Performance comparison of native ATM vs IP over ATM

Abstract

engineers through its high bandwidth and multi traffic support. The robustness of the Internet Protocol (115 contributed to massive increase in Internet hosts globally. IP is a connectionless protocol as opposed to ATM, which is connection oriented. TCP, another connection oriented protocol, runs on top of IP in the Internet environment. Running TCP/IP over ATM results in redundant processing for two flow control mechanisms implemented by TCP and ATM. This redundancy can be eliminated by implementing ATM protocol in its Native Mode, where the application sends data directly to the ATM Adaptation layer through the ATM API, thereby bypassing the transport and network layers. The data transfer is then handled by the addressing scheme, signaling mechanism and routing protocols of ATM. The objective of the research was to compare performance of Classical IP over ATM and Native ATM for Constant Bit Rate (CBR) and Unspecified Bit Rate (UBR) traffic types. The parameters taken into consideration for performance comparison were throughput, per packet delay and packet loss. Experiments were carried out by initiating data transfer across two machines in the Distributed Systems Laboratory, which were connected through a single ATM switch using an OC-3c link. The experiments prove that Native ATM outperforms IP over ATM both in terms of throughput and delay. Maximum throughput for IP over ATM was achieved for a packet size of around 16000 bytes and maximum throughput for Native ATM was achieved for a packet size equal to the Maximum Transmission Unit (MTU), which for experiments was 9172 bytes. It was discovered that delay is smaller for Native ATM than for IP over ATM. Also, there was no appreciable packet loss involved in the data transfer.