Cisco Cisco ASR 5500
Mobile Video Gateway Overview
Features and Functionality ▀
MVG Administration Guide, StarOS Release 17 ▄
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Figure 12. Video Pacing During Bad Channel Conditions
In the figure above showing bad channel conditions, when channel conditions worsen, the actual downloaded video
bytes cannot keep up with the ideal pacing rate. Nonetheless, if the channel recovers in time, the download rate is still
above the blue line representing the minimum data required for smooth playback, and video pacing continues to
maintain b bytes of data above this lower limit.
bytes cannot keep up with the ideal pacing rate. Nonetheless, if the channel recovers in time, the download rate is still
above the blue line representing the minimum data required for smooth playback, and video pacing continues to
maintain b bytes of data above this lower limit.
Video Pacing Functions
The video pacing feature includes four main functional components, as follows:
Pacing Start Trigger: The pacing start trigger is part of the Active Charging Service for video pacing. When a
rule definition in the Active Charging Service identifies a packet flow as a video flow, and the corresponding
charging action for video pacing is enabled, the pacing start trigger invokes video pacing enforcement for the
video flow. It sets the video bit rate and initial burst size from the subscriber policy, which is configured for
subscribers in the source context as part of the active charging rulebase. It then becomes dormant.
charging action for video pacing is enabled, the pacing start trigger invokes video pacing enforcement for the
video flow. It sets the video bit rate and initial burst size from the subscriber policy, which is configured for
subscribers in the source context as part of the active charging rulebase. It then becomes dormant.
Some mobile devices such as the Apple iPhone can serve video clips using multiple TCP sessions, such as
when an iPhone user skips forward in the middle of playback and the iPhone closes the existing TCP session
and starts a new one. When multiple TCP sessions are used to download the same video, the pacing start
trigger gets invoked once per video flow, and the video pacing feature correlates these flows to the same video
object to continue pacing enforcement from where the last TCP flow left off. When multiple TCP flows are
used to download different videos, video pacing is performed independently per flow.
when an iPhone user skips forward in the middle of playback and the iPhone closes the existing TCP session
and starts a new one. When multiple TCP sessions are used to download the same video, the pacing start
trigger gets invoked once per video flow, and the video pacing feature correlates these flows to the same video
object to continue pacing enforcement from where the last TCP flow left off. When multiple TCP flows are
used to download different videos, video pacing is performed independently per flow.
Video Pacing Enforcement: After the initial burst of video content, the video pacing enforcement function sets
the optimal video download rate for the incoming downlink packets using a token bucket algorithm. Video
pacing occurs based on the settings configured via CLI command options.
pacing occurs based on the settings configured via CLI command options.
Video Rate Determination: The video rate determination function is a software algorithm that examines the
initial HTTP RESPONSE packets and video metadata packets to determine the encoded bit rate of the video. It