Traffic Characteristics of Bulk Data Transfer using TCP/IP over Gigabit Ethernet

As network data rates scale-up, an understanding of how and why traffic characteristics change is needed. We study the characteristics of bulk data transfer TCP/IP flows in a fully-switched Gigabit Ethernet network. Both disk-to-disk and memory-to-memory transfers are studied. We investigate flow characteristics as a function of link speed, server load, operating system (Linux and WindowsNT), and number of simultaneous clients accessing a server. Using trace-based simulations, we find that there is great variability in the “friendliness” of a flow to a single-server queue in terms of packet losses. Flows on Gigabit Ethernet tend to cause greater packet losses for a given link utilization and buffer size under certain conditions. We also find some unexplained inefficiencies in some of the flows. We investigate methods of application-level traffic smoothing to improve flow characteristics. A prototype packet-spacing socket send function is developed to reduce packet losses.