Computer Networking Fundamentals

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.