QoS Traffic
Generator.
Precision network validation for DSCP, path MTU awareness, and packet-level throughput evidence.
QoS Traffic Generator
Precision Network Validation
Automated QoS stream generation, DSCP coverage, and evidence compilation designed for service provider test workflows.
Pre-Flight Diagnostics
The QoS Traffic Generator begins with rapid path discovery and health checks. Before any stress traffic is launched, it validates RTT, discovers MTU, and queries routing tables to confirm the forwarding path.
This ensures test traffic is aligned with the live network characteristics, reducing false negatives from fragmentation, MPLS label stacking, or unexpected route asymmetry.
Phase 1
- RTT Validation to measure one-way delay and detect jitter before load testing.
- Path MTU Discovery to avoid fragmentation and preserve test accuracy.
- Route Verification against the expected QoS-enabled forwarding plane.
QoS Registry
A 16-class QoS registry is used to drive the generator, including standard DSCP mappings from Best-Effort to Network Control. Every class is exercised simultaneously for true service validation.
Concurrent Stream Generation
Concurrent subprocesses launch DSCP-marked load streams across all 16 QoS classes. This approach validates the full service profile in a single test run rather than only verifying isolated classes.
The engine detects congestion response, service policy enforcement, and queue behavior with the same traffic mix seen in production.
Dual Engine Backend
The framework switches between:
- iperf3 for bandwidth validation across TCP and UDP.
- hping3 for microsecond packet interval control and packet-sized QoS stress tests.
Essential Formulas
MSS
Max Segment Size
MTU
IPv4 + TCP headers = MTU - 40 bytes
Path Engineering
BDP
Pipe Fill Volume = (Average RTT × Link Rate) / 8
Window
Optimal TCP Window = BDP (Bytes)
Evidence Compilation
At the end of every run, the generator compiles a zero-dependency report with traffic metrics, DSCP behavior, packet loss statistics, and path characteristics.
This report is designed for network validation reviews, SLA evidence, and operational handoff to network architects.
Report Output
- End-to-end performance summary per QoS class
- Packet interval and microburst analysis
- Path MTU and RTT validation metadata
- Network control / queue policy compliance evidence
Integrated Video: QoS Traffic Generator Demonstration
QoS Documentation Summary
The accompanying QoS documentation covers service models, traffic markings, per-hop behaviors, congestion avoidance, and queuing architectures for enterprise and service provider validation.
Quality of Service Models
Quality of Service can be delivered using IntServ with per-flow reservations or DiffServ with node-by-node packet classification and forwarding behaviors. DiffServ is the dominant model for scalable service provider networks.
Traffic Markings
- Layer 2: Ethernet CoS uses 802.1p in 802.1Q, while MPLS uses CLP and TC fields.
- Layer 3: IP QoS markings include IP Precedence and the more granular DSCP values.
DSCP and Per-Hop Behaviors
DSCP values map to PHBs such as Class Selector, Assured Forwarding, and Expedited Forwarding. These markings determine queue placement, drop precedence, and priority treatment at every trusted hop.
Congestion Avoidance
RED and WRED are used to drop packets early before queues fill, preventing tail drop and avoiding TCP synchronization. Class-based WRED allows differentiated treatment by traffic class.
Queuing Architectures
- FIFO: Simple first-in first-out queuing with no prioritization.
- PQ / LLQ: Low-latency queuing for delay-sensitive traffic with strict priority scheduling.
- WFQ / CBWFQ: Weighted fair queuing with configured bandwidth allocations and class-based fairness.
Documentation
Download the full QoS technical guide used for this lesson. It includes DSCP tables, queuing comparisons, and Cisco policy-map examples.
Download QoS PDF