Changing the game of content delivery over IP
Der Artikel beschreibt am praktischen Beispiel, wie eine DMR-Netzwerkarchitektur inhärente Herausforderungen bei der Content-Zuführung über IP meistert.
Content providers are increasingly looking at the internet as a video distribution medium, but this alternative to satellite is only practical if the internet’s inherent limitations can be overcome.
The architecture of the internet fundamentally restricts its use for content delivery to multiple destinations. Built as a unicast system, the internet fundamentally lacks any native ability to send the same packet from one source to multiple destinations. Thus, to send a single video feed to multiple destinations over the internet, the source location must send multiple copies of the same content – one copy for each destination. When the number of destinations grows beyond just a few, this approach quickly becomes impractical. Additionally, because the internet is a ‘best efforts’ medium, lost packets need to be recovered once detected which for video means delays of multiple seconds must be added in order to allow for this recovery.
Through the application of unique “overlay” technology and the development of a managed network of data centers using LTN-developed and patented technology, LTN Global has overcome both fundamental challenges – i.e. latency and unicast – presented by the internet’s underlying architecture.
Bringing Exacting SLA Metrics to Internet Video Delivery LTN has built a global backbone of interconnected datacenters around its patented technologies, which include rapid error recovery (RER) and dynamic multi- carrier routing (DMR) algorithms. This architecture has established a fully managed video transport service over the internet with extraordinarily high reliability. The resulting network, exceeds 99.999 % availability with < 200 milliseconds latency so LTN can guarantee performance that matches and frequently exceeds those of
either satellite or fiber. The company can offer IP-based transmission which is not only a cost-effective alternative to those other delivery mechanisms, it is also much more flexible. LTN’s network, unlike satellite, allows for different content to be distributed to certain destinations if desired – think local advertising or localized content.
Dynamic Multi-Carrier Routing Network Architecture Within the LTN model, client appliances connect to LTN data centers and each data center has access to multiple Tier 1 carrier networks. As the upper web of elements in Figure 1 illustrates, traffic can flow between clients and data centers or between data centers over multiple carrier paths.
Using multiple carrier backbones (Tier 1 ISPs’ core IP networks), LTN’s DMR network architecture ensures high-availability end-to-end connectivity. Informed by real-time monitoring, backbone servers use near-instantaneous messaging and patented rapid routing algorithms to switch traffic between these different carrier planes (shown in green, blue, and red in Figure 1) – every few milliseconds if necessary – to take advantage of the best internet link and to ensure unimpeded arrival of the traffic flows. This therefore avoids the issues caused by the congestion, delay or sudden unavailability that regularly occur on the internet which unchecked cause “drop-outs” in the video flows.
Rapid Error Recovery (RER) Protocol
Routing and processing intelligence within its worldwide network of managed, interconnected data centers allows LTN to process data, monitor traffic, and perform other critical tasks that otherwise would be impossible. LTN’s patented error-correction protocol, RER, is used on every segment of the end-to-end delivery path for every flow, and it is this that allows errors to be detected (and either corrected or recovered) before being propagated further as they would over the underlying internet. The LTN RER protocol therefore enables rapid loss recovery within just 10–20 milliseconds. This is a radical improvement over typical end-to-end recovery times, which can take hundreds or even thousands of milliseconds. It is RER that enables LTN’s network to stay within such a small end-to-end latency budget — less than 200 milliseconds in almost all situations. LTN is in a position to transform the way content providers across the globe transport live video.
The Last-Mile Data Center
Intelligence across all of its data centers allows LTN to identify the data center closest to the target destination and to serve out copies of feeds only from that last-mile data center. By routing just one copy of a feed all the way to this last-mile data center, and only then processing and serving out multiple copies, LTN can reliably and efficiently deliver low-latency live and real-time video feeds to hundreds or even thousands of endpoints. Of course, LTN can support dual path routing to the destination from the last mile datacenter (or from the source to the last mile data center) to ensure continuity in the event of fiber cuts. In this way, the company brings multicasting capabilities to an architecture designed for unicast, thereby making the public internet a viable tool for bulletproof video distribution.
Enabling the Shift to IP-Based Video Delivery
Consistency, reliability, and low latency are all essential to live/real-time distribution of high-value content. Alone, the public internet or individual Tier 1 carrier backbones can’t meet these requirements on a 24/7 basis or even a second by second basis, nor can smart boxes/ technology deployed at the edge effectively address all of the issues without compromising timely delivery.
However, with an intelligent overlay network, such as that created by LTN, which can track, route, and re-route flows over multiple backbones within a matter of milliseconds, the internet can be leveraged successfully for continuous live video, despite the normal variable internet conditions. LTN’s DMR architecture combines with its RER protocols to deliver video reliably and with low latency. Content providers can rely on these proven technologies – LTN’s network has been in operation for more than 5 years and is already supporting delivery of high-value content for major media companies, to serve as a high-reliability alternative to satellite distribution.