Elephant Flow

An "elephant flow" is a term describing an extremely large (in total bytes) continuous flow set up by a TCP (or other protocol) flow measured over a network link. Elephant flows, though not numerous, can occupy a disproportionate share of the total bandwidth over a period of time. It is not clear who coined "elephant flow", but the term began occurring in published Internet network research in 2002 when the observations were made that a small number of flows dominate total Internet traffic (for example, Fang & Peterson). For example, researchers (Mori et al.) studied the traffic flows on several Japanese universities and research networks. At the WIDE network they found elephant flows were only 4.7% of all flows but occupied 41.3% of all data transmitted during the time period.

The actual impact of elephant flows on Internet traffic is still an area of research and debate. Some research shows that elephant flows may be highly correlated with traffic spikes and other elephant flows (Lan & Heidemann and Mori et al.). Elephant flows have varying definitions proposed by researchers including flows that occupy greater than 1% of total traffic in a time period (Estan), measuring the duration of the flow (Papagiannaki), and looking at flows whose size is greater than the mean plus three standard deviations of traffic during the time period (Lan). One of the main goals of research into elephant flows is to develop more efficient bandwidth management tools and predictive models for the Internet.

References

Estan, C. and Varghese, G. "New directions in trafficmeasurement and accounting," "Proceeding of ACMSIGCOMM Internet Measurement Workshop 2001,San Francisco Bay Area", Nov. 2001.

Fang, W., Peterson, L. "Inter-AS traffic patterns and their implications"Global Telecommunications Conference, GLOBECOM '99"3, Pages: 1859-1868.

Lan, K. and Heidemann, J. "On the correlation ofinternet flow characteristics." "Technical ReportISI-TR-574, USC/ISI", 2003.

Mori, T.; Kawahara, R.; Naito, S.; Goto, S., "On the characteristics of Internet traffic variability: spikes and elephants"Applications and the Internet, 2004. Proceedings. 2004 International Symposium on Applications and the Internet"Pages: 99 - 106

Papagiannaki, K., Taft, N., Bhattacharyya, S., Thiran, P., Salamatian, K., Diot, C., "A Pragmatic Definition of Elephants in InternetBackbone Traffic" "Proceedings of the 2nd ACM SIGCOMM Workshop on Internet measurement", Nov 2002 Pages: 175 - 176