[IP-SFS] AUTH48 - RFC 4824 <draft-ip-sfs-rfc-04.txt> Now Available
RFC Editor
rfc-editor at rfc-editor.org
Fri Mar 30 23:45:38 CEST 2007
Authors,
Please note that this is your opportunity to review and approve this
document for publication. Normally, we provide you with a minimum of
48 hours to review the text prior to publication. However, because of
the time constraints, we would appreciate your immediate feedback (or,
as soon as possible).
The edited document is attached. We have also attached a diff file
that highlights the differences between your submitted version -04 and
our edited version of the document. Please review the files and
let us know if there are any updates required. We intend to announce
this on 1 April 2007, so please reply as soon as possible.
Thank you.
RFC Editor
****IMPORTANT*****
Updated 2007/03/30
RFC AUTHOR(S):
--------------
This is your LAST CHANCE to make changes to your RFC to be:
draft-ip-sfs-rfc-04.txt, once the document is published as
an RFC we *WILL NOT* make any changes.
ATTENTION: The editing process occasionally introduces errors that
were not in the Internet Draft. Although the RFC Editor tries very
hard to catch all errors, proofreading the text at least twice, typos
can slip through. You, as an author of the RFC, are taking
responsibility for the correctness of the final product when you OK
publication. You should therefore proofread the entire RFC carefully
and without assumptions. Errors in RFCs last forever.
The document will NOT BE PUBLISHED until ALL of the authors listed in
the RFC have affirmed that the document is ready to be
published, as ALL of the authors are equally responsible for verifying
the documents readiness for publication.
** Please send us a list of suitable keywords for this document, over
and above those which appear in the title.
Frequently INCORRECT information includes
- Contact Information
- References (are they up to date)
- Section Numbers
(especially if you originally put the copyright somewhere
other than the VERY end of the document, or if you numbered
the "Status of the Memo" field)
Please send us the changes, *DO NOT* send a new document with the
changes made. (If we think that the changes might be more than
editorial we will contact the AD or the IESG to confirm that the
changes do not require review.)
Send us the changes in THIS format.
1)*** SECTION #'s*** [i.e. Section 5, 2nd paragraph]
2) the text you want changed,
3) the new correct text and
4) if the changes are spacing or indentation than please note
that.
FOR EXAMPLE:
Section 5.6, 3rd paragraph
OLD:
The quick brown fox jumped over the lazy dog.
NEW:
The quick brown dog jumps over the lazy fox.
^^^ ^ ^^^
If you have a whole paragraph to replace you do not need to use
the arrow to point out the differences
INTRODUCTION, 2nd paragraph
Replace OLD:
alsdfja;sldjf;lajsd;fljas;dlfj;
With NEW:
nv;alkjd;lsf;aoisj;ltjka;sldkjf
Spacing or indentation problems...
Section 10, 1st paragraph (remove spaces between bit
and of, add space after butter)
OLD:
Better botter bought a bit
of bitter butterMary mary quite contrary
NEW:
Better botter bought a bit of bitter butter
Mary mary quite contrary
This document will NOT be published until we receive agreement, from
ALL listed authors, that the document is ready for publication.
Thanks for your cooperation,
-RFC Editor
-------------- next part --------------
Network Working Group J. Hofmueller, Ed.
Request for Comments: 4824 A. Bachmann, Ed.
Category: Informational I. 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. Signal 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. States .....................................................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.
3. Protocol Discussion
IP-SFS adapts the standard SFSS to encode an alphabet of 16 signals
(flag patterns) to represent data values 0-15 (Section 3.2.1) and 9
signals to represent control functions (Section 3.2.2). With 16 data
signals, IP-SFS transmission is based upon 4-bit nibbles, two per
octet. Each of the signal patterns defined in Section 3.2 is called
an SFS.
3.1. IP-SFS Frame
IP datagrams are formatted into IP-SFS frames by adding IP-SFS
headers and trailers. Figure 2 shows the format of one IP-SFS frame.
The frame is delimited by a control SFS called FST (Frame Start) and
a control SFS called FEN (Frame End). It is composed of a series of
4-bit nibbles, one per SFS.
An IP datagram will be fragmented into multiple successive IP-SFS
frames if necessary. When an IP datagram is fragmented into N
frames, the first frame will be sent with frame number N-1, the
second with frame number N-2, ..., and the last with frame number 0.
