TM in the B- ISDN protocol stack, the ATM adaptation layer or AAL. Five types of AALs have been identified in the B-ISDN model. The key ones are packet switching service adaptation and circuit switching service adaptation. In adapting non time-sensitive traffic for transport, it is possible to segment large packets into smaller ones and route them to be reassembled sequentially. However, time-sensitive traffic (voice and video) is processed differently, using buffers to keep data flowing in a smoothly paced stream. When one ATM end-node needs to send data to another end-node, it requests a connection by transmitting a signaling request to the network. The network passes the requested path to the destination. If the destination node and the sender can negotiate a connection, a switched virtual circuit (SVC) is completed. When the devices are finished with their exchange, the SVC is taken down by all switching points originally engaged in setting it up. The sender also arranges end-to-end quality of service by specifying call attributes such as type and speed. As discussed previously, audio and video transmissions are time sensitive, but are adequate with some inaccuracy. Data transmissions, in contrast, require absolute accuracy-e.g. no absence of information-but are not time sensitive. Because ATM establishes connectivity through switching rather than through a shared bus, it offers dedicated bandwidth per connection, high aggregate bandwidth, and explicit connection procedures. ATM is, by definition, capable of providing isochronous service. End-nodes have a way of requesting specific network characteristics when they establish the call. For instance, a node can inform the network of the average bandwidth it will require and whether it will be bursting or sending Real-Time data. The network will condition a circuit based on this information. The network keeps a cumulative inventory of its bandwidth. As new requests for service arise, it decides, based on probabilities, whether it can service the new caller's req