re for identifying the users implemented as a point-to-point service, providing the of the AAL, assembling/disassembling the variable pay- transport of the contents of one network physical in- load associated with each individual user, error correc- terface to another physical network interface. This can tion, and the relationship with the SSCS. Each AAL2 prevent the implementation of some network topologies, user can select a given AAL-SAP associated with the QoS and can result in increased network cost. required to transport that individual higher-layer appli- cation. AAL2 makes use of the service provided by the Dynamic Bandwidth CES underlying ATM layer. Multiple AAL connections can be The limitations in CES resulted in the development of associated with a single ATM layer connection, allowing a new standard from the VTOA workgroup of the ATM multiplexing at the AAL layer. Forum, which is referred to as "Dynamic Bandwidth Circuit Emulation Services DB-CES." The objective of b) AAL2 Service-Specific Convergence this standard is to detect active or inactive timeslots of Sub-layer a legacy TDM trunk from a PBX or multiplexer SO that According to the recommendations of the ITU-T 1.363.2, inactive timeslots can be dropped from the next ATM the SSCS is defined as the link between the AAL2 CPS structure to allow you to use and reutilize this bandwidth and the higher-layer applications of the individual AAL2 for other services such as CBR, VBR, UBR, and ABR users. Several SSCS definitions that take advantage of the applications. AAL2 structure for various higher-layer applications are planned. A null SSCS, already understood and used in con- junction with the AAL2 CPS, satisfies most mobile voice ATM trunking of narrowband services applications. To satisfy higher-layer requirements associ- using AAL2 ated with data and AAL2 configuration messages-called AAL2 Negotiation Procedures, or ANP-an SSCS for The foregoing CES mechanisms treat voice as being segmentation/reassembly (temporarily called I.SEG) is in a constant 