The Bequant Bandwidth Management functionality, which is integrated in the Bequant BQN product, allows you to limit the speed of certain services, identified by DPI or by IP addresses, enforcing a maximum speed for those services per user. For example, a 2 Mbps limit for video streaming services downloads, per user.
For UDP services or other non-TCP services, speed is enforced like in other QoS products, with a speed-limiting queue which will drop packets when it overflows. However, for TCP-based services (the majority), the speed limitation is enforced using TCP mechanisms, which, using the window parameter in TCP acknowledgements, avoids dropping any packets. The originating server is slowed down directly. Moreover, the TCP optimization will still improve the speed and quality of the service, up to the configured limit. Finally, all the limited flows (TCP, UDP or other) are granted a fair share of the available limited badwidth, which also enhances the quality of the now limited service.
The following graph shows the results of limiting streaming video speed to 4 Mbps per user in a Wireless ISP network. The 4 Mbps limitation was enforced during even hours of the day, while no limitation was set on odd hours of the day, and the total volume of traffic sent every hour, for the whole network, was measured for four days. It can be seen that the overall volume of traffic was significantly lower (around 10% lower), and that the peaks in traffic were also lower when limiting to 4 Mbps. All these results were obtained with no customer complaints due to quality
Limiting the maximum speed of streaming video services with Adaptive Bit Rate clients (most video streaming services use ABR) can help reduce congestion at peak hours and the overall traffic. ABR streaming clients adapt the resolution, and therefore the volume of traffic they use, to the measured download speed. If the speed is reduced to a reasonable number, the resolution willl be somewhat reduced without noticeable effects to the customer, and the volume of traffic used could be significantly reduced (since ABR video streaming is the main volume consumer in most networks). In cellular mobile networks, where a more restrictive limitation is possible (because video resolution can be lower in handheld devices), we have measured reductions in overal volume of around 18%.
In the previous experiment, we also measured the average latency from our equipment up to the network subscribers, and found it to be significantly lower, by around 5 milliseconds, during the even hours, when video streaming traffic had a speed limitation, as can be seen in the following graph. This is due to the fact that video stremaing tends to take all the available bandwidth, and that can fill up buffers in the network, which increases latency. By limiting video streaming total speed per user to a value below the subscribers' plan limit, we ensure those limits are not reached and some bandwidth is left for applications like online gaming or voice-over-IP, which will benefit from the latency reduction.
The applications to limit can be identified by DPI or IP address, or a combination of both. As part of the Support & Maintenance service, Bequant provides signatures for popular services. The speed limitation can be applied to only certain client IP addresses, or only when the overall traffic and the network exceeds a threshold (since it may not be necessary to enforce any bandwidth limitation when the total traffic in the network is low). It is also possible to set different speed limitation to different applications or to different users.