The Transmission of IP Datagrams over the Semaphore Flag Signaling System (SFSS)
RFC 4824

Document Type RFC - Informational (April 2007; Errata)
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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

   This document specifies IP-SFS, a method for the encapsulation and
   transmission of IPv4/IPv6 packets over the Semaphore Flag Signaling
   System (SFSS).  The SFSS is an internationally recognized alphabetic
   communication system based upon the waving of a pair of hand-held
   flags [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

   Link:    A link consists of two (2) interfaces that share a common
            subnet.

   Link Partner:
            The opposite interface.

   Session: The transmission of an entire IP datagram.

Hofmueller, et al.           Informational                      [Page 2]
RFC 4824                      IP over SFSS                    April 2007

   SFS:     One Semaphore Flag Signal, i.e., one flag pattern (Section
            3.2).

   SFSS:    The Semaphore Flag Signaling System.

   IP-SFS:  IP over Semaphore Flag Signaling System.
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