Independent Submission T. Ritter
Request for Comments: 6217 1 April 2011
Category: Experimental
ISSN: 2070-1721
Regional Broadcast Using an Atmospheric Link Layer
Abstract
Broadcasting is a technology that has been largely discarded in favor
of technologies like multicast. This document builds on RFC 919 and
describes a more efficient routing mechanism for broadcast packets
destined for multiple Local Area Networks (LANs) or Metropolitan Area
Networks (MANs) using an alternative link layer. It significantly
reduces congestion on network equipment and does not require
additional physical infrastructure investment.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This is a contribution to the RFC Series, independently of any other
RFC stream. The RFC Editor has chosen to publish this document at
its discretion and makes no statement about its value for
implementation or deployment. Documents approved for publication by
the RFC Editor are not a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6217.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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to this document.
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Table of Contents
1. Introduction ....................................................2
2. Terminology .....................................................2
3. Limitations .....................................................2
4. Physical Layer ..................................................3
5. Frame Format in the OSI Model ...................................3
5.1. Data Link Layer ............................................3
5.2. Network Layer ..............................................3
5.3. Transport Layer ............................................4
6. Reception .......................................................6
7. Datagram Transmission ...........................................6
7.1. Chemical Approach to the Atmospheric Link Layer ............6
7.2. Location ...................................................7
7.3. Physical Layer Conditions ..................................7
8. References ......................................................8
8.1. Normative References .......................................8
8.2. Informative References .....................................8
1. Introduction
RFC 919 [1] defines a method for broadcasting packets to a local
network. It assumes that data link layers support efficient
broadcasting. In the years since RFC 919 was written, Local Area
Networks have grown exponentially in size, and frequently they are
not geographically local.
This RFC proposes a new data link layer that scales efficiently to a
geographically local network and, depending on visibility, to an
entire Metropolitan Area Network. By using a different transmission
medium, the broadcast traffic does not impact current inter- or
intra-network routed traffic. It also makes use of a widely
available infrastructure that is in use in all major cities and,
surprisingly, rural and under-developed locations as well.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119.
3. Limitations
This RFC does not propose solutions to all problems. Just as RFC 919
was unconcerned with reliability, we also do not guarantee that hosts
receive datagrams sent. Hosts may not receive packets for a variety
of reasons, among them weather conditions, line of sight, sleep
patterns, and distraction. A best-effort delivery approach is taken.
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These limitations do impact the usefulness of the proposal, but
organizations serious about distributing information in this fashion
can overcome these obstacles with relatively little difficulty.
4. Physical Layer
The physical layer used is made up primarily of nitrogen and oxygen,
at a pressure of 101.3 kilopascal at sea level, but dropping to about
half that pressure at operating altitudes. Microscopic residue or
trace elements may exist in the transmission medium, depending on
local formation properties.
This residue may include argon, carbon dioxide, neon, helium,
chloride anions, sulfur dioxide, and other molecules occurring at
very low mixtures. It is common for there to be some degree of
gaseous dihydrogen monoxide present. These trace molecules usually
do not impede the broadcast, although further details on datagram
transmission follow.
5. Frame Format in the OSI Model
It is always a challenge to design a protocol that allows enough
flexibility for future adaptation while keeping it efficient in size
-- and for this medium, size and complexity of the header are of
particular concern. For this reason, this RFC proposes
recommendations for the Data Link, Network, and Transport Layers.
Implementations MAY use any protocol that fits their needs for the
Network and Transport Layers. They SHOULD consider how different
protocols may be interpreted by recipients of the message and choose
the most effective protocol available. The protocols defined have
been designed to allow maximum ease of interpretation, so their use
is encouraged.
5.1. Data Link Layer
The Data Link Layer is primarily concerned with transmitting
datagrams between adjacent nodes, and it is unnecessary here since we
only support broadcast transmission. Implementers MUST NOT
encapsulate packets in a link layer protocol.
5.2. Network Layer
When designing a protocol for the Network Layer, it makes sense to
consider existing protocols in this layer and reference their
strengths and weaknesses. Looking at IPv4/6, we can see their header
structures include several fields unnecessary for our purposes:
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Destination, TTL (Time to Live), DSCP (Diffserv Code Point), ECN
(Explicit Congestion Notification), Hop Limits, and so on. We can
design a much more compact protocol thusly:
+-------------------------------+-----------------------------+
| Content | Source |
+-------------------------------+-----------------------------+
Figure 1: Layout of the Datagram
Content - A variable-length field containing the encapsulation of
higher-level protocols.
