Hi Smoove,
You may wish to investigate this online Cisco Press Sample Chapter
regarding Quality of Service Design Overview:
QoS Requirements of Video
http://www.ciscopress.com/articles/a...2-9ab5cc199d74
Two main types of video traffic exist: Interactive-Video
(videoconferencing) and Streaming-Video (both unicast and multicast).
Each type of video is examined separately.
Interactive-Video
When provisioning for Interactive-Video (video conferencing) traffic,
the following guidelines are recommended:
Interactive-Video traffic should be marked to DSCP AF41; excess
videoconferencing traffic can be marked down by a policer to AF42 or
AF43.
Loss should be no more than 1 percent.
One-way latency should be no more than 150 ms.
Jitter should be no more than 30 ms.
Assign Interactive-Video to either a preferential queue or a second
priority queue (when supported); when using Cisco IOS LLQ,
overprovision the minimum-priority bandwidth guarantee to the size of
the videoconferencing session plus 20 percent. (For example, a 384-kbps
videoconferencing session requires 460 kbps of guaranteed priority
bandwidth.)
Because IP videoconferencing (IP/VC) includes a G.711 audio codec for
voice, it has the same loss, delay, and delay-variation requirements as
voice-but the traffic patterns of videoconferencing are radically
different from those of voice.
For example, videoconferencing traffic has varying packet sizes and
extremely variable packet rates. These are illustrated in Figures 2-2
and 2-3.
Figure 2-2 Videoconferencing Traffic Packet-Size Breakdown
Figure 2-3 Videoconferencing Traffic Rates (384-kbps Session Example)
The videoconferencing rate is the sampling rate of the video stream,
not the actual bandwidth that the video call requires. In other words,
the data payload of videoconferencing packets is filled with 384 kbps
of voice plus video samples. IP, UDP, and RTP headers (40 bytes per
packet, uncompressed) need to be included in IP/VC bandwidth
provisioning, as does the Layer 2 overhead of the media in use. Because
(unlike VoIP) IP/VC packet sizes and rates vary, the header overhead
percentage also varies, so an absolute value of overhead cannot be
calculated accurately for all streams. However, testing has shown that
a conservative rule of thumb for IP/VC bandwidth provisioning is to
assign an LLQ bandwidth equivalent to the IP/VC rate plus 20 percent.
For example, a 384-kbps IP/VC stream adequately is provisioned with an
LLQ of 460 kbps.
NOTE
The Cisco LLQ algorithm has been implemented to include a default burst
parameter equivalent to 200 ms of traffic. Testing has shown that this
burst parameter does not require additional tuning for a single IP
videoconferencing (IP/VC) stream. For multiple streams, this burst
parameter can be increased as required.
Streaming-Video
When addressing the QoS needs of Streaming-Video traffic, the following
guidelines are recommended:
Streaming-Video (whether unicast or multicast) should be marked to DSCP
CS4, as designated by the QoS Baseline.
Loss should be no more than 5 percent.
Latency should be no more than 4 to 5 seconds (depending on the video
application's buffering capabilities).
There are no significant jitter requirements.
Guaranteed bandwidth (CBWFQ) requirements depend on the encoding format
and rate of the video stream.
Streaming-Video is typically unidirectional; therefore, remote branch
routers might not require provisioning for Streaming-Video traffic on
their WAN or VPN edges (in the direction of branch to campus).
Nonorganizational Streaming-Video applications (either unicast or
multicast), such as entertainment video content, may be marked as
Scavenger-DSCP CS1, provisioned in the Scavenger traffic class and
assigned a minimal bandwidth (CBWFQ) percentage. For more information,
see the "Scavenger Class" section, later in this chapter.
Streaming-Video applications have more lenient QoS requirements because
they are not delay sensitive (the video can take several seconds to cue
up) and are largely not jitter sensitive (because of application
buffering). However, Streaming-Video might contain valuable content,
such as e-learning applications or multicast company meetings, in which
case it requires service guarantees.
The QoS Baseline recommendation for Streaming-Video marking is DSCP
CS4.
An interesting consideration with respect to Streaming-Video comes into
play when designing WAN and VPN edge policies on branch routers:
Because Streaming-Video is generally unidirectional, a separate class
likely is not needed for this traffic class in the branch-to-campus
direction of traffic flow.
Nonorganizational video content (or video that's strictly entertainment
oriented in nature, such as movies, music videos, humorous commercials,
and so on) might be considered for Scavenger service, meaning that
these streams will play if bandwidth exists, but they will be the first
to go during periods of congestion.
http://www.ciscopress.com/articles/a...2-9ab5cc199d74
This QoS Requirements of Video sample chapter is from the Cisco Press
Book:
End-to-End QoS Network Design: Quality of Service in LANs, WANs, and
VPNs
http://www.ciscopress.com/bookstore/...2-9ab5cc199d74
Authors:
Tim Szigeti, CCIE No. 9794, is a member of the Enterprise Solutions
Engineering Design Team at Cisco Systems.
Christina Hattingh is a member of the technical staff in the
Multiservice Customer Edge Business Unit of Cisco Systems.
Hope this helps.
Brad Reese
BradReese.Com - Cisco Technical Forums
http://www.bradreese.com/cisco-technical-newsgroups.htm
1293 Hendersonville Road, Suite 17
Asheville, North Carolina USA 28803
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