Quality of Service is the classification and prioritization of network traffic to provide differentiated service levels.
Quality of Service (QoS) classifies and prioritizes network traffic so important traffic receives differentiated service. It is especially useful for delay-sensitive voice and video traffic. section 7.1.3
In an IPv4 packet:
The 6-bit Differentiated Services Code Point (DSCP) field supports traffic prioritization. section 7.1.3
The 2-bit Explicit Congestion Notification (ECN) field accompanies DSCP; together they replaced the older Type of Service terminology. section 7.1.3
A practical example is prioritizing a Zoom voice or video call to reduce delay and poor call quality. section 7.1.3
How Acing the CCNA Exam: Volume 1 Fundamentals and Protocols covers it
How deep it goes
Defines DSCP and ECN in the IPv4 header, but stops short of configuration or implementation procedures.
Examples
Uses Zoom calls and other voice or video traffic to illustrate delay-sensitive service.
What it assumes
Builds on recognizing IPv4 headers and their fields, especially DSCP and ECN.
What you can do after
Evaluate how DSCP and ECN support prioritization of delay-sensitive IPv4 traffic.
How it connects
Connects IPv4 headers with DSCP, ECN, voice traffic, and video traffic.
markinghas part · Marking is the process of setting packet or traffic header fields to encode classification information for network policy enforcement.
classifierhas part · A classifier is a predictive computational model that assigns inputs to one or more discrete classes or categories.
differentiated services code pointuses · The Differentiated Services Code Point is a six-bit field in an IP header that identifies a packet’s desired forwarding treatment.
meanaddresses · A mean is a measure of central tendency, calculated as the arithmetic average of values or, for a random variable, as the probability-weighted average of its possible values.
class-based weighted fair queuinguses · Class-Based Weighted Fair Queuing is a packet-scheduling technique that assigns traffic classes to queues and guarantees each queue a configured minimum share of bandwidth during congestion.
low latency queuinguses · Low Latency Queuing is a QoS scheduling technique that gives selected traffic strict priority treatment while providing bandwidth allocation for other classes.
This explainer was generated by Manning's knowledge graph from the text of Acing the CCNA Exam: Volume 1 Fundamentals and Protocols. The section links point to the parts of the book it draws on.
