QoS - The Need For QoS

5 important questions on QoS - The Need For QoS

Network latency or End to End delay is the time it takes for packets to travel from the source to the destination. Which 4 types of Delay can Network Latency be broken down into?

1. Propagation Delay (Fixed)
2. Serialization Delay (Fixed)
3. Processing Delay (Fixed)
4. Delay variation (variable)

What is the Propagation Delay?

The time it takes the packet to travel the media like Fiber Optic or Copper by the speed of light.

What is the Serialization Delay?

The time it takes to place all the bits of a packet onto a link. Can be calculated by dividing the packets size in bits by the link speed in bits. 1500 byte packet on 1Gbps link is 12.000 / 1000.000.000 = 0.12ms.
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What is the processing delay?

The time it takes a networking device to take the packet from the input interface and place it onto the queue of the outgoing interface.
Depends on the following factors:
CPU Speed
CPU Utilization
IP Packet Switching mode (Process switching, Hardware or software CEF)
Router Architecture (Centralized or Distributed)
Configured features on input and output interfaces.

What is Delay Variation?

Delay Variation is also reffered to as Jitter. It is the difference in latency between packets in a single flow.
It is experienced due to Queueing delay during periods of network congestion.

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