Media Flow Controller Overview : Media Flow Controller Functions : AssuredFlow™

The AssuredFlow feature assures that Media Flow Controller provides the required bandwidth for a connection so that media encoded at different bit-rates are delivered at approximately the encoded bit-rate rather than the fastest possible. This helps optimize use of the available bandwidth per session along with contributing to the viewing experience of the end user.
It also may be tied to the end-user’s service level agreement (SLA). This ensures that bandwidth is not wasted by sending data at a rate higher than the rate at which it is being consumed (decoded) by the client. Furthermore, it ensures sufficient bandwidth is available (reserved) for clients that need higher bit rate video. Examples include:
Assured-flow rate (AFR) is the parameter through which Media Flow Controller provides customer control of the AssuredFlow feature. AFR is specified in Kbps, and its intent is to ensure that Media Flow Controller reserves at least the set rate in bandwidth for each delivery session. Clearly, the sum of AFR can't exceed the aggregate bandwidth of the server. To be more specific, if an interface, say, GbE, has “n” sessions, AssuredFlow can guarantee that the sum of AFR assigned to each session does not exceed the capacity of the GbE port, or 1Gbps. Juniper Networks recommends that the sum of AFR be set to 80% to 90% of the link speed, for best performance. Further, the configured AFR should reflect the average bandwidth the target origin server is set to deliver media. For example, if a portal delivers video to users at an average rate of 750 Kbps, AFR should be set to reflect this value (e.g. 750 Kbps). Assured-flow rate can be set globally or through a virtual player configuration. Traffic is served at the configured AFR, or the dynamic AFR set by the virtual player, up to the set maximum session bandwidth.
It is not uncommon to have portals set the logic in their player to signal the AFR on each session. In that case, the signaled AFR overrides the configured AFR. AFR is disabled by default, which means Media Flow Controller does not assure a delivery rate. When AFR is disabled in Media Flow Controller, player-signaled AFR is still effective.
Admission Control
Session admission control provides a mechanism to avoid bandwidth overload; this is an important part of AssuredFlow. Before a new session is admitted, a series of checks across various resources determines whether the session can be admitted. A new session is defined as the first GET request received within a new network connection. Existing sessions are not subject to this control. The following are the various checks that can reject a new session.
The AFR for the request is based on the URL and/or other query parameters and Media Flow Controller can determine that this AFR cannot be serviced given the existing bandwidth being served on that port.
Logging and statistics for which Media Flow Controller module refused session admission are provided in the errorlog.

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Media Flow Controller Administrator's Guide and CLI Command Reference
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