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October 31, 2004 Provided by System Dynamics Inc.

Making Things Connect: The Digital Living Network Alliance

We've written many times about the need for ways that many kinds of media devices in the home can "talk" with each other over home networks. The Digital Living Network Alliance (DLNA) has been working on this for some time, and we will soon see the first devices based on their work.

We recently interviewed Scott Smyers, Chairman of the DLNA Board of Directors and a Vice President at Sony Electronics to find out how they were doing with the specifications and what kinds of products we would see.

We first wrote about the Digital Home Working Group (DHWG) a year ago--see Intel's Digital Home: Corporate Initiatives That Work ( )--and followed up a few months later in Setting Standards for Digital Media: DENi and DHWG ( ). Those articles described how leading companies from the PC, consumer electronics and mobile industries were working together to establish specifications for interoperable products in the digital home. They had established a goal of publishing their first set of guidelines during the first half of 2004, with products expected to reach the market in 2005.

In June, the group published its first guidelines, and changed its name to the Digital Living Network Alliance (DLNA), reflecting the change from a "working group" to an industry alliance. They say "Digital living encompasses the home and beyond".

Scott told us that the group had grown from its original membership of a few dozen companies to nearly 200. Its members include just about everybody in microelectronics, computers, consumer electronics and mobile. Companies are developing and starting to show products based on the initial guidelines, and we expect to see products at CES in January.

When we interviewed DLNA last January, we were struck by the absence of broadband. When we asked Scott about the role of broadband in DLNA, he said "Two devices should be able to interoperate, and be useful and usable -- even if you don't have broadband."

DLNA Guidelines

DLNA published its initial guidelines--DLNA Home Networked Device Interoperability Guidelines v1.0--in June. Scott told us about the rigorous process for formulating these guidelines: "Fifty to sixty engineers meet face-to-face once a month and teleconference every week."

The DLNA 1.0 guidelines ( ) establish an initial framework for interoperability between devices:

  • Network Connectivity: Ethernet and Wi-Fi (802.11a/b/g) provide physical connections between devices
  • Network Stack: IPv4 provides a foundation for applications to communicate over different networks
  • Media Transport: HTTP 1.0/1.1 is the baseline transport for media streaming
  • Device Discovery, Control and Media Management: UPnP Device Architecture 1.0 provides a way for devices to discover the presence and properties of other networked devices; UPnP AV 1.0 enables content to be identified, managed, distributed across all media devices
  • Media Formats: JPEG, LPCM, MPEG2 provide the interoperability baseline -- our earlier article Setting Standards for Digital Media: DENi and DHWG ( ) decribes how other media formats are supported.

The next set of guidelines (1.1) will define optional media formats such as GIF, MP3 and MPEG4 Part 10, and will add "smart remote" capabilities.

Scott said that several "plugfests" have already taken place to test products against these guidelines, and more are planned this year. He said the tools and the program for certification are in process, and we should see certified products with the DLNA logo by the second half of 2005.

Next Steps: DRM and "End-to-End QoS"

While the initial guidelines are a fine start, two critical pieces of the puzzle are still missing: digital rights management (DRM) and quality of service (QoS). Scott pointed out that by its rules "DLNA is constrained to take only already developed international standards" and these didn't yet exist for DRM and QoS.

DRM is very difficult since the content owners (especially the film studios) are reluctant to permit their content to move across a home network, for fear that it will get out of the home and into wide circulation--as has happened to music with "peer to peer" networking. QoS is less controversial, but DLNA requires standards to be set by other bodies before it can embrace them in its guidelines.

All home networking technology groups recognize the need for QoS standards. While data can be carried over a home network without QoS, media content such as voice, audio and video require QoS to preserve full quality, especially in a network used for multiple applications. Video will not work well on a network also used for data transfers and VoIP.

While everyone sees the need for QoS, engineers find it difficult to agree on how best to provide it. There are two main approaches:

  • "Prioritized QoS" operates by placing priority levels on packets used in different applications -- for example, high-definition video and voice might get the highest priority, standard-definition video the next priority, and data the lowest.
  • "Guaranteed QoS" operates by reserving bandwidth -- for example, once bandwidth has been reserved to support high-definition video, another high-definition video program could be rejected if there is insufficient bandwidth to support both simultaneously.

The IEEE has been working on wireless QoS standards for more than four years, considering both QoS approaches. The Wi-Fi Alliance recently adopted the "prioritized QoS" part of the draft 802.11e standard into the Wi-Fi specs as "Wi-Fi Multimedia" (WMM), and says it will include the full standard when it is completed. New technologies for home networking over existing power lines and phone lines also include QoS, as do emerging standards for high-speed personal area networking.

Cable and telephone companies have a strong interest in delivering streaming video content from their networks to home TVs. This requires "end-to-end QoS" starting from servers in their networks, delivered over cable or phone lines to a home gateway through cable or DSL modems, and carried from the gateway over a home network to a TV display.

Both CableLabs and the DSL Forum have worked to define appropriate QoS mechanisms for their networks. CableLabs defined QoS approaches for cable modems in its DOCSIS and PacketCable specifications, and for home networks in its CableHome 1.1 specifications. DSL Forum defined its QoS approach in TR059--see DSL Forum -- New Specs to Beat Cable ( ) for a description of its approach.

DLNA would appear to be the most promising forum to resolve the issue of end-to-end QoS. While the cable and telephone companies are unlikely to talk with each other about QoS issues, they are both likely to be willing to work with the PC and consumer electronics companies in the context of DLNA. Cablelabs is a member of DLNA. DSL Forum is not a member (its rules apparently don't provide a mechanism for membership), but Bell Canada--one of DSL Forum's key members--is.

We look forward to seeing agreement on common mechanisms for end-to-end QoS.

DLNA Products

At the CEATEC Japan conference held near Tokyo in early October, fifteen DLNA member companies showed prototypes and products designed to the DLNA guidelines. These included media servers, audio and video digital media adapters, networked DVD recorders and players, and many more. Atheros showed a wireless video networking solution based on its new AR5005VA chip, which we had seen when we visited Atheros in August - see 802.11a for Consumers: An Interview with Atheros Communications ( ).

Fujitsu, Kenwood, NEC, Panasonic, Sony and Toshiba all showed multiple prototypes and products at CEATEC. We take this as a good indication that the major consumer electronics companies are really committed to work toward common standards.

We expect to see these products and many more at CES in January. We'll have a full report in the January issue of our report.

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