Configure support for voice

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Questions derived from the 642-812 – Building Converged Cisco Multilayer Switched Networks (BCMSN)
Cisco Self Test Software Practice Test.

 

Objective: Configure support for voice
SubObjective: Describe the characteristics of voice in the campus network

 

Item Number: 642-812.7.1.1
Multiple Answer, Multiple Choice

 

Which network problem areas are addressed with the implementation of QoS features? (Choose three.)

 

 

  1. Loss
  2. Delay
  3. Speed
  4. Jitter
  5. Bandwidth
  6. Redundancy

 

Answer:
A. Loss
B. Delay
D. Jitter

 

Tutorial:
Quality of service (QoS) is a set of tools and services that attempts to provide improved network services for voice, video, and data applications in terms of loss, delay, and jitter.

 

QoS provides the ability to predict and manage the network performance for specific types of traffic. At optimum times when bandwidth is plentiful, QoS is not an issue. In times of congestion, the QoS processes include classifying of traffic, setting traffic priorities, allocating dedicated bandwidth, and managing congestion.

 

An application’s network requirements are usually addressed in terms of loss, delay, and jitter. Data applications tend to be more sensitive to loss and less sensitive to minor delay or jitter. In comparison, interactive or “real-time” applications such as voice and video can tolerate intermittent loss of packets but delay and jitter can render the application unusable.

 

Delay is the amount of time it takes a packet to arrive at the final network destination after being transmitted into the network. There are a variety of factors that accumulatively contribute to the overall delay of a transmission including:

 

 

  • Packetization delay: This is the amount of time required to segment the original data stream into supported packets.
  • Serialization delay: This is the amount of time it takes to encode the bits of the packet onto the media (wire, fiber, etc.)
  • Propagation delay: This is the amount of time it takes to send a bit from one end of the media to the other.
  • Processing delay: This is the amount of time it takes to get the packet from the input queue to the output queue of a device.
  • Queuing delay: This is the amount of time that a packet sits in a queue.
  • Jitter is the variation in of the amount of delay one packet experiences versus the next.

 

Loss is the difference between how many packets made it through the network and how many were sent.

 

Reference:
http://www.cisco.com/warp/public/788/voip/delay-details.html#sourceofdelay

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