What are different packet scheduling techniques used by routers?

Packet switching uses scheduling techniques to manage the transmission of packets over a network.

Learn more about packet switching.

Packet scheduling techniques are employed within routers as part of the packet switching process to determine the order and priority of packet transmission.

Some scheduling techniques are as follows:

• First in, first out (FIFO) scheduling

• Weighted fair queuing (WFQ)

• Priority queuing

FIFO operates on the principle that packets are transmitted in the order they arrive at the router. In other words, the packet that arrives first is processed and transmitted first.

It is a queuing approach in which the router processes the packets one by one in the order they enter the queue.

How FIFO works

The router places incoming packets in a queue upon their arrival. The router follows a sequential approach and process and transmit the packets in the exact order they enter the queue. FIFO scheduling maintains a fair and linear delivery order by serving packets in the same sequence they arrive.

Real-world example

A web server receives requests from multiple clients. When more than one client requests a web server, FIFO scheduling processes incoming packets. The server's network interface queues the incoming requests, and the FIFO scheduler processes them in the order they arrive, ensuring the service of each client's request fairly and timely.

Priority queuing (PQ)

It allows network administrators to assign different priority levels to packets based on their importance or quality of service (QoS)Technology that manages data traffic to reduce packet loss and latency on a network. .

By classifying packets into different priority queues, PQ ensures that high-priority packets receive preferential treatment over lower-priority traffic during network congestionIt occurs when the traffic flowing through a network exceeds its maximum capacity. or resource limitations.

How PQ works

The priority queuing scheduler processes packets based on their assigned priority levels. Higher-priority queues are given priority over lower-priority queues during the packet transmission process, ensuring that packets with higher priorities are serviced first and experience minimal delays.

Real-world example

Voice over IP (VoIP) enables voice communication over IP networks. Priority queuing prioritizes voice packets over other traffic types. Voice packets are prioritized and placed in a separate queue during network congestion to ensure minimal delays and maintain call quality.

Weighted fair queuing (WFQ)

Weighted fair qieuing is a method for scheduling packets that provide fairness and prioritize network traffic management. It assigns weights to different flows or applications to treat them differently based on their priorities and bandwidth needs.

How WFQ works

In WFQ, incoming packets are classified into queues and weights are assigned to queues based on their priority, for instance, the queue with highest priority has the highest weight. The router serves as the queue's round-robin. Queues with higher weights receive more transmission opportunities, allowing them to transmit more packets and experience reduced queuing delays. This approach ensures preferential treatment for critical or high-priority traffic while maintaining fairness among all queues.

In the illustration above, there are three queues: the first queue Q1 with weight 4 (high priority), the second queue Q2 with weight 3 (medium priority), and the third queue Q3 with weight 2 (low priority). Queues are processed and router selects the number of packets from each queue based on their corresponding weights. Router selects four packets from Q1, then three packets from Q2, and then two packets from Q3. The cycle repeats.

Real-world example

WFQ scheduling prioritizes real-time video and audio streams in a video conferencing application to facilitate seamless communication. WFQ ensures timely delivery and guarantees a smooth conference experience by assigning higher weights to these flows. Other data flows like file transfers and web browsing are given lower weights to maintain fairness.