Exploiting Flow Relationships to Improve the Performance of Distributed Applications

Shang, Hao

Etd

Exploiting Flow Relationships to Improve the Performance of Distributed Applications

Público

Application performance continues to be an issue even with increased Internet bandwidth. There are many reasons for poor application performance including unpredictable network conditions, long round trip times, inadequate transmission mechanisms, or less than optimal application designs. In this work, we propose to exploit flow relationships as a general means to improve Internet application performance. We define a relationship to exist between two flows if the flows exhibit temporal proximity within the same scope, where a scope may either be between two hosts or between two clusters of hosts. Temporal proximity can either be in parallel or near-term sequential. As part of this work, we first observe that flow relationships are plentiful and they can be exploited to improve application performance. Second, we establish a framework on possible techniques to exploit flow relationships. In this framework, we summarize the improvements that can be brought by these techniques into several types and also use a taxonomy to break Internet applications into different categories based on their traffic characteristics and performance concerns. This approach allows us to investigate how a technique helps a group of applications rather than a particular one. Finally, we investigate several specific techniques under the framework and use them to illustrate how flow relationships are exploited to achieve a variety of improvements. We propose and evaluate a list of techniques including piggybacking related domain names, data piggybacking, enhanced TCP ACKs, packet aggregation, and critical packet piggybacking. We use them as examples to show how particular flow relationships can be used to improve applications in different ways such as reducing round trips, providing better quality of information, reducing the total number of packets, and avoiding timeouts. Results show that the technique of piggybacking related domain names can significantly reduce local cache misses and also reduce the same number of domain name messages. The data piggybacking technique can provide packet-efficient throughput in the reverse direction of a TCP connection without sacrificing forward throughput. The enhanced ACK approach provides more detailed and complete information about the state of the forward direction that could be used by a TCP implementation to obtain better throughput under different network conditions. Results for packet aggregation show only a marginal gain of packet savings due to the current traffic patterns. Finally, results for critical packet piggybacking demonstrate a big potential in using related flows to send duplicate copies to protect performance-critical packets from loss.

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