Ethernet alternative makes streaming video affordable
June 18, 1999
(IDG) -- WideBand Gigabit Networking hasn't generated much buzz, but backers of the LAN technology say its quality-of-service (QoS) features and low cost meet a market need that neither ATM, Fibre Channel nor Gigabit Ethernet can satisfy.
WideBand provides 1G bit/sec aggregate throughput with guaranteed QoS over Category 5 copper wiring. It was invented by Roger Billings in the early 1990s, when he was president of the International Academy of Science in Independence, Mo.
High-speed routers were too expensive for many organizations at the time, so Billings developed WideBand technology as an affordable way to boost Ethernet performance. He wanted to provide an inexpensive platform for schools and other low-budget operations to experiment with multicast video.
Billings founded WideBand Corp. in 1994 and the firm began shipping products in 1996. The vendor's WideBand products include network adapters and LAN concentrators, plus FiberLink modules for interconnecting WideBand components over fiber-optic cable. WideBand Corp. also resells a variety of WideBand-enabled servers from WideNet Corp.
Compared with other gigabit technologies, WideBand is priced quite reasonably. A PCI network adapter from WideBand Corp. lists for $199, while a nine-port concentrator costs just $1,665. Contrast this with the 3Com Gigabit EtherLink Server network interface card's list price of $895, and the $6,395 cost of the 3Com SuperStack II Hub 1000 SX.
However, WideBand technology doesn't pose a threat to Gigabit Ethernet because few vendors aside from WideBand Corp. and WideNet manufacture WideBand adapters and concentrators. The brand equity of the Ethernet architecture is overwhelming, and the forthcoming standard for Gigabit Ethernet over copper may eventually eat into WideBand's cost advantage.
Under the covers
To network operating systems, WideBand looks just like Ethernet, with standard IEEE 802.3 packets and addresses. But when an operating system hands a packet to the WideBand driver for output, the driver adds a special WideBand header. On input, the driver removes the header and returns the packet to Ethernet format. Thus, Ethernet users can reap the benefits of WideBand without changing their software or twisted-pair wiring.
Like Ethernet, WideBand uses a star topology, but that's where the similarity ends. With Ethernet, end-stations share the physical medium. As an endstation puts a packet on the wire, it listens for collisions with packets sent by other endstations. If it hears a collision, it backs off and tries again later.
Ethernet collision detection may be effective, but it's not terribly efficient. A 10M bit/sec shared Ethernet LAN delivers only 4M to 5M bit/sec of usable throughput. The remaining bandwidth is spent on collision detection and back-offs.
While switches reduce the size of Ethernet collision domains, WideBand uses bandwidth more efficiently than Ethernet. Packets from different sources travel with very little space between them, and no bandwidth is wasted on false starts.
Each Category 5 cable between endstation and concentrator (essentially a switch) includes four twisted pairs. The first pair serves as a 267M bit/sec path from the endstation to the concentrator, while the second pair serves as a 267M bit/sec path in the opposite direction. Together, these pairs provide a full-duplex connection for ordinary client/server traffic. The third pair is a 267M bit/sec WideCast channel for delay-sensitive traffic, and the fourth pair is a control channel. (The actual bit rate of the client/server and WideCast channels is closer to 333M bit/sec, but 20% is lost to encoding overhead.)
Although WideBand doesn't allow for collisions on the wire, packets from two endstations can arrive at the concentrator simultaneously and compete for the input buffer. When this happens, the concentrator signals one of the senders to wait until the other is done. However, the 267M bit/sec makes the wait infinitesimal. With Ethernet, both senders have to back off and wait an arbitrary amount of time before they try again.
WideBand supports traffic prioritization on the client/server channels via a class-of-service identifier in each packet header. The network technology provides QoS by segregating delay-sensitive traffic and sending it over the WideCast channel. The WideCast channel can carry up to 170 MPEG-1 video streams simultaneously, says Paul Cherry, secretary of the WideBand Gigabit Networking Alliance (WGNA) steering committee and director of WideBand training at the International Academy of Science.
Formed in 1997 to promote WideBand technology, the WGNA has nearly 50 members. Cable manufacturers and academic institutions dominate the roster.
Cable manufacturers back WideBand because it's the ultimate stress test for Category 5 cable.
And schools have joined the WGNA because they're interested in affordable QoS. Northwest Missouri State University, for example, installed a three-building WideBand network about two years ago. The network supports video-based training and a video kiosk, among other bandwidth-intensive applications.
Jon Rickman, Northwest Missouri State's vice president for IS in Maryville, Mo., is impressed with WideBand's performance.
"It's so fast that you don't need to move anything, just access it across the WideBand net," he says. "It changes how you think about networking."
It is organizations such as Rickman's that WideBand vendors are targeting.
"We're aimed at schools and others who need video support but can't pay the big price," says Cherry. "We're not going head-to-head with the big guys for the business market."
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