Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!ucsd!ucbvax!SH.CS.NET!gwilliam
From: gwilliam@SH.CS.NET (George Williams)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Reliable Datagram ??? Protocols
Message-ID: <9010240209.AA12580@ucbvax.Berkeley.EDU>
Date: 23 Oct 90 18:15:49 GMT
References: <9010230140.AA07826@WLV.IMSD.CONTEL.COM>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 31

The "push" flag, present on tcp packets has nothing to do with
reliabilty. It just says ' forwards what's in the receiving 
application buffer ' up...now !

It has nothing to do with Datagram or Reliabilty but is associated 
with fragmentation and re-assembly.

Additionally, most APIs don't make this flag user accessible; as a 
good working knowledge of systems and protocol(s) as they pertain
to overall response time and throughput is assumed for those who
massage this flag. It can result in overall system degradation in
a distributed compute environment is set inappropriately..

A final word on UDP...if I may:

 () Architecturally, UDP is the connection-less transport for IP.

    Reliability as in pertains to delivery and retranmissions is 
    the assumed burden of  associated HLPs (higer level protocols)
    or service(s) present. I did not write the protocol but did 
    enough implementations to state this as fact.

 () It is generally the protocol of choice when the transmisssion
    media has a low error rate or an HLP (e.g. interactive ) that
    compensates for deficiencies.
    

   George Williams

( The above are my own humble views and opinions and are not a 
  critique )