Hi Peter I think I didn't explain properly
my question is not about what it is slow-start but regarding where (if it) is specified that after filling the receive window, slow-start process has to start when packet loss has occurred (?) In the graph I sent as a link, fast-retransmit occurs, but afterwards I don't see fast-recovery but slow-start instead. am I right? Thanks On Sun, Nov 9, 2008 at 3:30 PM, Peter Teoh <[EMAIL PROTECTED]> wrote: > this is from the RFC > > http://www.faqs.org/rfcs/rfc2001.html > > (noticed how the sender/receiver window control the flow in different > ways): > > The algorithm to avoid this is called slow start. It operates by > observing that the rate at which new packets should be injected into > the network is the rate at which the acknowledgments are returned by > the other end. > > Slow start adds another window to the sender's TCP: the congestion > window, called "cwnd". When a new connection is established with a > host on another network, the congestion window is initialized to one > segment (i.e., the segment size announced by the other end, or the > default, typically 536 or 512). Each time an ACK is received, the > congestion window is increased by one segment. The sender can > transmit up to the minimum of the congestion window and the > advertised window. The congestion window is flow control imposed by > the sender, while the advertised window is flow control imposed by > the receiver. The former is based on the sender's assessment of > perceived network congestion; the latter is related to the amount of > available buffer space at the receiver for this connection. > > The sender starts by transmitting one segment and waiting for its > ACK. When that ACK is received, the congestion window is incremented > from one to two, and two segments can be sent. When each of those > two segments is acknowledged, the congestion window is increased to > four. This provides an exponential growth, although it is not > exactly exponential because the receiver may delay its ACKs, > typically sending one ACK for every two segments that it receives. >
