QOS and Video

Discussion in 'Cisco' started by smoove, Aug 10, 2006.

  1. smoove

    smoove Guest

    I am getting ready to implement QOS for a video conferencing. It will be
    going across my WAN. The links are all 3mb. Does anyone have some sample
    configs or reccomendations for me to start with? I have never run any QOS.


    91 GSXR 750, 96 Chevy C1500, and 94 Suburban
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    smoove, Aug 10, 2006
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  2. Hi Smoove,

    You may wish to investigate this online Cisco Press Sample Chapter
    regarding Quality of Service Design Overview:

    QoS Requirements of Video


    Two main types of video traffic exist: Interactive-Video
    (videoconferencing) and Streaming-Video (both unicast and multicast).

    Each type of video is examined separately.


    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

    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

    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.


    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.

    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

    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.


    This QoS Requirements of Video sample chapter is from the Cisco Press

    End-to-End QoS Network Design: Quality of Service in LANs, WANs, and



    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
    1293 Hendersonville Road, Suite 17
    Asheville, North Carolina USA 28803
    USA & Canada: 877-549-2680
    International: 828-277-7272
    Fax: 775-254-3558
    AIM: R2MGrant
    BradReese.Com - Cisco Authorized Distributors Worldwide
    www.BradReese.Com, Aug 10, 2006
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  3. Rob

    Rob Guest

    Brad's reply is your best bet. Unfortunately, you asked the timeless
    question about where to start with QoS and that subject is huge. It's
    the equivalent of "How do I build a house?" instead of something like
    "How do I lay down carpet?" The whole is quite large compared to the

    On Wed, 9 Aug 2006 16:38:17 -0700, "smoove" <>

    >I am getting ready to implement QOS for a video conferencing. It will be
    >going across my WAN. The links are all 3mb. Does anyone have some sample
    >configs or reccomendations for me to start with? I have never run any QOS.
    Rob, Aug 11, 2006
  4. www.BradReese.Com, Aug 11, 2006
  5. sando


    Mar 24, 2009
    QoS of video (streaming) measurement

    Dear Mr Reese,

    I have been downloading and installing any network or video quality programs just to measure the QoS items such as audio bit rate, video bit rate, jitter, buffer (loss), packet (loss), or any statistics shown by windows media player (classic).

    Yet, I haven't found any program that can record the log of such QoS statistics.

    Is there any way you can carry out my problems?
    Because I am frustrated almost.
    Thank you before.


    Attached Files:

    sando, Mar 24, 2009
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