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. Masataka Ohta Expires on 9 October 1998 [Page 1] 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 ) 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. Masataka Ohta Expires on 9 October 1998 [Page 2] 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. Masataka Ohta Expires on 9 October 1998 [Page 3] 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 Masataka Ohta Expires on 9 October 1998 [Page 4]