8 Questions
What is the term used to describe a variation in delay?
jitter
What is the role of network devices in the IntServ QoS model?
To ensure resources are available before traffic is sent
What type of traffic is commonly provided the most preferential treatment in QoS models?
voice traffic
What happens when the memory queue of a device fills up and new network traffic is received?
The network device will drop the arriving packets
What is the primary characteristic of voice traffic?
It is delay sensitive
What QoS model provides the highest guarantee of QoS but is very resource intensive?
IntServ
What mechanism compensates for jitter in an audio stream?
playout delay buffer
In QoS models, which type of traffic is commonly placed in the strict priority queue (PQ) when LLQ is being used?
voice traffic
Study Notes
Network Quality of Service (QoS)
- Jitter is the term used to indicate a variation of delay.
- Latency is the time it takes for a packet to travel from a source to a destination device and return.
IntServ QoS Model
- Network devices play a crucial role in ensuring that resources are available before traffic is allowed to be sent by a host through the network.
- IntServ QoS model is very resource-intensive and provides the highest guarantee of QoS.
- When an edge router using IntServ QoS determines that the data pathway cannot support the level of QoS requested, data is not forwarded along the pathway.
Network Devices and Traffic
- IP phones are classified as trusted endpoints.
- Network devices drop arriving packets when their memory queue fills up and new network traffic is received.
- Voice traffic is delay-sensitive and consumes few network resources.
Traffic Classification and Queuing
- Best-effort is the only QoS model with no mechanism to classify packets.
- Cisco recommends placing voice traffic in the strict priority queue (PQ) when low latency queuing (LLQ) is being used.
- CBWFQ is a queuing mechanism that supports user-defined traffic classes.
- Voice traffic is commonly provided the most preferential treatment over all other application traffic.
Traffic Congestion and Jitter
- Congestion occurs on a converged network with voice, video, and data traffic when the request for bandwidth exceeds the available bandwidth.
- Jitter is compensated for in an audio stream by using a playout delay buffer, which buffers packets and then replays them outbound in a steady stream.
Test your knowledge of computer networking concepts, including delay variations, network performance, and quality of service models.
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