One document matched: draft-ohta-notasip-01.txt

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INTERNET DRAFT                                             Masataka Ohta
draft-ohta-notasip-01.txt                  Tokyo Institute of Technology
                                                          Kenji Fujikawa
                                                        Kyoto University
                                                           10 April 1998


          Nothing Other Than a Simple Internet Phone (NOTASIP)


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).


Abstract

   This memo describes a simple protocol for Internet phone without QoS
   guarantee.


1. The architectural Principle of the Internet Phone

   Fortunately enough, Internet is the install base of data
   communication that other network technologies must find someway to
   interoperate with the Internet to survive a little longer.

   However, in the world of phone communication today, POTS is the
   install base. For the Internet to replace POTS within a few years, it
   is important that Internet phone interoperates with POTS.

   So, the primary requirement to the Internet phone at this early stage
   is that it should be able to interoperate with a dumb analog phone,
   which constitutes the install base.



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INTERNET DRAFT                   NOTASIP                      March 1998


   Historically, telephone companies in different nations tried hard to
   make their system not to interoperate smoothly to protect their
   market. None the less, or as a result, protocols to interoperate POTS
   is well developed. The protocols must be constructed over voice, the
   only common transport over different phone systems.  A notable
   protocol is operator assisted call. However, as human intervention
   costs a lot, most POTS support tone dialing capability for the least
   digital communication capability.

   Note that complex capabilities of digital phones, which is
   disappearing, have nothing to do with the install base and are
   ignored in this memo.

   Possible complex capabilities of Internet phone such as multiparty
   teleconferencing, which is hard to operate over voice, are also
   ignored in this memo.  It should be noted that there is multiparty
   teleconferencing service already available through POTS, simulation
   of which over the Internet phone is not difficult without complex
   Internet protocol.

   POTS is the install base worth considering. As it is difficult for
   human being to generate or recognize IP packets over POTS with voice
   or dial tones, protocols needs complex exchange of IP packets should
   be considered seriously only after we don't have to interoperate with
   POTS,

   It is assumed that the operating system support a notion of connected
   UDP socket [UNIX].


2. Caller Initiate the Call

   The caller host somehow (through SDP URL [SDP, SDPURL] of callee's
   home page, for example) finds the callee's IP address, UDP port
   number (with default port number of <to be assigned by IANA>) and
   desired encoding.

   The caller host opens a UDP socket and start sending properly encoded
   UDP packets of voice.


3. Callee Accept the Call

   The callee host receiving a UDP packet from someone opens a new
   connected UDP socket to the callers UDP port using a new source port
   number and the same IP address as the destination address of caller's
   packet.




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INTERNET DRAFT                   NOTASIP                      March 1998


   The callee host, then, start ringing the phone to notify the
   existence of a call to the callee person.  The ringing tone should
   also be sent to the caller.

   If the callee host do not want to accept simultaneous call, it may
   suspend the UDP port used to accept the call.  Then, if the port is
   already connected to someone else, ICMP error packet is returned,
   which makes the caller host generate a busy signal to the caller
   person.


4. Connection Established

   If the callee person holds up a headset, the callee host should send
   the voice of the callee person to the caller host.  The caller host
   receives a first packet and, confirming the source IP address of the
   packet is callee host's, connects its UDP port to the callee's
   sending port and the call is established.,


5. Call Termination

   To terminate the call, the caller or callee host close the socket.

   The same port number should not be used again until 256 (maximum IPv4
   TTL) + 30 seconds passes.


6. Interoperation with PSTN

   Interoperation with PSTN is performed over voice, the only common
   transport, with operator assistance, dial tone or anything.  The
   exact protocol over the voice is service provider dependent and MUST
   NOT be standardized. IETF MUST NOT define a standard on natural
   language messages to/from telephone operators nor calling card
   syntax.


7. Error Conditions

   If the connected UDP socket can not be created or the socket
   generates some error, the call terminates.

   If the caller host receives a UDP packet from someone other than the
   callee host before the call established, they should be ignored.

   If there is no packets received to a port for 30 seconds, the call
   terminates.



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INTERNET DRAFT                   NOTASIP                      March 1998


8. References


[SDP]    Mark Handley and Van Jacobson, "SDP: Session Description Proto-
         col," Internet Draft draft-ietf-mmusic-sdp-05.txt (work in
         progress), Nov 1997.


[SDPURL] (to appear)


[UNIX]   See UNIX manuals.


9. Security Considerations

   The security of POTS accounting is often based on 4 digit password or
   plain credit number and is quite poor.  Moreover, it is, in general,
   impossible to know the phone number of the caller. But these are the
   accepted security of the phone system.

   Best effort Internet phone is basically free (except for a flat rate
   portion) that no serious security consideration is necessary as a
   phone system.  A possible denial of service attack can be based on
   forged caller source IP address but is a lot more harmless than the
   similar attack with POTS.


Authors' Addresses

   Masataka Ohta
   Computer Center
   Tokyo Institute of Technology
   2-12-1, O-okayama, Meguro-ku, Tokyo 152, JAPAN
   Phone: +81-3-5734-3299
   Fax: +81-3-5734-3415
   EMail: mohta@necom830.hpcl.titech.ac.jp

   Kenji Fujikawa
   Faculty of Information Science
   Kyoto University
   Yoshidahonmachi, Sakyo Ku, Kyoto City, 606-01, JAPAN
   Phone: +81-75-753-5387
   Fax: +81-75-751-0482
   EMail: magician@kuis.kyoto-u.ac.jp






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