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350-801 · Question #397

What is a reason for using a Diffserv value of AF41 for video traffic?

The correct answer is D. Video traffic can tolerate a packet loss of up to 1% and latency of 150 milliseconds. AF41 is a DiffServ value commonly assigned to video traffic because video requires low packet loss, ideally below 1%, and low latency, typically around 150 milliseconds, for an acceptable user experience.

Media and QoS

Question

What is a reason for using a Diffserv value of AF41 for video traffic?

Options

  • AVideo traffic cannot tolerate any packet loss and has a latency of 150 miliseconds
  • BVideo traffic can tolerate up to 10% packet loss and latency of 10 seconds
  • CVideo traffic can tolerate up to 5% packet loss and latency of 5 seconds
  • DVideo traffic can tolerate a packet loss of up to 1% and latency of 150 milliseconds

How the community answered

(39 responses)
  • A
    5% (2)
  • C
    3% (1)
  • D
    92% (36)

Why each option

AF41 is a DiffServ value commonly assigned to video traffic because video requires low packet loss, ideally below 1%, and low latency, typically around 150 milliseconds, for an acceptable user experience.

AVideo traffic cannot tolerate any packet loss and has a latency of 150 miliseconds

While video is highly latency-sensitive (150ms is a common threshold), it can tolerate a small amount of packet loss (e.g., up to 1%), so stating it 'cannot tolerate any packet loss' is incorrect.

BVideo traffic can tolerate up to 10% packet loss and latency of 10 seconds

Tolerating 10% packet loss and 10 seconds of latency would lead to an extremely poor and unusable video experience, making this an incorrect QoS requirement for real-time video.

CVideo traffic can tolerate up to 5% packet loss and latency of 5 seconds

Tolerating 5% packet loss and 5 seconds of latency is still far too high for real-time video, which would result in severe quality degradation and interruptions.

DVideo traffic can tolerate a packet loss of up to 1% and latency of 150 millisecondsCorrect

AF41 (Assured Forwarding Class 4, Drop Preference 1) is selected for video traffic because video applications are highly sensitive to network impairments, necessitating very low packet loss (typically less than 1%) and minimal latency (around 150 milliseconds one-way) to maintain call quality.

Concept tested: DiffServ AF41 for video QoS

Source: https://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/Campus/campqos/qos_book_main/qos_ch3.html

Topics

#Diffserv#QoS for Video#AF41#Packet Loss & Latency

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