By Olivier Suard, Vice President of Marketing, Nevion
Considered less expensive over time than broadcast-specific baseband technology, IP can also make use of existing technology and infrastructure. To many this is a big advantage, eliminating the need for major upheaval.
So far so good; except that this approach can significantly limit IP’s great potential. Unfortunately, encouraged by some IP switch vendors, operators sometimes fall into the trap of focusing on products. The initial focus should be on getting the network architecture and the control right for broadcast applications and workflows.
Today, three main architecture layouts are used in broadcasting and other industries.
Centralized star network
This approach is consistent with the traditional baseband architecture — all connections transit through a large IP router that is located in the master control room (MCR). However, this means there is no signal aggregation at the edge: everything needs to travel to the central router. Fibers must be laid to connect every single device to the central router.
To cater for the highest demand and anticipate future needs, broadcasters often purchase an oversized router from the outset. Capacity is often reached sooner than anticipated, which then necessitates the replacement of the central router.
Also, every connected device occupies one expensive high-bandwidth port on the central router, regardless of actual bandwidth requirement. This makes the cost-per-port for low bandwidth devices high. The lack of aggregation means redundancy needs to be handled by the edge devices.
Finally, a star network architecture is not inherently suitable for treating remote locations as extensions of the main location, as it assumes all traffic will transit through the central router.
Star networks may appear at first to be simple and convenient, but in practice are highly-limiting, potentially vulnerable and likely to be expensive.
Large data centers often use an established distributed IP network approach, known as a spine-leaf architecture. This involves two or more routers at the core (spine) and other smaller routers at the edge (leaf).
By connecting all the equipment in each area to aggregating leaf routers, and then connecting these to the main routers, broadcasters reduce the number of connections going directly to the main routers, leading to simplified fiber management. Fewer fibers also mean fewer ports are needed on the central router(s), and a more effective cost-per-port, especially for low bandwidth devices.
The spine-leaf architecture makes it easy to build redundancy into the network for all devices at a much lower cost. This approach also provides optimal flexibility and scalability. Capacity can be increased by adding leaf or spine routers, rather than replacing existing ones wholesale – as is the case with star networks. This also means that networks don’t need to be oversized from the outset – capacity can be added over time.
While the layout of a true spine-leaf architecture can be more complex than other approaches, it is a scalable, resilient and high-performance network structure perfectly suited to the needs of broadcasters.
This third architecture model is what some might call a spine-leaf, but in reality, it is a ‘dual star’ architecture model. While it still involves the use of two spine routers, each leaf in the network is only connected to one of the spines.
This solution is not flexible when it comes to load distribution and optimization of total network capacity. As the network evolves, it puts special requirements on end devices that need redundant connections.
The proponents of this architecture usually favor automatic protocol-based routing rather than Software Defined Networking (SDN). While a pseudo spine-leaf might be initially more appealing due to the simplicity in configuring it, only a true spine-leaf architecture enables broadcasters to get the most out of their IP infrastructure investment in their facilities.
In tandem with the network architecture, operators also need to orchestrate and control the IP media network:
The protocols that typical IP switches run (e.g. IGMP/PIM) enable the network elements to make decisions about routing based on the IP traffic. This means the decision of how to transport individual media flows across the network can be left to the network, rather than the operator.
While widely used in IP networks, automatic routing has disadvantages when it comes to professional real-time media production networks.
For example, automatic routing may not be fast enough to deliver the significant number of simultaneous switching events required in live production. It can also get into trouble with networks where loops exist and bandwidth management can be poor.
Most of these problems can be overcome by IP network experts, but their help will be needed every time there is a significant change in configuration, for example, new studios added or large number of cameras moved from one location to another.
Software Defined Network routing
SDN puts routing control in the hands of a centralized control layer. The management and orchestration software holds a complete view of the available equipment, the network infrastructure and the services both those in place today and those planned. Thanks to this, it can efficiently make intelligent decisions on routing and controlling flows. It can also provide the explicit routing capability that broadcasters expect and need.
SDN also guarantees a higher level of performance when compared to automatic routing. The software is also in control of every media flow, which means it is more aware of, and better at dealing with, existing and even planned bandwidth requirements. It is even beneficial from a protection and security perspective. The orchestration and control software can easily create path diversity to protect failures, and can also fully control which destination is allowed to receive which multicast from a given source, thereby reducing security risk.
Unlike automated routing, SDN can, with the right orchestration and control software, easily handle any network architecture without compromise.
Broadcasters should be architecting the network using a true spine-leaf model, and controlling the elements within it using SDN routing. It is the most effective way of squeezing as much potential out of IP technology as possible, in turn helping deliver optimal return on investment and higher chances of operational success.