Virtual channel connection
Virtual channel connections (VCC) offer the most flexibility to users. In a VCC environment, each conversation (voice, data, or video) is mapped to a unique virtual circuit. Each VCC has a single destination and contracted service class. The most commonly used ATM connection type, VCCs are purchased by small- to medium-sized customers for interconnectivity between locations.
Probably the most common use of ATM VCCs is LAN interconnection.
The visual shows routers interconnected using ATM VCCs. In this example, ATM provides full-mesh router connectivity. A VCC is established between each router, and LAN addresses are mapped to each VCC, enabling the routers to choose the appropriate VCC for each destination. For this environment, a similar class of service is assigned to all VCCs. Depending on traffic requirements and the number of users at each location, the access lines and traffic parameters might be different. To include Internet access as well as internal communications, additional VCCs could be created between the existing corporate routers and the ISP router (or routers).
This example illustrates the flexibility of VCCs. Each is provisioned separately, and each has its own service contract and user profile.
ATM-capable multimedia PBXs allow a corporation to use the ATM transport to carry voice and data traffic between the corporate office and carrier services. For each service type, a separate VCC is used between the PBX and the carrier network. Available from a host of vendors, integrated access devices consolidate services from a single platform. The visual shows an example application: the integrated access device is a PBX supporting multiple services.
The PBX consolidates these services for access to network resources. The voice traffic from traditional PBX functions are sent to the central office’s class 5 switch. The Internet traffic is passed to an ISP router. Video traffic is passed to another corporate location’s video conferencing suite. Each service is carried on a separate VCC, each with a separate destination and class of service. The single access line is sized to handle the consolidated traffic load.
Video on demand
In this application of the future, VCCs to video servers are established on demand for the duration of the video. The visual shows another application for VCCs.
A cable provider offers ATM service. The customer’s set-top device includes ATM functionality as well as normal television circuitry. When the customer wishes to view a movie, a VCC is established between the set-top box and a video server. Once the video is complete, the VCC is released. Depending on the underlying technology of the video server and the set-top box, the VCC could support constant rate service (the server provides streaming video) or guaranteed service (the video is downloaded to the set-top device).