Routing And Switching Questions Long
The purpose of Quality of Service (QoS) in network communication is to ensure that different types of network traffic receive the appropriate level of service and resources based on their priority. QoS helps to manage and prioritize network traffic to meet specific requirements, such as bandwidth, latency, jitter, and packet loss, for different applications or services.
QoS prioritizes traffic by assigning different levels of priority to different types of network traffic. This prioritization is typically based on the classification of traffic into different classes or queues. The most common QoS mechanisms used to prioritize traffic include:
1. Classification: Traffic is classified into different classes based on specific criteria such as source/destination IP address, port numbers, protocol type, or application. This classification allows network devices to identify and differentiate between different types of traffic.
2. Marking: Once traffic is classified, it can be marked with a specific priority value or Differentiated Services Code Point (DSCP). These markings are added to the packet header and are used by network devices to prioritize traffic based on its assigned priority level.
3. Queuing: Network devices use queuing mechanisms to manage and prioritize traffic based on its assigned priority. Different queues are created for each priority level, and traffic is placed in the appropriate queue based on its marking or classification. Queuing mechanisms such as First-In-First-Out (FIFO), Weighted Fair Queuing (WFQ), or Priority Queuing (PQ) are used to ensure that higher priority traffic is processed before lower priority traffic.
4. Congestion Management: QoS helps to manage network congestion by implementing congestion avoidance mechanisms such as Random Early Detection (RED) or Weighted Random Early Detection (WRED). These mechanisms monitor the network traffic and drop or mark packets when congestion is detected, ensuring that higher priority traffic is protected from congestion-related issues.
5. Traffic Shaping and Policing: QoS also includes traffic shaping and policing mechanisms to control the rate of traffic flow. Traffic shaping smooths out bursts of traffic by delaying packets, while traffic policing enforces traffic rate limits. These mechanisms help to ensure that network resources are fairly allocated and prevent any single application or user from monopolizing the available bandwidth.
By implementing QoS, network administrators can prioritize critical traffic such as voice or video conferencing over less time-sensitive traffic like file downloads or web browsing. This ensures that important applications receive the necessary resources and guarantees a consistent level of service for different types of network traffic.