Topics in TCP
TCP Congestion Control
If the receiver advertises a large window-size , larger than what the
network en route can handle , then there will invariably be packet
losses. So there will be re-transmissions as well . However , the sender
cannot send all the packets for which ACK has not been received because
this way it will be causing even more congestion in the network.
Moreover , the sender at this point of time cannot be sure about how
many packets have actually been lost . It might be that this is the
only one that has been lost , and some following it have actually been
received and buffered by the receiver. In that case , the sender will
have unnecessarily sent a number of packets.
So the re-transmission of the packets also follows slow-start mechanism.
However , we do indeed need to keep an upper bound on the size of the
packets as it increases in slow start, to prevent it from increasing
unbounded and causing congestion. This cap is put at half the value of
the segment size at which packet loss started.
Congestion Window