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The arrival of new Content Delivery Networks (CDNs) this year is set to improve quality and reduce bandwidth costs for broadcasters and over-the-top (OTT) service providers delivering programming over the Internet. One of the largest developments is BT Wholesale’s Content Connect CDN, which is about to start offering capacity to BT Retail and other service providers, increasing the options available for reducing congestion on core and backbone IP networks.
The idea of the CDN is quite old, having first been deployed by Cisco and others within the Internet over a decade ago to distribute and then cache popular websites on servers near the edge of the network, closer to the users consuming it. This approach reduces congestion within the core and backhaul networks. The difference now is that CDNs are being dedicated to video, with increasingly sophisticated techniques for guaranteeing QoS and deciding in real-time which video to offload over the CDN and where to distribute it.
BT’s Content Connect will play an important role in the YouView initiative, the successor to the BBC’s Project Canvas, to develop a platform for accessing aggregated on-demand and catch-up programming content from TVs via the Internet. Launch of YouView has been delayed until 2012, but not because of problems with Content Connect, which the BBC and other broadcasters expect will be capable of providing TV-quality QoS.
However, the CDN alone cannot guarantee QoS over the Internet unless it reaches as far as the DSLAM, if the access is over DSL. Otherwise there may still be congestion over the link between the DSLAM and CDN edge server. CDNs therefore tend to operate in conjunction with some adaptive streaming technique to reduce the impact of congestion on video by splitting the stream up into smaller packets. CDNs do, however, contribute significantly to QoE by reducing the distance video has to be streamed to the end user, bringing latency down. That is particularly important for interactive video applications.
Apart from quality, CDNs will increasingly reduce costs for content owners and operators by replacing current dedicated connections, which are more expensive, according to Nimrod Ben-Natan, VP of Products, Solutions and Strategy at leading video technology company Harmonic. “We are seeing opportunities to use CDNs as an alternative to leased and expensive IP networks or satellite transponders, based on adaptive streaming formats, which makes the video delivery more resilient against network bandwidth changes,” he says.
The other side of the coin is that operators can use the CDN approach in their own networks to become wholesale content distributors themselves. This does not only apply to telcos. The opportunity has come to the attention of larger cable operators, where CDNs are rising rapidly up the agenda, partly because of their potential for attracting new revenue in wholesale content distribution, according to Murali Nemani, Director of Service Provider Video Marketing at Cisco, supplier of the platform for BT’s Content Connect.
Nemani identifies a clear trend among cable operators towards CDN deployment within their networks. This is not just to attract new revenue, but also to streamline their own content distribution. In a sense this is part of a move towards CDN 2.0, involving more intelligent distribution in real-time, taking account of ongoing changes in consumption by consumers.
CDN 1.0 was about distributing content out to edge servers in advance, anticipating demand. This would happen for a major football match, avoiding huge numbers of multicast streams swamping the core network. But under CDN 2.0, the network better accommodates the fact that even live content is not consumed absolutely simultaneously by everybody – some viewers might want to delay streaming a minute or so while they make a cup of tea.
The modern CDN allows the network to detect when a particular channel is becoming popular enough to merit caching locally, and also determines how much to cache. It may be that the cache only has to store a minute or two of the stream at any time, allowing for those viewers who have delayed watching a short time to make that drink, perhaps. It may then be more cost-effective to deliver on a unicast basis to those people who watch it after a longer delay over five minutes, for example. CDNs are becoming increasingly clever at making such distinctions on economic or capacity grounds.
The other noteworthy development is that CDN technology is becoming embedded into the network, along with other components including transcoders. “We are also seeing interest in products and solutions that simplify the whole video delivery chain by collapsing functions such as decoding, logo insertion, audio levelling, closed captioning and others into integrated devices such as encoders and playout servers,” Harmonic’s Ben-Natan observes. That is another story, but is part of the overall trend towards distribution networks becoming better optimised for video, with CDNs playing an important part.