Broadband ISDN bandwidth efficiency in the support of ISO connectionless network service

A major data application of broadband ISDN (B-ISDN) is the interconnection of LANs over a wide area, by using a switched multi-megabit data service (SMDS). The bandwidth efficiency of SMDS/B-ISDN in supporting ISO connectionless network service is examined. The B-ISDN cell header and the functions related to cell segmentation/reassembly together consume about 17% of the available bandwidth, thereby leaving at most 83% for the higher layers. Network address information also constitutes a significant portion of the protocol control information in sending each transport protocol data unit (TPDU) by using ISO´s connectionless network protocol over SMDS/B-ISDN. Depending on the TPDU size used, the overall efficiency can range from about 30% (for a TPDU size of about 100 octets) to about 80% (for a TPDU size of 2000 octets or more)