Source - The sender of the message. A transmission MUST choose one
of the following representations of the source:
- IPv4 address in dot-decimal notation (e.g., 192.168.1.1)
- IPv6 address in standard notation (RFC 5952 [2])
- telephone number in E.123 notation
- electronic mail address in E.123 notation
- Uniform Resource Identifier (RFC 3986 [3])
- geographic address
The Source field MUST be present -- to send a message anonymously, a
sender MUST use one of the reserved entries of the different types.
Reserved Entries for telephone numbers vary by region; for example,
in North America they are 555-0100 to 555-0199. Reserved entries for
IPv4 (RFC 5735 [4]), IPv6 (RFC 5156 [5]), and URIs (RFC 2606 [6]) may
be found in their respective RFCs. The concept of a region defined
by homogeneous communication characteristics has been put forward
already in [7], so geographic addressing ambiguities may be resolved
by community standards.
Because the message is sent to a specific geographical region, more
leniency is available in source addressing, but requirements may be
imposed by higher-level protocols.
We call this protocol the Asynchronous Dumb Visual Exchange of Raw
Transmissions or ADVERT.
5.3. Transport Layer
Similar to the Network Layer, a Transport Layer protocol is able to
omit several constructs that are used in existing Transport Layer
protocols. Consider TCP -- sequence, acknowledgement, and many of
the flags are discarded as there will be no SYN, SYN/ACK, or ACK
handshake in a broadcast message. Likewise, fields such as Window
Size and Urgent -- created primarily as a benefit to router
manufacturers -- are unnecessary in this medium.
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In fact, in the event of a plain text message, content SHOULD be
embedded directly in the ADVERT Protocol without the need of a
transport protocol. Consider the following packet:
Content Source
+------------------------------------------------------------+
| Lobster Dinner - only $14.99 500 Boardwalk, Pt Pleasant |
+------------------------------------------------------------+
Figure 2: Example ADVERT Datagram
For UTF-encoded payloads, one SHOULD use the default UTF-encoding so
the packet is human-readable. This will minimize accidental
misinterpretation. This transmission structure lends itself most
easily to human-parsable messages.
For messages intended to be responded to by a computer (for example,
binary content), a Transport Layer protocol MUST be used, and an
implementer SHOULD use UDP, as it is one of the more compact
protocols available in this layer. An implementer SHOULD encode the
UDP ports, length, and checksum in base-10 (leading zeros omitted)
and the data in Base64 encoding. The Base64 encoding, combined with
the UDP checksum, resolves ambiguities with trailing whitespace or
non-printable characters.
The usage of UDP or other protocols that compute a checksum over
source and destination addresses necessitates the use of either an
IPv4 or IPv6 address as the Source in the ADVERT Protocol. The
Destination address 255.255.255.255 MUST be used in the calculation
of an IPv4-based checksum, as it has already been specified as a
local hardware broadcast that must not be forwarded (RFC 919). For
IPv6, the All Nodes link-local multicast destination
FF02:0:0:0:0:0:0:1 MUST be used, defined in RFC 4291 [8].
ADVERT Datagram UDP Embedded Sample Data
+-----------------+ +--------+--------+ +--------+--------+
| | |Src Port|Dst Port| | 0 | 80 |
| | +--------+--------+ +--------+--------+
| | | Length |Checksum| | 24 | 62670 |
| UDP Packet | +--------+--------+ +--------+--------+
| | | | | R0VUIC8gSFRUUC8 |
| | | Data | | xLjENCg0K |
| | | | | |
+-----------------+ +-----------------+ +-----------------+
| Source Address | | Source Address | | 203.0.113.8 |
+-----------------+ +-----------------+ +-----------------+
Figure 3: Example of Encapsulating Binary Data in an ADVERT Datagram
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6. Reception
Upon receipt, the datagram should be optically scanned into an
electronically transmittable form, similar to the methods used in RFC
1149 [9]. If present, any checksums SHOULD be computed and compared
with supplied values. If the checksum does not match, the packet
MUST be discarded.
Physical layers always have advantages and disadvantages depending on
their condition, maintenance, prevalence, and economic factors; the
atmosphere is no different. The protocols defined herein do not
specify a TTL specifically because it is often out of their control,
and dependent on the conditions present. The intrinsic TTL produces
a curve of error rates where, after time, meaning cannot be
deciphered from the datagram either because of a non-matching
checksum or, in the absence of a checksum (such as the ADVERT
protocol), because of an unintelligible transmission. If the Source
field is sufficiently distinguishable, the recipient MAY contact the
sender for message clarification. RFC 919 is in agreement in stating
that broadcasts MUST NOT be assumed to have been reliably delivered.
