TCP Probe: A TCP with built-in Path Capacity Estimation

Knowing the capacity of an Internet path is important for efficient network utilization, pricing, and management. Using the capacity information, one can provide better TCP congestion control, multimedia streaming, P2P peer selection, and overlay structuring. Capacity estimation has been extensively studied. Though current approaches have been able to provide fast and accurate capacity estimates, they are mostly “active” in nature (ie, they utilize extra probing packets) and thus tend to be intrusive. In this paper, we propose TCP Probe, a “passive” capacity estimation extension to TCP, to accurately estimate bottleneck link capacity of an Internet path. The TCP Probe extension is packet-pair based, and it is applicable to all TCP variants. Using simulation and Internet measurements, we show that TCP Probe is able to correctly measure bottleneck capacity of a path. Moreover, we present a simple application of TCP Probe where TCP is forced to enter slow start phase when a drastic capacity change from LOW to HIGH is detected. The results show that the capacity estimate provided by TCP Probe enables it to take better advantages of the capacity increase than the original TCP. In summary, TCP Probe is simple, passive, and accurate, and it is applicable to a broad variety of TCP variants. 1 2