In the previous post, I discussed the huge potential power savings being enabled by the IEEE’s 802.1-az Ethernet specification now under development and early deployment. While IEEE 802.1-az promises to save significant amounts of power and energy through the use of sleep modes for inactive Ethernet ports, continuous stream-based multimedia applications of the various Ethernet standards cannot endure power-down and wake-up delays associated with the new specification. Consequently, the IEEE is also developing new standards to help Ethernet connections better handle these multimedia applications. But before discussing those new standards, it’s helpful to step back and take a look at the current state of multimedia networking because it closely resembles the networking situation with computers if you set your personal time machine to take you back in time by 30 years or so. (No DeLorean needed!)
Three decades ago, computer networking was in chaos. Each of the major mainframe and minicomputer vendors had a unique and mutually incompatible networking scheme. The electronics didn’t match. The bit rates didn’t match. The packetizing and de-packetizing schemes didn’t match. The error-detection and –correction schemes didn’t match. And just as important, the cables and connectors didn’t match. Any data center than supported hardware from multiple computer vendors needed a big box of cables with all sorts of connectors just to handle the incompatible networking schemes.
Chances are good that you have a similar box of cables at home to help you connect all of your multimedia devices together. I know I can connect one of my televisions with an RF coax cable, simple audio and video coax cables terminated with RCA plugs, RCA RGB component cables, or HDMI cables. My audio connections include simple RCA-plug audio cables, coaxial and optical TOSlink cables, and speaker wire without connectors. I do indeed have boxes full of AV cables that no longer match any of the AV components I now use. Worst of all, these are all dumb, dumb, dumb connections. The AV system components have no idea what’s coming over these cables. I need to configure each box (usually through a remote control I can’t find) to tell it which of the many back-panel ports to use for the audio and video signals and how the streamed information is encoded. For example, I need to manually tell my system which of the DVD audio streams to use while watching a video. You would think that reasonably good equipment would be able to detect and optimize the experience automatically, but my equipment can’t.
So it’s not much of a reach to envision a world where Ethernet-enabled AV equipment automagically discovers the abilities of the other equipment in a local AV network cloud and then collaborates with the other connected equipment to optimize each viewing or listening experience. That end is precisely the goal of the IEEE 802.1 AVB (audio video bridging) working groups. However, the goals go much farther than that. Imagine AV systems with multiple content sources and multiple listeners. Then imagine a network of AV components that can automatically optimize the listening and viewing experience for each AV network user simultaneously in real time. That scenario is also within the goals of the 802.1 AVB efforts. Part of the need is for components to discover the capabilities of other Ethernet-connected devices in the local AV component cloud. Part of the need is to reserve a substantial part of the cloud’s networking bandwidth for content streams that absolutely require low-latency, high-bandwidth content delivery.
This effort relies on three interwoven specifications:
- IEEE 802.1-AS – A timing synchronization standard
- IEEE 802.1-Qat – A stream-reservation protocol
- IEEE 802.1-Qav – A packet forwarding and queuing protocol that can accommodate isochronous and non-isochronous AV traffic using reserved bandwidth and regular data-type Ethernet traffic using best-effort packet delivery.
Together with the Energy Efficient Ethernet specification (802.1-az) discussed in the previous blog entry (even AV components sleep sometimes), the IEEE 802.1 AVB specifications ensure even longer life for the Ethernet protocol, now going on its fourth decade of ever-widening deployment.
