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Versions: 00 01                                                         
Network Working Group                                       T. Tornkvist
INTERNET-DRAFT                                           SERC, Melbourne
Expires in six months                                  10 September 1998
<draft-tornkvist-pop3-00.txt>

                                Abstract

   This memo describes an optional extension to the Post Office Protocol
   version 3 (POP3), which introduces a possibility for a POP3 client to
   be notified by  a  POP3  server  whenever  the  clients  maildrop  is
   accessed.

Status of this Memo

   This document is  an  Internet-Draft.   Internet-Drafts  are  working
   documents  of  the Internet Engineering Task Force (IETF), its areas,
   and its working groups.  Note that other groups may  also  distribute
   working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and  may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate  to  use  Internet-  Drafts  as  reference
   material or to cite them other than as "work in progress."

   To view the entire list of current Internet-Drafts, please check  the
   "1id-abstracts.txt"  listing  contained in the Internet-Drafts Shadow
   Directories  on  ftp.is.co.za   (Africa),   ftp.nordu.net   (Northern
   Europe),  ftp.nis.garr.it  (Southern  Europe), munnari.oz.au (Pacific
   Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast).

Table of Contents

   1. Introduction ................................................    1
   2. Operation ...................................................    2
   3. NTFY sent by the client .....................................    2
   4. NTFY sent by the server .....................................    3
   5. Alteration to the RSET command ..............................    3
   6. Alteration to the UPDATE state ..............................    4
   7. Author's address ............................................    4


1. Introduction

   The Post Office Protocol version 3, as described in RFC  1939,  is  a
   simple  and  low-cost method of enabling mail access. The host making
   use of the POP3 service is referred to here as the "client", and  the
   host  providing  the  service as the "server". When a client wants to
   retrieve mail from a server he establish  a  TCP  connection  to  the



Tornkvist                                                       [Page 1]


INTERNET DRAFT    Notification - An extension to POP3  10 September 1998


   server  and  then uses various POP3 commands to access the mail-drop.
   Thus every time a client wants to check for new mail he has  to  poll
   the  server.  For a mail-drop which seldom receives new mails this is
   obvious not economical.  It  may  also  be  a  security  issue  since
   repeated  attempts  to  access  the  server  are  more  vulnerable to
   interception. This memo tries  to  remedy  this  by  introducing  the
   concept  of  notification.   This  memo  describes  how  a client can
   request that the server notify the client when any changes have  been
   made to the clients mail-drop.

2. Operation

   A new POP3 command named NTFY is added. It is used both by the client
   and  the  server. When a client wants to be notified by the server he
   sends a NTFY command together with a host name and port number.  When
   the  client's  mail-drop  has  been modified the server establishes a
   connection to the specified host name and port  number.   The  server
   begin  by  sending a NTFY command together with the name of the mail-
   drop.  After  this  both  the  client  and  the  server   enter   the
   AUTHORIZATION  state,  as described in RFC 1939. Thus, the client has
   to continue the exchange of commands  to  identify  and  authenticate
   itself accordingly.

   As soon as a server tries to establish a TCP connection  to  be  used
   for  notification,  it also removes the request for notification.  It
   is up to the client to issue a new NTFY command if  he  wants  to  be
   notified  again.  The  client  can only issue the NTFY command in the
   TRANSACTION state.

   A request for notification will  not  be  activated  until  the  POP3
   session  enters  the UPDATE state. During the TRANSACTION state it is
   possible to cancel the request for notification  by  using  the  RSET
   command.

3. NTFY sent by the client

   This command can only be sent when the client is in  the  TRANSACTION
   state.

      NTFY hostname port-number

         Arguments:
             a hostname argument that fully specifies the host
             to where the notification shall be delivered, and
             a port number to be used

         Restrictions:
             may only be given in the TRANSACTION state



Tornkvist                                                       [Page 2]


INTERNET DRAFT    Notification - An extension to POP3  10 September 1998


         Discussion:
             The POP3 server issues a positive response if requests
             for notification can be serviced. However, the request
             for notification will not be valid until the POP3
             session enters the UPDATE state.

         Possible Responses:
             +OK
             -ERR

         Examples:
             C: NTFY campari.rmit.edu.au 9411
             S: +OK

4. NTFY sent by the server

   When a client is to be notified about changes made to his  mail-drop,
   the  server establish a TCP connection to the specified host and port
   number. As soon this is done, the request for notification is  erased
   from  the  server.  This  is done regardless of if the connection was
   successful or not.

      NTFY name [timestamp]

         Arguments:
             a name specifying the mail-drop in question and
             an optional timestamp if APOP authentication
             is to be used

         Restrictions:
             only one attempt to contact the client will be made

         Discussion:
             As soon the server has sent this command, both the
             client and the server are supposed to enter the
             AUTHORIZATION state.

         Examples:
             S: NTFY pop5432 <1896.697170952@campari.rmit.edu.au>

5. Alteration to the RSET command

   A server which support this  extension  shall  erase  a  request  for
   notification as a result to the RSET command.

6. Alteration to the UPDATE state

   A server which has received a request for notification shall not make



Tornkvist                                                       [Page 3]


INTERNET DRAFT    Notification - An extension to POP3  10 September 1998


   it valid until the UPDATE state has been entered.

7. Author's address

   Torbjorn Tornkvist
   SERC (Software Engineering Research Center)
   110 Victoria St, Carlton
   Victoria 3053
   AUSTRALIA

   Phone: +61 3 9925 4089
   Fax:   +61 3 9925 4094
   Email: tobbe@serc.rmit.edu.au






































Tornkvist                                                       [Page 4]