d8d3d4b5   
   From: rick.jones2@hp.com   
      
   newbie123  wrote:   
   > Hi what is relationship between the congestion window, advertised   
   > window in TCP and TCP window size. I was believe that when   
   > connection is first setup the congestion window is how much can be   
   > sent in the first packet. once an ack is recvd than it gets   
   > incremented however in packet capture tool I see window size is   
   > mostly always constant even at start of connection. how can one side   
   > say that my window size (which is how much that host can receiv)is   
   > 65535 but in actuality it can only receive 1 segment size which is   
   > the receivers advertised window. thanks   
      
   The "effective" TCP window size will be the minimum of at least these   
   four things:   
      
   1) the receiver's advertised window - what you see in the window   
      field, perhaps scaled by the wscale option you might see on the   
      SYNchronize segments used to establish the connection. generally   
      related to the value for SO_RCVBUF in a get/setsockopt() call   
      
   2) the quantity of data the sending TCP can track for possible   
      retransmissions - a sending TCP must retain a reference to the data   
      it sends until it is ACKnowledged by the recieving TCP.  this does   
      not appear in a field in any headers sent on the wire   
      
   3) the sending TCP's computed value for the congestion window (cwnd) -   
      this is the quantity of data (or number of segments) that the   
      sending TCP reasonably believes can be sent into the network at one   
      time without triggering congestion and thus packet loss.  this does   
      not appear in a field in any headers sent on the wire.   
      
   4) the quantity of data the sending application is willing to send at   
      one time before it stops and waits for a response from the remote   
      application.   
      
   rick jones   
   --   
   The computing industry isn't as much a game of "Follow The Leader" as   
   it is one of "Ring Around the Rosy" or perhaps "Duck Duck Goose."   
                                                       - Rick Jones   
   these opinions are mine, all mine; HP might not want them anyway... :)   
   feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...   
      
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