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Flow routing

Flow routing definition

Flow routing in network computing is a technique used for managing how packets travel between nodes in a network. Rather than routing each one individually, packets are grouped into “flows” based on certain characteristics, and each flow is routed as a single unit. These characteristics can include the source and destination IP addresses and ports or the protocol in use.

See also: data transmission, node, internet routing

How flow routing works

Flow routing begins by identifying the packets that form a flow. The criteria for defining a flow can vary depending on the specific needs of the network. Typical examples include source and destination addresses and port numbers. Once a flow has been defined, routing decisions apply to its entirety rather than to each packet. The flow is then directed along a chosen path through the network.

The benefits of flow routing are best seen in a network designed with flow-based principles in mind. In some traditional network designs, implementing flow routing may require significant changes to network infrastructure or management techniques.

Flow routing types

  • TCP/IP flow routing. In TCP/IP networks, flows are often defined by the TCP or UDP port numbers, along with the source and destination IP addresses. A particular path is assigned for a flow, and all packets within that flow follow the same route.
  • SDN flow routing. In software-defined networks (SDN), flow routing can be managed programmatically. The SDN controller, a software entity that manages all network decisions, can define flows and control their paths based on various parameters.

Flow routing advantages

  • Improved network efficiency. Flow routing reduces processing overhead, as routing decisions apply to the entire flow rather than to each packet. This can lead to overall improved performance and efficiency of the network.
  • Quality of service (QoS) management. Because a flow represents a series of packets from a single session, certain types of data can be prioritized over others. For instance, a flow consisting of video streaming or VoIP data can get priority. That would reduce jitter and latency and improve the quality of the service.
  • Reduced network congestion. Managing traffic at the flow level allows to reduce congestion by adjusting the flow path based on current network conditions, such as congestion, link failure, or network load.
  • Enhanced security. Flow-based routing can strengthen network security by allowing for the monitoring of specific flows for malicious activity. It can also provide more granular network access control, allowing for blocking or permitting certain types of traffic (or flows) as needed.
  • Predictability. Flow routing ensures all packets of a flow follow the same path, providing predictability. This is crucial for some types of applications, like real-time video or audio streams, which are sensitive to changes in delay.
  • Scalability. Flow routing is highly scalable, making it an effective choice for large networks or those with high traffic variability. As network demands grow, flow routing can adapt by creating new flows or adjusting the paths of existing ones.