Why Use Satellite?
IP Multicast Technology

UPDATE HUNDREDS, OR THOUSANDS OF SITES IN ONE TRANSMISSION

In smaller networks, the way that Scala InfoChannel communicates between the Network Manager and Player is with standard Internet protocols such as FTP or with UNC paths. In larger networks, and especially with larger content such as MPEG2 files, standard FTP transmissions can be very inefficient - having each player pull its content individually from a central FTP server. Imagine 1,000 players each trying to pull 1 gigabyte of content from a single Network Manager server, more or less at the same time. That's a lot of data! In fact, your IT department might think that they were under a "denial of service attack" from this sort of job that amounts 1 terabyte of traffic.

Now imagine if you could communicate with those 1,000 Players by sending content JUST ONCE. That's the beauty of IP Multicast. And that's the beauty of Scala's software family; the same software architecture scales from 10 players to 10,000 players seamlessly. InfoChannel even supports a shared multicast delivery offering from Hughes Network Systems, which lets you "pay by the megabyte". This can be a very economical alternative to purchasing dedicated bandwidth for smaller multicast networks.

TECHNOLOGY OVERVIEW

Here's the bad news - the public Internet does not support IP Multicast. The good news is that most satellite providers DO support multicast, and in fact, prefer multicast transmissions. This paper will explain some of the terminology and hopefully de-mystify the technology for you.

As your digital signage network expands into hundreds or thousands of remote sites, it may become time to consider one of the four multicast technologies currently available. These are:

• Dedicated Satellite Multicast Bandwidth
• Shared Satellite Multicast Delivery
• Datacast (over-the-air terrestrial)
• Terrestrial IP Multicast

Scala supports each of these network technologies, along with the bevy of wired and wireless unicast technologies such as 802.11b, 802.11g, and standard hardwired CAT5 connections. Installing a 256Kbps Frame Relay connection or even a relatively cheap DSL circuit to each player location, assuming you can even get DSL service in all locations, can really add up when it comes to your monthly commutations bill. By using IP multicast technology on your 1,000-unit network, your price per site per month can be a fraction of a cheap DSL circuit and it has a ubiquitous footprint.

When it comes to large narrowcasting deployments, Scala's significant competitive advantage is that the InfoChannel 3 suite and its predecessor have both supported IP multicast for several years and new customers will not be the guinea pig by any stretch of the imagination. With over 15,000 units in the field and with multiple networks having over 1,000 players each, InfoChannel can administer any number of sites - whether it's 10 or 10,000 players.

There are four main ways to communicate via multicast. The most common is a dedicated satellite multicast subscription, which is supported by all major satellite bandwidth providers including Hughes Network Systems, Spacenet (Gilat), and GlobeComm.

Scala is a founding member of the Hughes Broadband Alliance, and as such, our software has specific support for Hughes' DIRECWAY® multicast delivery system. This program offers the smaller network to "pay by the megabyte". So if you have 200MB to send out once a week, dedicated bandwidth is probably a waste, but with Hughes, your costs can be significantly lower for the smaller network with infrequent, but larger updates. Most of our larger customers use this method today.

A third option is a relatively new offering provided by PBS National Datacast in the United States. This program uses spare bandwidth in digital television (HDTV) channels to transmit data via standard over the air broadcast antennas. For networks that need high bandwidth one way communications in major metropolitan areas, this can be a very interesting alternative. An HDTV channel has 19.4 Mbps throughput over the air. With today's variable bit rate encoders for video, there is often significant spare bandwidth (e.g. 6 Mbps) for other applications. This has been successfully tested with Scala InfoChannel at WHYY in Philadelphia.

A fourth alternative is terrestrial IP multicast. This is offered by many major ISPs and telecom companies such as AT&T, MCI/Worldcom, Sprint, and others. This is not very common, but if all of your locations are within the same "cloud", it is possible for the network operator to enable multicast data over your network.