0 1 2 3
+--------+--------+--------+--------+--------+
| FST |Protocol|CksumTyp|Frame No|Frame No|
+--------+--------+--------+--------+--------+
| |
// DATA Payload //
| |
+--------+--------+--------+--------+---------+
| CRC | CRC | CRC | CRC | FEN |
+--------+--------+--------+--------+---------+
Note that each field represents one SFS or 4 bits.
Figure 2: IP-SFS Frame Format
FST: Frame Start control SFS
Hofmueller, et al. Informational [Page 3]
RFC 4824 IP over SFSS April 2007
Protocol: 4 bits -- Internetwork-layer protocol code
0 None.
1 For IPv4.
2 For IPv6.
3 For IPv4 frame gzip-compressed.
4 For IPv6 frame gzip-compressed.
5...15 Reserved for future use.
CksumTyp: 4 bits (one data SFS) -- Checksum Type
0 none.
1 CCITT CRC 16 (polynomial: x^16 + x^12 + x^5+1).
2...15 Reserved for future use.
Frame No: 8 bits (2 data SFSs):
Frame number for fragmented IP datagram.
DATA: 0 to 510 data SFSs (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
Data signals and control signals are based upon standard SFS
encoding, as described by [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
3.2.1. IP-SFS Data Signals
Figure 3 illustrates the 16 SFSs used to transmit data frames over
the link. The illustrations show each SFS as seen from the receiving
side.
SFS 0 __0 \0 |0
/|| || || ||
/ \ / \ / \ / \
A B C D
IP-SFS 0x00 0x01 0x02 0x03
-----------------------------------------
SFS 0/ 0__ 0 __0
|| || ||\ /|
/ \ / \ / \ / \
E F G H
IP-SFS 0x04 0x05 0x06 0x07
-----------------------------------------
SFS \0 |0__ 0| 0/
/| | /| /|
/ \ / \ / \ / \
I J K L
IP-SFS 0x08 0x09 0x0A 0x0B
-----------------------------------------
SFS 0__ 0 _\0 __0|
/| /|\ | |
/ \ / \ / \ / \
M N O P
IP-SFS 0x0C 0x0D 0x0E 0x0F
Figure 3: IP-SFS Data Signals.
Hofmueller, et al. Informational [Page 5]
RFC 4824 IP over SFSS April 2007
3.2.2. IP-SFS Control Signals
Nine control signals are used to signal special IP-SFS conditions.
Their meanings are listed in Figure 4. The illustrations show each
SFS as seen from the receiving side.
SFS __0/ __0__ __0 \0|
| | |\ |
/ \ / \ / \ / \
Q R S T
IP-SFS FST FEN SUN FUN
-----------------------------------------
SFS \0/ \0__ 0/_ 0/
| | | |\
/ \ / \ / \ / \
U V W X
IP-SFS ACK KAL NAK RTR
-----------------------------------------
SFS 0__ 0__
/| |\
/ \ / \
Y Z
IP-SFS RTT unused
-----------------------------------------
SFS _\0/_
/|\
/ \
Error
IP-SFS unused
Figure 4: IP-SFS Control Signals.
FST: Frame STart. Signals the start of a new frame.
FEN: Frame ENd. Signals the end of one frame.
SUN: Signal UNdo. Cancels the transmission of one or more individual
SFSs within the current frame. This signal will be
unacknowledged by the receiver.
Hofmueller, et al. Informational [Page 6]
RFC 4824 IP over SFSS April 2007
FUN: Frame UNdo. As long as Frame ENd is not sent, the transmitter
or the receiver may send a FUN to restart the transmission of
the current frame. This signal will be unacknowledged and may
be ignored by the receiver.
ACK: Frame ACK. Acknowledges reception of one frame.
KAL: KeepALive. Keep a connection alive. Is to be transmitted in
State Idle at a frequency of at least KAL_FREQ (see
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.
3.3. Protocol Limitations
Due to the physical characteristics of the transfer channel, bit
error rates are expected to be in the range of 1e-3 (boy scout) to
1e-4 (professional sailor), and also depend a number of physical
factors. Poor visibility due to weather conditions or lack of
illumination (e.g., night time) can drastically increase the error
rate.
