Policy Control And Mobile Video
There is no question video is both popular ( e.g., YouTube is now the second-largest search engine) and consumes tremendous amounts of network resources relative to almost any other application.
In 2009, Cisco’s Visual Networking Index projected that mobile video will grow 66-fold from 2009 to 2014, to the point where it will consume 66 percent of all mobile bandwidth by 2014. Clearly, finding ways to mitigate the network impact of mobile video in a way that still meets consumers’ interests would be beneficial to wireless carriers.
Policy control is a relatively new network technology (known by the 3rd Generation Partnership Project [3GPP] as a “Policy and Charging Rules Function” or PCRF) that allows operators to dynamically control bandwidth, charging, consumption and other network factors for a subscriber’s entire data session or for one or more particular applications. The controls are applied based on business rules defined by the network operator, taking into account subscriber, network and application conditions as well as such other factors as time of day, day of week and so on.
In order to do control services, the PCRF gets policy requests from a system or application; processes the policy rules for that particular type of request according to the conditions at the time; and then instructs one or more other network systems to change the behavior of the service, if needed. In this way, the network performance, charge, allowed consumption, etc., for each individual user can be personalized according to his or her chosen services.
The initial uses for a PCRF typically have been for bandwidth control and user notification of heavy-use subscribers, although a growing number of mobile operators now are using the PCRF to manage specific applications like video, voice over IP and peer to peer.
The main advantage of a standard PCRF-based approach compared to earlier static provisioning of services is the ability to manage selectively a wide range of network treatments to deliver the best service possible to the maximum number of subscribers, given a certain set of network constraints. There is a tight relationship between the terms of service for each tariff and the rules applied in the PCRF – e.g., “based on the service you have selected and the conditions at this time, this is how the service will work.”
There are a number of potential treatments when it comes to policy control of mobile video:
Control (blocking or optimizing) of video when users go over a certain overall usage threshold: The idea is to save the user from large bills when overage fees are being charged but otherwise allowing video. The PCRF can push the appropriate policies into the network elements to block or control video based on usage information.
User self-selection into a service that does not allow video, allows only optimized video, only allows video in off-peak hours or only allows video to particular applications (e.g., work-related apps but no YouTube or browser-based video) with the potential to override the video treatment if user accepts charges: Think of this as a generalized video form of the 0.facebook.com service some mobile operators have adopted. Such high levels of customizations can be managed by the PCRF and pushed by the PCRF to the appropriate gateways in the network to provide the dynamic experience.
Use of a separate, video-specific quota bucket in addition to the standard overall usage quota, and being able to “subtract” any video specific usage from the overall data bucket, if necessary.
Application of service-specific “optimization” techniques for certain classes of users or devices at certain times of day or locations in the network.
Creation of “managed IPTV services” where, if the user subscribes to the service, usage is not counted towards the user’s overall data bucket: This could be delivered in a similar manner to how fixed broadband operators deliver IPTV services using the same IP network that delivers Internet access.
When a network becomes congested and mobile video is consuming too much of the network’s resources (thus affecting the quality of service for many other users applications), the operator may choose to throttle video traffic on those congested nodes: Such capabilities would help preserve network integrity and service, and keep video from potentially overwhelming the network.
PCRF And The Network
In order to technically realize these services, there are a number of network functions that work in conjunction with the PCRF to support the use cases. The PCRF acts as the central coordinator of policy actions to be applied in the network, thereby acting as the “brain” for the main gateways in the network.
This act of coordination is critical so that the treatment of data sessions and applications are not taken in isolation. When decisions are made locally in individual "boxes" in isolation of the bigger picture of what is happening in the network, the subscriber experience can be impacted severely, and the network performance will be impaired. Here are some examples:
Ability to detect and block video: One of the main functions of DPI is to detect, report and apply certain QoS controls to particular applications. Most DPI vendors have solid functionality around video in this regard.
Ability to detect and “optimize” video: A number of mobile Internet gateways (MIGs) claim to have the ability to “optimize” video by limiting video players from pre-loading more video than is currently being played, adding additional compression or allowing only SD-size content.
General data usage counter/quota: Most GGSNs, DPIs and MIGs now have the ability to count usage for the user’s entire data session for the session duration. Such hardware as the Tekelec Policy Server can control this mechanism using standard interfaces to control usage over multiple sessions in a similar manner to a prepaid billing system without the need to modify the existing biller.
Video-specific usage counter/quota: A smaller set of DPIs and MIGs have the ability to count usage for particular applications like video in addition to their detection, reporting and control functionality. This usage counter could be subtracted from the overall usage counter as in the case of a managed video service or counted separately in the case of a video-specific quota.
Subscriber database for the network: Given the need to manage data services according to each subscriber’s particular profile and usage, the deployment of a supplementary subscriber database for network purposes is becoming common. This database is referred to as a Subscriber Profile Repository (SPR) by 3GPP.
User notification and self-selection: Alongside the subscriber database, the ability to notify and/or let users modify their services is becoming more common. The simplest form of notification could be having the PCRF send the user a SMS upon some action ( e.g., “you have gone over your video quota and, therefore, video more than 256 Kbps will be blocked”). Interactive portals that would allow the user to choose to accept or modify the service change could be implemented as well.
Gateway for over-the-top (OTT) providers to request special charging treatment for video: In order to allow OTT providers to trigger special treatment of video services, these same mechanisms must be exposed in a secure but easy-to-use API. In the long run, there are some industry efforts from the GSMA and the Wholesale Application Community (WAC) to standardize a function like this so that OTT providers would have a single API throughout the world.
Here are a few additional notes of importance:
Separation of video traffic: Note that video can be treated separately from standard data traffic by the use of a separate IP traffic filter and a potentially separate radio bearer. This will allow such low-bandwidth services as email and simple Web browsing to continue unaffected.
Traffic steering: One dilemma of DPI and MIGs is how to use their technology selectively so that only the portion of traffic that might need to be controlled is sent through the box rather than all network traffic. To send all network traffic through the extra processing would be expensive and would increase the risk of an outage. One of the key functions of a PCRF is to steer traffic selectively to the DPI (for example, for only those users that have opted into a video-optimized service).
Network neutrality: The topic of management of mobile video over IP is politically sensitive and, as such, has a strong role in the net-neutrality debate. While there are a number of potential outcomes in each country, one common thread throughout most debates is the importance of a customer being able to choose how the service will behave. Most regulatory regimes seem to be giving room for controls if the user is able to make tradeoffs, whether in the form of options upon service startup or a portal to self-select and modify services on demand.
Randy Fuller is director/Strategic Marketing for Tekelec. Contact him at [email protected]