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Cisco AVVID Network Infrastructure Enterprise Quality of Service Design
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Chapter 1 Overview
Why is Quality of Service Required for AVVID?
Tip
Detailed calculations of call control traffic can be found in the "Network Infrastructure Requirements"
chapter of the IP Telephony Solution Reference Network Design Guide.
Quality of Service Requirements for Video
When addressing the QoS needs of streaming video traffic, keep the following in mind:
·
Loss should be no more than 2%.
·
Latency should be no more than 4-5 seconds (depending on video application's buffering
capabilities).
·
There are no significant jitter requirements.
·
Bandwidth requirements depends on the encoding and rate of video stream.
·
Non-entertainment streaming video should be provisioned into the "Silver" data-traffic class. (The
silver data class is discussed in
"Provisioning for Important Data Traffic" section on page 1-9
.)
For video content distribution, keep the following in mind:
·
Streaming video content is delay and delay variation insensitive.
·
Streaming video requires large file transfers (traffic patterns similar to FTP sessions).
·
Try to restrict to distribution to less-busy times of day.
·
Provision as "less-than-best-effort" data. (The less-than-best-effort data class is discussed in
"Provisioning for Important Data Traffic" section on page 1-9
.)
When addressing the QoS needs of video conferencing traffic, keep the following in mind:
·
Loss should be no more than 1%.
·
One-way latency should be no more than 150-200 ms.
·
Average jitter should be no more than 30 ms.
·
The minimum bandwidth guarantee is the size of the video conferencing session + 20% (meaning
that a 384 kbps video conferencing session requires 460 kbps guaranteed priority bandwidth).
There are two main types of video applications: streaming video (such as IP/TV, which may be either
on-demand or multicast) and interactive video (such as video conferencing).
Streaming Video
Streaming video applications have more lenient QoS requirements, as they are delay insensitive (the
video can take several seconds to 'cue-up'), and are largely delay variation insensitive (due to application
buffering). Streaming video may contain valuable content, as in the case of an E-learning application,
and therefore may require service guarantees via QoS. Streaming video would be appropriately
provisioned in the "Silver" class of data traffic.
When you are provisioning for streaming video, you should also take into account the video content
distribution requirements. Video file distribution is very similar to FTP traffic in nature and can have a
major impact on network performance (due to the file size). Distribution traffic should be managed to
avoid impacting the network. For example, video content transfers could be limited to off-peak hours or
treated as "less-than-best-effort" traffic.