IP-SFS provides no means to handle frame reordering or dual
(multiple) frame reception. Thus, the protocol is not suitable in
environments where interfaces are moving fast and/or when the path of
light is long.
3.4. Implementation Limitations
Maximum payload per frame: 510 SFS (0...510) nibbles (0 to 255
octets)
Maximum SFS per frame: 518
Maximum frames per session: 255 (0...254)
4. Interface Discussion
An interface is constructed through the participation of one or more
humans. A knowledge of the SFSS is recommended, but its absence can
be compensated by a well-designed GUI.
Hofmueller, et al. Informational [Page 7]
RFC 4824 IP over SFSS April 2007
4.1. Data Link Control
This section describes the control protocol used to allocate the
half-duplex data link to either interface.
Interfaces know three States: Idle, Transmitting (TX), and Receiving
(RX).
4.2. Establishing a Connection
IP-SFS is strictly point-to-point. Unless interface members are
acquainted with each other, a brief introduction of both sides is
suggested prior to setting up a link to reduce the likelihood of
interface-spoofing attacks.
Interfaces must agree on two different IP addresses on the same
subnet.
Interfaces are free to negotiate any period of time as TIMEOUT.
Possible values for TIMEOUT are the time it takes to smoke a
cigarette or the time it takes to drink a glass of water. If
negotiation fails, TIMEOUT defaults to 60 seconds.
The same procedure may be applied for the KeepALive FReQuency
(KAL_FRQ). The period of KAL_FRQ (1/KAL_FRQ) should be at least
5*TIMEOUT.
4.3. State Idle
Interfaces in State Idle must be ready to send an IP datagram
provided by a local higher-level protocol or to receive a datagram
from the link-partner. Interfaces in State Idle must send keep-alive
signals KAL at a frequency of at least KAL_FRQ.
There are no further definitions for State Idle, but we recommend
staying away from alcoholic beverages or other types of drugs that
could lead to an increased number of FUN and/or SUN signals, a
decrease in bandwidth, or an increase of line latency.
If the number of IP datagrams in the transmission queue is >0, the
interface may try to initiate a session by sending an RTT to the link
partner. If the link partner ready to receive, it returns an RTR
signal.
4.4. Session Initiation
An interface receiving a datagram from an Internet layer protocol
level may start signaling RTT.
Hofmueller, et al. Informational [Page 8]
RFC 4824 IP over SFSS April 2007
If the link partner does not respond with RTR within TIMEOUT, or the
link partner responds with RTT, the interface switches to State Idle
for a random period of time between 2 seconds and TIMEOUT, before
resending the RTT.
If the link partner transmits RTR, the interface transmits the number
of IP-SFS frames to be transmitted in this session as two SFSs
followed by another RTT. If the link partner does not transmit the
same number of IP-SFS frames followed by RTR within 3*TIMEOUT, the
interface switches to State Idle.
If the link partner transmits the same number of IP-SFS frames
followed by RTR, the interface switches to State Transmitting.
Unless obstructed through environmental noise or great distance,
hollering can be used to request line discipline from the link
partner in State Idle. The use of cellphones is also an option,
whereas throwing objects or using guns is not recommended, since it
could result in interface damage or destruction. This would be
counterproductive.
4.5. State Transmitting
Transmission of one IP-SFS frame starts with FST. After FST and
before FEN have been transmitted, the interface may acknowledge a
received FUN and restart the transmission of the active frame or
discard the signal and continue transmission of the active IP-SFS
frame.
If an error occurs by transmitting a wrong data SFS, the interface
may invalidate the last data SFS by transmitting SUN followed by the
correct signal. A series of incorrectly transmitted data SFSs may be
invalidated by sending a SUN for each invalid SFS, effectively back-
spacing the sequence.
Control SFSs cannot be invalidated.
If an error occurs, the interface may also transmit FUN and restart
transmission of the active IP-SFS frame.
Whether the interfaces choses SUN or FUN for error correction is up
to the interface, but it is suggested to use SUN for a single invalid
SFS, and FUN whenever the interface failed to transmit several SFSs
in a row.
After FEN has been transmitted, the transmitting interface waits for
the link partner to transmit ACK or NAK.
Hofmueller, et al. Informational [Page 9]
RFC 4824 IP over SFSS April 2007
If ACK has been received, the transmitting interface removes the
active frame and starts transmitting the next IP-SFS frame. If no
frames are left, the interface switches to State Idle.
