Window Management Suggestions

Window Management Suggestions

      Allocating a very small window causes data to be transmitted in      many small segments when better performance is achieved using      fewer large segments.

      One suggestion for avoiding small windows is for the receiver to      defer updating a window until the additional allocation is at      least X percent of the maximum allocation possible for the      connection (where X might be 20 to 40).

      Another suggestion is for the sender to avoid sending smallsegments by waiting until the window is large enough before      sending data.  If the the user signals a push function then the      data must be sent even if it is a small segment.

      Note that the acknowledgments should not be delayed or unnecessary      retransmissions will result.  One strategy would be to send an      acknowledgment when a small segment arrives (with out updating the      window information), and then to send another acknowledgment with      new window information when the window is larger.

      The segment sent to probe a zero window may also begin a break up      of transmitted data into smaller and smaller segments.  If a      segment containing a single data octet sent to probe a zero window      is accepted, it consumes one octet of the window now available.      If the sending TCP simply sends as much as it can whenever the      window is non zero, the transmitted data will be broken into      alternating big and small segments.  As time goes on, occasional      pauses in the receiver making window allocation available will

           Specification

      result in breaking the big segments into a small and not quite so      big pair. And after a while the data transmission will be in      mostly small segments.

      The suggestion here is that the TCP implementations need to      actively attempt to combine small window allocations into larger      windows, since the mechanisms for managing the window tend to lead      to many small windows in the simplest minded implementations.