Reconsidering Figure 3, a broadcast HTTP Request is sent, and
recipients should return the request from each of their computer
systems that are listening on the requisite port. It is important to
remember the security implications of the systems' acceptance of data
from unknown senders. It is the responsibility of each organization
to utilize host-protection mechanisms and egress filtering to avoid
exposing their systems to undue risk or exposing internal or NAT-ed
devices.
Although it may be easy for an operator to silently discard the
packet, it would be inappropriate for a network operator to
unilaterally discard data, in the absence of policy. RFC 1087 [10]
classifies an action that destroys the integrity of computer-based
information as unethical and unacceptable; and the Code of Ethics of
SAGE, USENIX, and LOPSA recognize the important of maintaining
integrity, reliability, and availability.
7. Datagram Transmission
7.1. Chemical Approach to the Atmospheric Link Layer
Information is sent by transmitters producing a specialized form of
smoke, most often by emitting a specialized oil onto the exhaust
manifold. The oil, held in a pressurized container, is vaporized in
a thick white smoke, producing readable display. The makeup of the
smoke is often subject to patents, and any organization interested
should consult with their attorneys. Further details on transmission
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on the Physical Layer is beyond the scope of this RFC, but
implementers MAY refer to references for help. It is by design that
the broadcast mechanism does not result in incompatibilities if
implementers choose different Physical Layer implementations.
7.2. Location
The datagram MUST be displayed in the atmosphere, at an altitude of
7000 to 17000 feet (2133 to 5181 meters). It SHOULD be written using
a "skytyping" method, similar to dot-matrix printing (Figure 4).
This method will provide better persistence of the datagram in the
presence of air currents. Additionally, it provides the ability for
parallelism by using additional avionic instruments.
####### ####### ####### #######
# # # #
# # # #
# #### # ####
# # # #
# # # #
####### ####### # #
Figure 4: Skytyping Method in the Sky
The most efficient method for broadcasting a datagram on this link
layer is the hire of specialized companies that perform this service
on a regular basis. For a large organization interested in using
this method frequently, it may be more cost-effective to develop
one's own methods.
7.3. Physical Layer Conditions
Transmission ability varies by atmospheric and regional conditions.
Adverse conditions, such as an accumulation of moisture or ice
crystals in the Physical Layer, may preclude transmission for a
period of time. During these periods, it is suggested broadcasts be
delayed, as higher-than-expected error rates may occur, and receivers
may not be prepared to process the transmission immediately.
Additionally, solar radiation conditions affect transmission in a
predictable, cyclic manner. Depending on latitude, the medium may be
unusable for a lengthy period, during which alternate arrangements
must be made.
Conditions may worsen before, during, or after a transmission,
resulting in higher-than-expected transmission error rates. Regional
operators should be familiar with their operating conditions and
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consider the feasibility of implementing a casual or robust
infrastructure on this transmission medium. Some locales lend
themselves better to regular operation than others.
8. References
8.1. Normative References
[1] Mogul, J., "Broadcasting Internet Datagrams", STD 5, RFC 919,
October 1984.
8.2. Informative References
[2] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
Address Text Representation", RFC 5952, August 2010.
[3] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986,
January 2005.
[4] Cotton, M. and L. Vegoda, "Special Use IPv4 Addresses", BCP 153,
RFC 5735, January 2010.
[5] Blanchet, M., "Special-Use IPv6 Addresses", RFC 5156, April
2008.
[6] Eastlake 3rd, D. and A. Panitz, "Reserved Top Level DNS Names",
BCP 32, RFC 2606, June 1999.
[7] Hooke, A., "Interplanetary Internet", GSAW 2003,
<http://sunset.usc.edu/gsaw/gsaw2003/s3/hooke.pdf>.
[8] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
[9] Waitzman, D., "Standard for the transmission of IP datagrams on
avian carriers", RFC 1149, April 1 1990.
[10] Defense Advanced Research Projects Agency and Internet
Activities Board, "Ethics and the Internet", RFC 1087, January
1989.
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Author's Address
Thomas Ritter
PO Box 541
Hoboken, NJ 07030
USA
EMail: tom@ritter.vg
URI: http://ritter.vg
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