Benefits of VNFFGDs:

• Clarity and Visibility: VNFFGDs provide a clear visual representation of the service chain, simplifying network design, deployment, and management. Operators can easily understand the traffic flow path through the VNFs.
• Dynamic Orchestration: VNFFGDs enable dynamic VNF chaining. New service chains can be created or existing ones modified based on network traffic demands. This allows for flexible service provisioning and resource optimization.
• Policy Enforcement: Traffic forwarding rules within VNFFGDs can be used to enforce specific policies on the traffic traversing the chain. For example, certain traffic types might be directed through specific VNFs for filtering or security purposes.
• Standardized Service Delivery: VNFFGDs promote standardized service delivery across different NFV platforms. They describe the service chain independent of the underlying infrastructure, facilitating portability and interoperability.

Technical Considerations for VNFFGDs:

• Format: VNFFGDs are typically described using standardized formats like TOSCA (Topology and Orchestration Specification for Cloud Applications). TOSCA offers a vendor-neutral way to define service chains, ensuring interoperability with different NFV Management and Orchestration (MANO) frameworks.
• Deployment and Management: VNFFGDs are used by NFV orchestrators to deploy and manage service chains. The orchestrator translates the VNFFGD into specific instructions for deploying and configuring the VNFs, as well as establishing the connections between them.
• Relationship with VNFD: VNFFGDs are distinct from, but complementary to, VNFDs (Virtual Network Function Descriptors). VNFDs describe individual VNFs, while VNFFGDs depict how these VNFs are chained together to form a service path.

VNFFGD vs. VNF Forwarding Graph (VNFFG):

These terms are sometimes used interchangeably, but there's a subtle difference. VNFFG refers to the conceptual representation of the service chain, while VNFFGD is the formal descriptor that captures this information in a standardized format for use by NFV orchestrators. Think of VNFFG as the "what" and VNFFGD as the "how."

VNFFGD and Orchestration Lifecycle:

1. VNFFGD Creation: Network operators or service providers define the service chain using a VNFFGD, specifying the VNFs, order, and connections.
2. VNFFGD Validation: The VNFFGD is validated for syntax and semantic correctness to ensure it can be successfully processed by the NFV orchestrator.
3. Service Chain Orchestration: The NFV orchestrator utilizes the VNFFGD to deploy the service chain. This involves deploying the individual VNFs, establishing the connections between them, and configuring the traffic flow based on the defined rules.
4. Service Chain Management: The VNFFGD can be used for ongoing management of the service chain, such as scaling VNFs or modifying traffic forwarding rules based on changing network conditions.

Conclusion:

VNFFGDs are essential elements for defining and orchestrating traffic flow in NFV deployments. They provide a standardized way to describe service chains, enabling efficient and dynamic service delivery.