INFORMATIONAL

Errata Exist

Network Working Group J. Hofmueller, Ed. Request for Comments: 4824 A. Bachmann, Ed. Category: Informational IO. zmoelnig, Ed. 1 April 2007 The Transmission of IP Datagrams over the Semaphore Flag Signaling System (SFSS) Status of This Memo This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract This document specifies a method for encapsulating and transmitting IPv4/IPv6 packets over the Semaphore Flag Signal System (SFSS). Table of Contents 1. Introduction ....................................................2 2. Definitions .....................................................2 3. Protocol Discussion .............................................3 3.1. IP-SFS Frame Description ...................................3 3.2. SFS Coding .................................................4 3.3. IP-SFS Data Signals ........................................5 3.4. IP-SFS Control Signals .....................................6 3.5. Protocol Limitations .......................................7 3.6. Implementation Limitations .................................7 4. Interface Discussion ............................................7 4.1. Data Link Control ..........................................8 4.2. Establishing a Connection ..................................8 4.3. State Idle .................................................8 4.4. Session Initiation .........................................8 4.5. State Transmitting .........................................9 4.6. State Receiving ...........................................10 4.7. Terminating a Connection ..................................11 4.8. Further Remarks ...........................................11 5. Security Considerations ........................................11 6. Acknowledgements ...............................................11 7. References .....................................................12 Hofmueller, et al. Informational [Page 1]

RFC 4824 IP over SFSS April 2007 1 . Introduction JCroft, Wikipedia]. Under the SFSS, each alphabetic character or control signal is indicated by a particular flag pattern, called a Semaphore Flag Signal (SFS). IP-SFS provides reliable transmission of IP datagrams over a half- duplex channel between two interfaces. At the physical layer, SFSS uses optical transmission, normally through the atmosphere using solar illumination and line-of-sight photonics. A control protocol (Section 4) allows each interface to contend for transmission on the common channel. This specification defines only unicast transmission. Broadcast is theoretically possible, but there are some physical restrictions on channel direction dispersion. This is a topic for future study. The diagram in Figure 1 illustrates the place of the SFSS in the Internet protocol hierarchy. +-----+ +-----+ +-----+ | TCP | | UDP | ... | | Host Layer +-----+ +-----+ +-----+ | | | +-------------------------------+ | Internet Protocol & ICMP | Internet Layer +-------------------------------+ | +-------------------------------+ | SFSS | Link Layer +-------------------------------+ Figure 1: Protocol Relationships 2 . Definitions Hofmueller, et al. Informational [Page 2]

RFC 4824 IP over SFSS April 2007 Section 3.2.1) representing 0 to 255 octets of payload. CRC: 16 bits as four data SFSs. CRC checksum. Preset to 0xFFFF. One's complement of checksum is transmitted. FEN: Frame ENd control SFS. The number of transmitted SFSs per minute (Spm) depends on the experience of participating interfaces. Resulting link speed in bits per second for IP-SFS is (Spm/60)*4, not counting framing overhead. 3.2 . SFS Coding JCroft], [Wikipedia], and other sources on the Internet. The 16 data signals are interpreted as 4-bit nibbles, while the 9 control signals are used for data link control. IP-SFS defines the 16 data signals by the original SFSS encodings for letters A to P and the 9 control signals represented by SFSS encodings Q to X. Hofmueller, et al. Informational [Page 4]

RFC 4824 IP over SFSS April 2007 3.3 . IP-SFS Data Signals Hofmueller, et al. Informational [Page 5]

RFC 4824 IP over SFSS April 2007 3.4 . IP-SFS Control Signals Hofmueller, et al. Informational [Page 6]

RFC 4824 IP over SFSS April 2007 Section 4.2). This signal will be unacknowledged. NAK: Frame No AcK. The frame received is incorrect. RTR: Ready To Receive. Receiver acknowledges it is ready to receive. RTT: Ready To Transmit. Sender requests permission to initiate transmission. 3.5 . Protocol Limitations 3.6 . Implementation Limitations 4 . Interface Discussion Hofmueller, et al. Informational [Page 7]

RFC 4824 IP over SFSS April 2007 4.5 . State Transmitting Hofmueller, et al. Informational [Page 9]

RFC 4824 IP over SFSS April 2007 4.6 . State Receiving Hofmueller, et al. Informational [Page 10]

RFC 4824 IP over SFSS April 2007 7 . References JCroft] Croft, J., "Semaphore Flag Signalling System", <http://www.anbg.gov.au/flags/semaphore.html>. [Wikipedia] Wikipedia, "Modern semaphore", <http:// en.wikipedia.org/wiki/Semaphore#Modern_semaphore>. Authors' Addresses Jogi Hofmueller (editor) Brockmanngasse 65 Graz 8010 AT EMail: ip-sfs@mur.at Aaron Bachmann (editor) Ulmgasse 14 C Graz 8053 AT EMail: ip-sfs@mur.at IOhannes zmoelnig (editor) Goethestrasse 9 Graz 8010 AT EMail: ip-sfs@mur.at Hofmueller, et al. Informational [Page 12]

RFC 4824 IP over SFSS April 2007 BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Hofmueller, et al. Informational [Page 13]