A novel approach to advanced asynchronous transfer mode for high-speed computer communication networks

The number of Internet users continues to increase due to the popularity of the WWW (World Wide Web). Intranets and extranets have also become very popular as they enable the efficient use of data within companies and enhance business processing speed. IP (Internet protocol) packets are used to realize most of these computer communication services. IP belongs to the network layer in the OSI reference model, so the transfer performance of IP is influenced by the technology used in the data link layer under the network layer. One communication technology for the data link layer is ATM (asynchronous transfer mode). ATM technology was researched and recommended for B-ISDN (broadband integrated services digital network). We have been tackling an Internet/intranet/extranet backbone system that offers high speed, high throughput, small delay and low cost by IP/MAC (media access control) over ATM. However we faced the problem that ATM does not completely suit IP packet and MAC frame transfer. For example, there is the “dead cell problem” in which the loss of even one of the ATM cells forming the IP packet causes the loss of the entire packet. There is also the “cell tax problem”, in which the overhead of ATM cells is much larger than those of other long distance transfer techniques. Perfect EPD (early packet discard) is impossible because there is no indication bit that means a cell includes the head or tail part of a datagram in the payload. Moreover, intelligent and effective application use is difficult because the cell header has few CLP (cell loss priority) bits. This paper describes the main problems of datagram transfer across existing ATM networks and details a new cell structure that solves these problems. Other issues relating to this remodelling of the existing cell structure are also examined