If NAK has been received, the transmission failed, and the interface
must start transmitting the active frame again.
If the link partner does not transmit ACK or NAK within TIMEOUT, the
transmission failed, and the interface must start retransmitting the
active IP-SFS frame.
If transmission of the same IP-SFS frame fails 5 times, the interface
leaves the IP datagram in the transmission queue and switches to
State Idle.
4.6. State Receiving
In State Receiving, the interface stores each SFS received from the
link partner in the receiving queue in the order of appearance.
After FST and before FEN have been received, the interface may
transmit FUN at any time to request a retransmission of the entire
IP-SFS frame.
If the time between two received SFSs exceeds TIMEOUT, the receiving
interface must discard all data from the active IP-SFS frame and may
additionally transmit FUN. If the link partner does not continue
transmitting within a second TIMEOUT period, the interface must clear
the receiving queue and switch to State Idle.
If the interface receives SUN from the link partner, it must discard
the last received data SFS (if any). If N SUNs are received in a
row, then the last N data SFS must be discarded, unless there are no
more data SFS in the frame. If there are no more data SFS in the
frame to be discarded, the SUN signal must be ignored by the
interface.
If the receiving interface receives FUN from the link partner, it is
free to discard the frame received thus far. We suggest honoring FUN
since discarding the signal will decrease bandwidth.
After FEN has been received, the receiving interface evaluates the
checksum. If the checksum is good, the interface transmits ACK. If
the Frame Number of the active frame is 0, the interface passes the
entire data from the receiving queue to the higher level protocol,
clears the receiving queue, and switches to State Idle.
If the checksum is incorrect, the interface transmits NAK.
Hofmueller, et al. Informational [Page 10]
RFC 4824 IP over SFSS April 2007
4.7. Terminating a Connection
If the interface is in State Idle and the link partner did not
transmit any kind of SFS for at least five times 1/KAL_FRQ, the
connection is terminated and the interfaces are free to disband.
4.8. Further Remarks
Interfaces are connected to computer hardware by means of a suitable
input device (RX) and a suitable output device (TX). Possible
devices include keyboard, mouse, and monitor. Other means of
connection are subject to availability and budget.
Although it is theoretically possible to combine the TX and RX parts
of an interface in one human being, we suggest dividing the
operations among at least two people per interface. For longer
transmissions (multimedia streaming, video conferencing, etc.),
consider rotating and providing substitutes.
Bandwidth tends to vary. Typically TX starts at about 2-4 bits/s and
will decrease over time due to exhaustion and lack of concentration.
When an interface in TX State signals at a rate higher than the RX
interface is able to receive, signal loss occurs.
5. Security Considerations
By its nature of line-of-sight signaling, IP-SFS is considered
insecure. The transmission of sensitive data over IP-SFS is strongly
discouraged unless security is provided by higher level protocols.
Interfaces tend to keep data in their memory. There is no way to
determine the lifetime of data in memory. As a side effect, data
might show up in unwanted locations at undesired times.
We are currently not aware of a technique to reliably delete data
from interfaces' memory without permanent interface destruction.
6. Acknowledgements
We thank Eva Ursprung and Doris Jauk-Hinz from Womyn's Art Support
(WAS), Anita Hofer, Reni Hofmueller, Ulla Klopf, Nicole Pruckermayr,
Manfred Rittler, and Martin Schitter, and Bob Braden for all their
contributions and support of this project.
Hofmueller, et al. Informational [Page 11]
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 at mur.at
Aaron Bachmann (editor)
Ulmgasse 14 C
Graz 8053
AT
EMail: ip-sfs at mur.at
Iohannes Zmoelnig (editor)
Goethestrasse 9
Graz 8010
AT
EMail: ip-sfs at mur.at
Hofmueller, et al. Informational [Page 12]
RFC 4824 IP over SFSS April 2007
Full Copyright Statement
Copyright (C) The IETF Trust (2007).
This document is subject to the rights, licenses and restrictions
contained in 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 at ietf.org.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
Hofmueller, et al. Informational [Page 13]
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.mur.at/pipermail/ip-sfs/attachments/20070330/29cdd636/attachment.html
More information about the IP-SFS
mailing list