Interworking Functions Effect on Bandwidth Allocation for LAN-BISDN Interconnection

The interconnection of remote Local Area Networks (LANs) through an Asynchronous Transfer Mode (ATM) based Broadband Integrated Services Digital Network (BISDN) is considered as an imminent interworking application. Major aspects to be considered regarding this application are processing speed of the interworking unit (IWU) for mapping LAN frames to ATM cells and ATM bandwidth allocation for LAN traffic transfer. In this paper we show that these factors are highly correlated. Through an accurate LAN user model, we quantify bandwidth and buffer requirements for the LAN-BISDN interconnection application, taking into account the smoothing effect in the LAN traffic injected in BISDN by the inter-working functionality. This becomes more emphatic under time-consuming, low-cost, firmware-based implementations of the interworking protocols, which however are not bottle-necks in the context of the interconnection of low-speed existing LANs with BISDN.