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 <htmldeveloper@xxxxxxxxx> 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.
