Responses to Congestion

Tahoe TCP assumes a packet has been lost (due to congestion) when it observes NUMDUPACKS (defined in tcp.h, currently 3) duplicate ACKs, or when a retransmission timer expires. In either case, Tahoe TCP reacts by setting ssthresh_ to half of the current window size (the minimum of cwnd_ and window_) or 2, whichever is larger. It then initializes cwnd_ back to the value of windowInit_. This will typically cause the TCP to enter slow-start.

Tom Henderson 2011-11-05