Two major approaches for providing connectionless service for ATM networks are connection based and server based. In the connection based approach, the connection oriented service of ATM is used to interconnected pairs of ATM end systems. The end systems are then responsible for providing a connectionless service to various other end systems via ATM connections. In the server based approach, connectionless servers in the ATM networks directly provide a connectionless service. An end system may send all its packets to one connectionless server where each packet is individually routed to other connectionless servers en route to the destination. This paper examines analytically the resource requirements for these two approaches. Specifically, it finds the number of ATM connections, connection set-up rate and required number of connectionless servers.

It is crucial for ATM to efficiently support existing data applications. One of the promising methods of supporting data over ATM uses connectionless servers providing a packet switching service in the ATM network. There are two primary methods for forwarding cell based datagrams in a connectionless server: reassembly mode, where the datagrams are reconstructed before forwarding, and streaming mode, where each cell is forwarded as it arrives. The two modes impact the packet loss probability at a connectionless server, the packet delay, the interleaving method used, the AAL used, and the buffer space required. This paper investigates the performance of two forwarding modes. Extensive simulations show that forwarding connectionless packets in streaming mode is shown to result in lower packet loss and end-to-end delay than reassembly mode.

The advent of high speed, wide area ATM networks introducs a "backwards compatibility" dilemma. While emerging ATM networks must be capable of transporting future applications such as digital voice and video, many of the design choices made to optimize ATM for voice and video make the transport of traditional data traffic difficult. This paper will address some of these issues and propose possible solutions. This paper presents a promising method of providing connectionless service by buidling a virtual connectionless network on top of a public ATM network with a subset of the switches acting as connectionless servers. This method provides low transfer delay and low cost to the user.

The transport of connectionless data is necessary for the compatibility of emerging wide area ATM networks with existing computer networks. This paper investigates the design and performance of a virtual connectionless network overlayed on top of cell-based connection-oriented ATM networks. The virtual connectionless network is made possible by utilizing connectionless servers. Two packet forwarding techniques used by connectionless servers are examined. Forwarding connectionless packets in a cell-by-cell manner (streaming mode) is shown to result in lower packet loss and end-to-end delay than packet-by-packet forwarding of connectionless data (reassembly mode). A design and implementation are presented for a streaming mode connectionless server capable of a maximum throughput of 100 Mbps.