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From: dhp@ihnp3.UUCP (Douglas H. Price)
Newsgroups: net.unix-wizards,net.lan
Subject: Re: STREAMS query
Message-ID: <174@ihnp3.UUCP>
Date: Tue, 15-Oct-85 12:34:14 EDT
Article-I.D.: ihnp3.174
Posted: Tue Oct 15 12:34:14 1985
Date-Received: Thu, 17-Oct-85 00:32:30 EDT
References: <471@enmasse.UUCP> <1699@brl-tgr.ARPA> <449@cheviot.uucp> <169@ihnp3.UUCP> <739@cyb-eng.UUCP>
Reply-To: dhp@ihnp3.UUCP (45262-Douglas H. Price)
Distribution: net
Organization: ATT Bell Labs
Lines: 46
Keywords: streams datagram virtual circuit Ritchie terminology
Xref: watmath net.unix-wizards:15265 net.lan:1094
Summary: terminology problems


>> There is no requirement that STREAMs must implement a virtual circuit.
>> -- 
>> 						Douglas H. Price
>
>Could you please state YOUR definition of a stream and of a virtual circuit?
>-- 
>  /  \    Bill Crews
> ( bc )   Cyb Systems, Inc
>  \__/    Austin, Texas
>

The term "STREAMs" refers to Ritchie streams.  A Ritchie stream is normally 
implemented as a local-kernel-only virtual circuit with a device on your host.
The virtual circuit is not required to have any expression in the network, or
on the remote end of the communication.

Given the general confusion concerning the term "stream", it might be argued
that another name should have been chosen for this particular mechanism.  But
that's the name that was chosen, so I had thought it understood that in its
capitalized form "STREAMs", it could be distinguished from the more general
bytestream paradigm.  Sorry about the confusion.

On to the definitions:  A "virtual circuit" is a full-duplex, errorless
communications path possessing the properties of non-duplication, non-loss and
strictly serial (ordered) data.

A "datagram" is an atomic, self-contained message, normally completely contained
in a single outbound packet for which there is no guarantee of delivery
(i.e., send and pray).

A "stream" (bytestream) series of bytes which exhibit no natural boundaries on
messages.  Message boundaries (if any) are implicit in the data of the bytestream
and are understood at the peer-to-peer level rather than at the transport level.

"STREAMs" (Ritchie streams) are a kernel mechanism for implementing the insertion
of  protocols in between a user process and the device associated with the
communication.  

 

-- 
						Douglas H. Price
						Analysts International Corp.
						@ AT&T Bell Laboratories
						..!ihnp4!ihnp3!dhp