Quality of Service (QoS)

QoS is the set of techniques to guarantee a required level of network performance for different types of traffic.

QoS parameters

• Bandwidth (throughput)
• Delay (latency)
• Jitter (variation in delay)
• Reliability / packet loss

Techniques to achieve QoS

• Scheduling: FIFO, priority queuing, weighted fair queuing
• Traffic shaping: leaky bucket, token bucket
• Admission control: accept a flow only if resources are available
• Resource reservation: RSVP

Models

• Integrated Services (IntServ): per-flow reservation
• Differentiated Services (DiffServ): per-class marking (DSCP) and treatment

Applications

VoIP, video conferencing, streaming and online gaming, which are delay- and jitter-sensitive, unlike email or file transfer.