Data Transfer

After  connection  is established  bidirectional  data transfer  can take  place. The client  and  server  can both  send data  and acknowledgments. Figure  shows an example  in this example  after  connection is established  the client  sends 2000 bytes in two  segments. The  server  than send 2000bytes  in one  segment. The client   sends one more segment. The  first  three segments carry  both  data and  acknowledgment, but  the last segment  carries only an  acknowledgment because there are o more data to be sent. Note the value of the sequence and acknowledgment numbers. The data segments sent by  the client  have the PSH flag  set so  that the server TCP knows  to deliver data  to the server process as soon  as they  are received. The segment  from  the server on the  other hand does not  set the  push   flag. Most TCP implementation have  the options  to set  or not set  this flag.