How do you optimize the use of diffserv code points (DSCP) for different traffic classes in your network?

1 What are DSCP values and how do they work?

DSCP stands for differentiated services code point. It is a 6-bit field in the IP header that indicates the level of service that a packet should receive. DSCP values can range from 0 to 63, and they are divided into several classes and drop probabilities. Each class represents a type of traffic, such as voice, video, or data, and each drop probability indicates how likely a packet is to be dropped or delayed when congestion occurs. By using DSCP values, you can assign different QoS policies to different traffic classes in your network.

2 How do you identify traffic classes in your network?

Before you can mark and manage traffic classes using DSCP, you need to identify what types of traffic are flowing in your network and what are their QoS requirements. You can use various tools and methods to analyze your network traffic, such as network monitoring software, flow analysis, packet capture, or application discovery. You should also consult with your application vendors, users, and business stakeholders to understand the performance and availability expectations for each application. Based on your analysis, you can define your traffic classes and their QoS objectives.

3 How do you mark traffic classes using DSCP?

Once you have identified your traffic classes, you need to mark them with the appropriate DSCP values. You can mark traffic at the source, such as the application server, the user device, or the edge router, or at any intermediate point in the network, such as a switch or a firewall. The best practice is to mark traffic as close to the source as possible, to avoid inconsistent or conflicting markings along the path. You can use various mechanisms to mark traffic, such as network-based application recognition (NBAR), class-based marking (CBM), or policy-based marking (PBM).

4 How do you manage traffic classes using DSCP?

After you have marked your traffic classes with DSCP values, you need to manage them according to their QoS policies. You can use various techniques to manage traffic, such as classification, queuing, scheduling, shaping, policing, or dropping. The most common technique is to use class-based weighted fair queuing (CBWFQ), which allocates bandwidth and buffer space to different queues based on their DSCP values and weights. You can also use low latency queuing (LLQ) to provide strict priority to the most critical traffic classes, such as voice or video.

5 What are the benefits and challenges of using DSCP for QoS?

Using DSCP for QoS can provide several benefits for your network, such as improved application performance, reduced network congestion and packet loss, enhanced security and compliance, increased efficiency and scalability, and simplified network management and troubleshooting. However, using DSCP for QoS also poses some challenges, such as complexity and overhead of marking and managing traffic, compatibility and interoperability issues with different devices and vendors, trust and security risks of relying on external markings, and potential conflicts and trade-offs between different traffic classes and QoS policies.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?