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RE: Nature of Application Protocols!

From: Martin Duerst <duerst@w3.org>
Date: Fri, 30 Aug 2002 11:36:27 +0900
Message-Id: <4.2.0.58.J.20020830113130.0259e150@localhost>
To: "Naresh Agarwal" <nagarwal@in.firstrain.com>, <ietf-http-wg@w3.org>

At 14:31 02/08/29 +0530, Naresh Agarwal wrote:
>Hi Martin,
>
>Can you elaborate, why SMTP is Push?
>
>First, let me tell you, what i think of Push and Pull.
>Please correct me, if i'm wrong.
>
>Pull: You make a request to fetch some data (Request-Response)
>Push: You receive some data, without making a request. (No Request, Only 
>Response)
>
>In case of SMTP, data, i.e, mails are pushed to SMTP servers.
>But finally, one've to use POP/IMAP to fetch the mails.
>
>Don't this mean that SMTP is pull rather than push?

Please don't mix up SMTP and 'Internet mail'. SMTP is push, and stateful.
'Internet mail' is a 'protocol' (in the sense that it is a
collection of conventions for communication) consisting of
several actual protocols at layer 7. 'Internet mail' as a whole
may be called stateless (there are states at a still higher level,
in that mails get identified as replies to other mails,...).
'Internet mail' as a whole requires both pull and push
(if only one is done, the email won't reach the recipient),
and therefore cannot be called either 'pull' or 'push'.


Regards,    Martin.



>thanks,
>regards,
>Naresh Agarwal
>
> > -----Original Message-----
> > From: Martin Duerst [mailto:duerst@w3.org]
> > Sent: Thursday, August 29, 2002 2:18 PM
> > To: Naresh Agarwal; ietf-http-wg@w3.org
> > Subject: RE: Nature of Application Protocols!
> >
> >
> >
> > Well, SMTP is definitely push. FTP can be used both ways.
> > Roughly upload = push, download = pull.     Martin.
> >
> > At 14:08 02/08/29 +0530, Naresh Agarwal wrote:
> >
> > >I'm sorry..it was a typo error...
> > >
> > >i meant to say that -
> > >
> > >HTTP, FTP, SMTP, POP, IMAP etc. are "Syncronous",
> > "Connection Less" and
> > >"Pull" in nature.
> > >
> > >regards,
> > >Naresh Agarwal
> > >
> > > > -----Original Message-----
> > > > From: Martin Duerst [mailto:duerst@w3.org]
> > > > Sent: Thursday, August 29, 2002 1:27 PM
> > > > To: Naresh Agarwal; ietf-http-wg@w3.org
> > > > Subject: Re: Nature of Application Protocols!
> > > >
> > > >
> > > >
> > > > HTTP is synchonous, but very much pull, not push.
> > > >
> > > > Regards,    Martin.
> > > >
> > > >
> > > > At 12:39 02/08/29 +0530, Naresh Agarwal wrote:
> > > >
> > > > >Hi
> > > > >
> > > > >I have some general questions regarding protocols.
> > > > >
> > > > >Every application protocol is -
> > > > >
> > > > >1)Synchronous or Asynchrnous
> > > > >2)Connection Less or Connection Oriented
> > > > >3)Push or Pull
> > > > >
> > > > >My understanding is that most of the protocols - HTTP, FTP,
> > > > SMTP, POP,
> > > > >IMAP etc. are "Syncronous", "Connection Less" and "Push"
> > in nature.
> > > > >
> > > > >I could not find any protocol, which is widely used and is
> > > > Asynchronus,
> > > > >Connection Oriented and Pull in nature!
> > > > >
> > > > >Am i right or i'm missing something?
> > > > >
> > > > >Also does Synchrony and Pull, Asynchrony and Push are
> > > > synonyms..i.e every
> > > > >Synchronous protocol is Push and every Asynchronous protocol
> > > > is Push..?
> > > > >
> > > > >Can somebody provide me with the explanation of above (if
> > > > possible, with
> > > > >examples)?
> > > > >
> > > > >thanks,
> > > > >regards,
> > > > >Naresh Agarwal
> > > >
> > > >
> >
> >
Received on Friday, 30 August 2002 00:51:36 GMT

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