The differences between IP and ATM raise three issues. First is the question of how Internet applications can take advantage of ATM quality of service facilities, without support from other portions of the Internet. A second issue is that of determining which IP conversations should be multiplexed onto a single ATM virtual circuit. Last is the problem of virtual circuit management, which determines when ATM connections should be established and torn down.
We have examined different quality of service, multiplexing, and virtual circuit management policies, and evaluated their relative merits from the standpoint of the performance of typical Internet applications. Our evaluation used a simulation of a large IP internetwork with a wide-area ATM backbone and a synthetic workload modeling the traffic generated by common Internet applications. For this purpose, we implemented a new network simulator, the Internet Simulated ATM Networking Environment (INSANE).
Our results show that the use of different scheduling algorithms and QOS parameters can be used to express preference for certain applications, although some care must be taken to avoid starvation effects. The use of jitter controlling schedulers in the ATM network can be efficacious in reducing packet loss in long TCP bulk transfers. We see that multiplexing can improve application performance due to a reduced need to set up ATM virtual circuits, although interactions with some network service disciplines can negate these effects. Finally, we show that caching idle virtual circuits for reuse is, in general, beneficial for both network and application performance.