FLIPPING THE SWITCH

Multicast versus VLAN switching in residential installs. Taft Stricklin, Just Add Power, Sales Team Manager, referees the results.

While multicast switching may not be the most glittering topic to cover in a world awash in high-speed technology, it’s importance can’t be dismissed. It’s a fundamental issue that residential installers shouldn’t overlook, as AV-over-IP video distribution has become the foundation of an infinite number of installations. We’re seeing smart homes of all sizes deploy a growing number of displays. These displays need to be connected to a variety of sources. As a result, integrators have become experienced in installing AV-over-IP systems utilising VLAN switching, reaping the benefits in both cost and labour. Now we’re seeing more interest in using IP multicast switching as an option, especially in large homes or multi-dwelling units (MDUs). The advantages of multicast have traditionally been enjoyed in the commercial AV sector and the broadcast industry, but this setup has an important place in the residential AV world as well. As such, the growing demand means that installers must develop more expertise and understanding of when multicast switching should be deployed versus VLAN switching.

THE DIRECT — VLAN AND SINGLE SWITCH CONFIGURATION

For many residential installs, a VLAN system is still the best option. Here, a canned driver communicates directly with the switch to route video traffic. The out of the box experience is simple. The best VLAN switches will isolate each video stream on the network, so there’s no sifting through packets and managing complex Internet Group Management Protocol (IGMP) membership messages that are necessary in a multicast setup. VLAN switching schemes usually switch faster because of the more controlled environment and there’s less likely to be network resource implications. For AV professionals, the plug-and-play nature of VLAN switching requires very little networking knowledge.

THE COMPLEX — MULTICAST AND THE NETWORK

Multicast switching operates differently. A multicast switch is responsible for communicating with every receiving device that wants to access the video stream and telling it what it should be doing. In more complex terms, receiving devices send an IGMP message, which tells the network which source they want information from. Those messages include a join message, which allows a device to subscribe to a multicast stream, and a leave message, which tells the switch to unsubscribe it from the stream. Source devices respond by sending data to the network only once, regardless of the number of subscribed receiving devices. The switch replicates the data so that each subscribed receiving devices gets a copy. The benefit is that this prevents unnecessarily burdening devices that do not need the data.

HOW AND WHEN TO DEPLOY VLAN VS MULTICAST

Multicast switching is a question of real estate versus resources. It opens up options so that AV and IT devices and sources can be comingled on the network. These situations are more prevalent in large home — over 25K sq ft — and MDU applications where more than one switch is required, and the network resources are available to support increased traffic on a network. There’s still a great outof-the-box experience, but deployment is more involved and complex. In some ways, it can be simpler, especially for if an IT pro is involved, because they can use a switch they’re already comfortable with and there are fewer requirements. The tradeoff, however, is that the installer is responsible for configuring it properly, which can be unfamiliar territory for residential AV integrators.

When selecting multicast switching, there are a few best practices to optimise the system for AV over IP video distribution. First, ensure that the switch selected has a high enough amount of bandwidth. Second, ensure it has enough PoE power to power all devices. Finally, it needs to have a large enough backplane bandwidth to manage all the video traffic.

CLOSING THE KNOWLEDGE GAP

From a manufacturing perspective, many companies are siloed and only offer multicast switching. In addition, most will have a very complex set of steps. However, with the right software and support, residential AV professionals can quickly train up to step through multicast scenarios for configuring drivers and automate the mundane IT/IP configuration portion. In this way it can be a bridge, allowing integrators a more organised and comfortable approach. For example, every display in each room can be named to match plans, blueprints, and control schematics. This makes it easier, and less time consuming for AV installers and ensures users can easily select and control source content for every screen — no matter how it’s happening on the AV-over-IP backend.