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Optimising video across the WAN

Making effective use of your network.

Real-time applications, like video surveillance, video streaming and video conferencing currently account for over 30% of world-wide typical enterprise’s application mix (Source: Gartner 2009), and are expected to grow faster than any other type of traffic. These applications behave quite differently than traditional enterprise applications like file, e-mail and Web services – especially across a wide area network (WAN).

WAN optimisation appliances have several unique architectural advantages that make it ideal for the optimisation of real-time traffic. These include:

* Protocol agnostic approach to WAN optimisation.

* Real-time loss mitigation. Network Integrity features correct for dropped and out of order packets in real-time. This avoids packet re-transmissions, which can severely degrade the quality of real-time applications across the WAN.

* Low insertion latency. WAN optimisation appliances perform all optimisations in real-time, introducing little or no additional latency when handling multimedia traffic.

Video streaming/video on demand

Video streaming involves the transfer of content over the WAN for viewing in real-time. When the content is requested by end users (i.e. subscribers), it is often referred to as video on demand (VoD).

When video content is delivered across a WAN in real-time, there are several technical challenges that must be addressed. For one, even though the streams are often pre-compressed, they still can consume quite a bit of bandwidth. This is especially true when many users are viewing the same content. Secondly, video streaming and real-time VoD is very susceptible to latency and loss on the WAN.

Long distances and/or frequent packet re-transmissions will adversely impact video quality, and subsequently ruin an end user’s experience. WAN optimisation overcomes the above challenges in the following ways:

* WAN Deduplication: WAN optimisation appliances eliminate the transfer of repetitive data across the WAN using real-time disk based deduplication. This works within a stream as well as between video streams. Therefore, if many users are attempting to view the same content from a single location, that content only needs to be delivered once across the WAN. This improves download times and saves on WAN bandwidth expenditures.

WAN optimisation appliances also perform header and payload compression to improve the performance of non-repetitive video traffic. Deduplication and compression techniques are performed on all IP traffic, including video applications that run over UDP.

* Network Integrity: WAN optimisation appliances uses real-time Forward Error Correction (FEC) to correct for dropped packets, and Packet Order Correction (POC) to correct for out of order packets. These avoid packet re-transmissions, which can hurt the performance of real-time video across the WAN. Network Integrity features work on all IP traffic, including video streaming and VoD applications that run over UDP.

* Quality of Service: WAN optimisation appliances robust quality of service (QoS) policies can be used to prioritise video streams and to guarantee these services receive adequate network resources (i.e. bandwidth) across the WAN.

While performance varies depending on traffic patterns and content, the following results are often experienced when WAN optimisation is deployed in conjunction with video streaming and real-time VoD:

* Improved quality of video stream across the WAN (i.e. reduced pixelation).

* Up to 99% deduplication, especially when multiple streams are sent to the same location across the WAN.

* Benefits are most noticeable on ‘lossy’ WANs, such as MPLS or Internet VPNs, and when network congestion is present.

Below are some key questions to ask to determine if WAN optimisation is right for your video streaming environment:

* Have users experienced poor video quality, such as dropped or choppy video streams?

* Are you concerned that the increasing demand video is placing on your network will cause problems with this and other applications going across your WAN?

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