Classroom without walls.

The idea of making ATM subordinate to the function of routing in LAN internetworks has resulted in a technology known as the switched router. One of the first school districts in the nation to recognize the power of the switched router was Hacienda La Puente Unified School District in City of Industry, Calif.

Based on an ATM Forum protocol development activity known as MPOA (multi-protocol over ATM), the switched router allows IP-based applications to run over ATM switches.

By taking advantage of ATM's scaleable bandwidth and quality of services (QoS) options, the switched router can support time-sensitive data delivery for applications that include video and voice.

The switched router dramatically reduces the cost of routing by leveraging an open architecture of ATM switches, MPOA-aware edge devices for Ethernet connections, and a centralized router server that assists in resolving IP to ATM addresses in the LAN. The result is applications-enabled networking.

Hacienda's view of networking was to break through barriers in the learning environment and make resources available wherever and whenever possible--a classroom without walls.

Being in the heart of Southern California's film and video industries, Hacienda needed a networking technology that could handle the demands of multimedia cost effectively.

The first phase of the Hacienda network project is underway, with a Newbridge Networks Vivid switched router deployed at Workman High School and several administrative sites. More than 1,000 servers and workstations are already connected to the network.

As early as 1987, Hacienda began deploying Ethernet local area networks to provide terminal interaction for administrative purposes. At that point, the idea of instructional computing or using networks to deliver educational material was very new.

The network and computer services team at Hacienda explored the possibility of providing academic computing solutions for areas outside of administration. That's when they ran into a technology wall.

"The limitations in network technology would not allow us to do the kind of things that we wanted to do," says Michael Droe, director of network and computer services.

"We fed the users a little bit--just enough to whet the appetite, but when they were really ready to start using networking applications seriously, there wasn't enough bandwidth or CPU power at the desktop to provide for the solutions they needed."

Hacienda started looking at broadband solutions, particularly ATM. "At the time, ISDN was starting to pick up speed, and ATM as a video component of broadband ISDN came to light in a number of scenarios," says Droe, "but the industry was still rather new at that point, so we had to make do with what was available."

Droe says the team became focused on multimedia networking--"not just data networks anymore, but the concept of moving video through the network while being able to utilize resources between classrooms, between buildings within a campus, and ultimately between different campuses within a school district."

Now Droe is well on his way to linking all sites with a fully meshed ATM fabric. Currently, the school district includes 40 primary sites and an additional seven sites supporting correctional education for greater Los Angeles County.

Hacienda's first major campus-wide switched routing initiative is taking place at Workman High School, with plans to use the model at other sites. While the Workman network supports traditional voice and data traffic, the most intensive traffic is generated by video and multimedia applications. Four video applications were deployed at the school last fall:

* Broadcast support for point-to-multipoint transmission. This allows office administrators to broadcast announcements directly to classrooms equipped with monitor receivers or computers, or both, that have MPEG video decoding devices.

* Real-time transport of video between the school's broadcast journalism news studio and a cable access channel Support for the popular broadcast journalism program is one of the reasons Workman High School was chosen as the first campus to be on the network. Students in the program produce a morning news show about school events.

The show used to be taped and the cassette sent to the community access cable channel that aired it later in the day. Now, using the ATM network and an MPEG video encoder, the program is transported in real time between the on-campus television studio to the cable access channel for rebroadcast to other sites.

* Desktop-to-desktop or desktop-to-classroom videoconferencing. This capability supports interactive distance learning applications in which multiple classrooms are linked to one instructor or a group of instructors or a group of students. It also supports staff development activities, collaborative student projects and, ultimately, distance learning to the home when adequate facilities are available through the public network.

* Video-on-demand or video retrieval. On-line access to full motion video will be available to support research projects, classroom learning experiences, and the broadcast journalism program.

With video playing such an important role in Hacienda's network plans, the school needed a partner knowledgeable in ATM transport, video applications, and data networking. It chose Newbridge.

"Switched routing brings routing intelligence into a switching architecture that makes the support of video over IP extremely efficient," says Droe. "In a traditional routing environment, the router has to analyze every packet, creating considerable overhead.

"In a switched routing network, the route server determines the path of the transmission, sets up a cut-through connection and then steps out of the way until either the transmission is finished and the connection is torn down, or another protocol is introduced into the stream."

At the heart of Hacienda's network is Newbridge's Vivid family of products based on a prestandard release of MPOA.

"I liked their approach because it made ATM subordinate to routing, which was my real problem when it came to multimedia apps," says Droe. "There is an advantage to having a centralized route server and not taking up processor cycles for route processing within the switches themselves.

"Some would argue that integrating route processing in every box makes the network completely plug and play," he continues, "but from a network management point of view, it's far easier to make changes to a single route server via a network manager than to change things on a box-by-box basis. We opted for centralized control."

Droe says he had to force himself to unlearn the limitations of routers and learn what switching could do.

"In a switched router it's a clean slate," he says." I can overlay a bridged network consisting of certain hosts and a routed network consisting of other hosts. I can mix and match port groups and protocols, and optimize VNETs for video. I've been able to make use of some very powerful VLAN capabilities from the start."

Hacienda La Puente School District's current network is based on six 36150 MainStreet ATMnet Access Switches in the backbone for transport between sites. The equipment and OC-3 connections are leased from GTE.

The high school campus and administrative facilities have a Vivid System Manager and Route Server, five Vivid ATM Workgroup Switches and 24 Vivid Yellow Ridges for access to the network for traffic originating on Ethernet segments.