Video Routing: A look at what's next
Feb 1, 2009 12:00 PM, By Neil Maycock
The variable network latency and lack of guaranteed data delivery seem to suggest that Ethernet cannot deliver the quality of service required for video distribution. However, solutions are provided by protocols higher up in the ISO Open Systems Interconnection (OSI) model.
Common examples are Transmission Control Protocol (TCP), which provides acknowledge and retry mechanisms to ensure successful transmission of data, and Rate Control Protocol (RCP). RCP is a member of the IP set that provides packet ordering and timing information relating to the source data being carried in the packet, allowing a solution to be engineered around the limitations of Ethernet.
All of this makes networks a viable option for the distribution of video, and there are technologies that provide an equivalent solution to the crosspoint router for video.
Today, crosspoint routers are still significantly cheaper than a network equivalent, but there are already applications where a hybrid of the two approaches are being used. Typically, the network will provide connectivity over the wide area, with crosspoint routers providing local switching at the network nodes.
So crosspoint routing technology is not dead, but we need to rethink. Historically these switches have been the most economical solution for handling demanding television applications. However, the reduction in cost of network bandwidths means that a network may become a viable alternative.
A nice black box with a row of RJ45 telecomms sockets alongside another row of BNC connectors may sound like the obvious way forward. But this is unlikely to be developed for years, if ever. One problem is flexibility: How many would you specify of each? Another is how you would then deal with legacy systems, and especially distributed router infrastructure.
A more practical system would separate the decision making from the execution. In other words, required tasks would be monitored from a central unit, which would then designate these to different equipment as appropriate.
The idea is to link together cross-point and software-directed signals with a control and command center. The benefit of this hybrid approach is that if a direct link from A to Z fails, it could be dynamically rerouted from A to P, P to T and T to Z. Such flexibility is already happening in specific island installations, but not in a manner that satisfactorily bridges the different worlds of files and video signals.
An important part of all this is that the method of conveyance must be abstracted away from the user, as the last thing we want to do is burden operators with an additional layer of complexity. Far from it in fact, the system must be capable of selecting the best means of signal conveyance in a manner that is completely transparent to the user.
Of course the days when routers were little more than an electronic jackfield have long gone, with the best systems now offering A-to-D/D-to-A and digital format conversion within the router itself.
What we need to do next is consolidate the benefits of both crosspoint and network technology within the same system, and further integrate the roles of routing with automation systems.
Neil Maycock is chief marketing officer at Pro-Bel.
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