FAR (Forwarding Action Rule)

Forwarding Action Rule (FAR) is a fundamental component of Software Defined Networking (SDN) that enables efficient and flexible packet forwarding in a network. In this article, we will explain what FAR is, how it works, and why it is essential for SDN.

Overview of Forwarding Action Rule (FAR)

A Forwarding Action Rule (FAR) is a set of instructions that defines how a network switch should process a packet. It maps a packet's attributes to a specific action, such as forwarding, dropping, or modifying the packet. FARs are implemented in the forwarding plane of an SDN switch, which is responsible for processing packets as they arrive at the switch and determining how to forward them.

In an SDN architecture, the control plane is separated from the forwarding plane, enabling network administrators to manage network traffic centrally and flexibly. The control plane is responsible for defining the network policies and configuring the forwarding rules for each switch. The forwarding plane, on the other hand, is responsible for executing the policies and rules defined in the control plane.

How does Forwarding Action Rule (FAR) work?

When a packet arrives at an SDN switch, it is processed by the switch's forwarding plane. The switch first examines the packet's header to determine its source and destination addresses, as well as other attributes such as the packet's protocol, port numbers, and Quality of Service (QoS) requirements.

The switch then consults the Forwarding Action Rules (FARs) that have been configured in the switch's forwarding table. The forwarding table is a lookup table that maps packet attributes to specific forwarding actions. Each entry in the forwarding table is called a forwarding rule or a forwarding entry.

The forwarding rule consists of two parts: a match field and an action field. The match field specifies the packet attributes that the forwarding rule should match, such as the packet's source and destination addresses or the packet's protocol. The action field specifies the forwarding action that should be taken if the packet matches the forwarding rule. The forwarding action can be to forward the packet to a specific port, drop the packet, or modify the packet's attributes.

When a packet arrives at a switch, the switch matches the packet's attributes against the forwarding rules in the forwarding table. If there is a match, the switch performs the action specified in the forwarding rule. If there is no match, the switch forwards the packet to the controller, which can then install a new forwarding rule in the switch's forwarding table.

Why is Forwarding Action Rule (FAR) essential for SDN?

Forwarding Action Rule (FAR) is an essential component of SDN because it enables flexible and efficient packet forwarding in a network. Here are some of the key benefits of FAR in SDN:

1. Flexibility: With FAR, network administrators can define network policies and forwarding rules centrally and flexibly. This enables network administrators to respond quickly to changing network conditions and traffic patterns. For example, if a network administrator wants to prioritize traffic from a particular application, they can configure a forwarding rule to give that traffic higher priority.
2. Scalability: In traditional networks, forwarding decisions are made by the switch itself, which can lead to scalability issues when the network grows. With SDN and FAR, forwarding decisions are made by the controller, enabling network administrators to manage large and complex networks more efficiently.
3. Programmability: With FAR, network administrators can write scripts or programs to automate network management tasks. For example, a network administrator can write a script to automatically configure a new switch when it is added to the network.
4. Troubleshooting: With FAR, network administrators can easily troubleshoot network issues by examining the forwarding rules in the forwarding table. For example, if a packet is not being forwarded as expected, the network administrator can examine the forwarding rules in the forwarding table to identify any misconfigured rules or missing rules.
5. Customization: With FAR, network administrators can customize the forwarding behavior of switches to suit their specific needs. For example, they can configure switches to forward packets based on specific packet attributes, such as the source or destination IP address, or based on specific QoS requirements.

Conclusion

Forwarding Action Rule (FAR) is a fundamental component of Software Defined Networking (SDN) that enables efficient and flexible packet forwarding in a network. FAR enables network administrators to define network policies and forwarding rules centrally and flexibly, automate network management tasks, troubleshoot network issues, and customize the forwarding behavior of switches. With FAR, SDN networks are more scalable, flexible, programmable, and customizable, making them well-suited for today's dynamic and evolving network environments.