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• Sender & receiver negotiate
on window size
• In the figure below the sender
sends 2K data and the initial seq no
• The receiver sends the ack for
the next seq no it is expecting and also advertises
the widow size
• Suppose the window is zero then
sender waits and then sends a probe and then
sends the next set of data
• The diagram shows how the two
sides communicate
• Suppose there is only one byte
to be sent the 41 byte packet to be sent instead Nagle algorithm suggest that
when the first byte comes it is sent and the other buffered till the ack
received and then send the rest and wait for the ack and like this a sufficient
no of bytes go in one segment
Silly window
syndrome
At the receiver side even if a
byte available at its buffer it advertised and the sender sends
the buffer is full the sender
waits again and probes to get the window size so this will
continue and a loop formed to
avoid this the receiver is forced to wait till good amount of
buffer space availability and
then advertises and avoids the loop.
TCP Congestion
control
Congestion:
• informally: “too many sources
sending too much data too fast for network to
handle”
• different from flow control!
• manifestations:
– lost packets (buffer overflow
at routers)
– long delays (queueing in router
buffers)
Problems when
congestion happens
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