One document matched: draft-hain-ipv6-geo-addr-02.txt
Differences from draft-hain-ipv6-geo-addr-01.txt
Network Working Group
Internet-Draft T. Hain
Intended status: Standards Track Cisco
Expires: January 2011 July 2010
An IPv6 Geographic
Global Unicast Address Format
draft-hain-ipv6-geo-addr-02.txt
Status of this Memo
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This Internet-Draft will expire on April 10, 2010.
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Abstract
This document defines an IPv6 Geographic global unicast address
format for use in the Internet. The address format defined in this
document is consistent with the IPv6 Protocol [1] and the "IPv6
Addressing Architecture" [2]. It is designed to facilitate scalable
Internet routing when sites attach to multiple service providers, by
using a prefix based on a geographic reference to the site. A
natural byproduct of this address allocation mechanism is that all
addresses are fixed allowing sites to change providers at will
without requiring their network to renumber.
Conventions used in this document
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].
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Status of this Memo................................................... 1
Abstract.............................................................. 2
Conventions used in this document..................................... 2
Introduction.......................................................... 3
Overview of the IPv6 Address.......................................... 5
IPv6 Geographic Global Unicast Address Format......................... 6
Examples.............................................................. 7
Interleave process detail: .......................................... 8
Interleave examples: ................................................ 9
Airport location examples: .......................................... 9
U.S. postal examples: .............................................. 10
Locations within a 600km square - New York area (~Zone)::/12
...... 10
Locations within a 150km square - Miami area (~Region)::/16
....... 10
Locations within a 40km square - Chicago area (~Metro)::/20
....... 10
Examples of existing exchange points & potential prefixes:
........ 11
A Geographic Multicast address format:............................... 11
Subnet Identifier.................................................... 11
Technical Motivation................................................. 11
General Considerations............................................... 12
IANA Considerations.................................................. 12
RFC Editor Considerations............................................ 12
Security Considerations.............................................. 12
Appendix A:.......................................................... 13
Appendix B:.......................................................... 16
Extended resolution ................................................ 16
References........................................................... 17
Acknowledgments...................................................... 19
Author's Addresses................................................... 19
Introduction
This document defines a Geographic global unicast address format for
IPv6 address allocation. The mechanism defined here breaks down the
geographic location of the site into prefix lengths that map well
into existing routing protocols. It is not proposing that routers
know about geography, but that a prefix that routers know how to
deal with be constructed out of something readily available which
uniquely identifies a site such as the physical-media (layer-1)
demarcation point between the public Internet and the site.
There have been numerous diatribes about how addressing has to map
to topology, often noting that existing topology does not map
cleanly to geographic structure. The fundamental point being
overlooked in these cases is that the existing topology was deployed
to minimize the local costs at the time, yet those cost factors are
not static so topology evolves over time. In particular, the costs
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associated with a bloated routing system are not factored into the
historical topology.
Another assumption that is widespread is that there has to be a
single global 'default-free-zone' (DFZ). Measured differences in BGP
updates show this to be a fallacy, even when it is the assumed
operating mode for the global transit providers. Independent of the
differing views of the DFZ there are also VPN overlays in many BGP
environments, which have explicitly different aggregate sets. In any
case, while a provider aggregate (PA) addressing architecture should
result in a single global DFZ, other aggregate sets already co-exist
so adding one more will not directly impact the existing ones. As
such the format described here is not about replacing the PA
architecture, rather it is an additional tool to deal with
situations that would bloat PA beyond utility. The expectation is
that 2 smaller tables would both use fewer resources as well as be a
closer match to the desired routing policy.
Specifically, this format is targeted at situations where smaller
organizations are looking for regional multi-homing, or other
reasons for a provider independent address block. It is assumed that
due to their commercial value service providers will not try to
discourage large organizations from continuing to use the same
approaches they have to establish explicit entries in the PA DFZ.
While these historical approaches are manageable for a relatively
small number of large organizations, the ongoing concern is that
applying them to a large number of small organizations will
effectively disable the global transit routing system.
The Geographic format described here explicitly isolates a multi-
homed site's address prefix from the set of providers it is
connected to. As a concession to operational simplicity, the format
optimizes the operational issue of identifying the demarcation point
as a direct trade-off against the consumption of address space
assigned to uninhabited regions of the planet. The overall goal is
to allow efficient routing aggregation for single sites that connect
directly to multiple providers or to metropolitan scale exchanges.
Sites will have the choice to connect to either or both types of
service. The details about specific site topology will be limited to
the service providers that are making the direct connections, and
traffic will follow the shortest path from the perspective of the
current source.
The basic mechanism is an Earth surface location defined by WGS-84
[4] latitude and longitude which represents the lower left corner of
a nominal square ~6.4m on a side (equatorial). WGS-84 was selected
because low-cost hand-held devices with the necessary level of
accuracy on a global scale are readily available. For the purposes
of this document, the term square and size of the area covered are
used as an approximation to describe the concept. Therefore the
difference in longitude vs. latitude circumference (flattening)
resulting in a difference of the latitudinal sides will be ignored
in the description, but accounted for in the measurement and
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allocation process. Interleaving is used to create a 44-bit
reference value from a 2-bit section id plus the 21-bit values
corresponding to each side of the grid. The number of subnets
supported by this address format should be sufficient for a variety
of uses.
Addresses defined with the Geographic format prefix xxxx (see IANA
considerations) are portable between providers. At the same time
since they are defined by a fixed geographic location, by definition
these prefixes are NOT-PORTABLE when a network attachment point
changes geographic locations. Entities that expect reference values
to be portable across physical location moves MUST use alternatives
such as Provider-Aggregatable addresses or DNS names. Multi-site
organizations SHOULD be using an appropriate subset of the available
prefixes, aligning desired external traffic patterns with internal
prefix distribution.
While this format is based on geographic location, it does not
necessarily require renumbering devices as they move around within
the boundaries of a specific network. This is a local decision based
on the desired external traffic patterns. The only time a
renumbering event may be required is when the demarcation point to
the public Internet is being physically moved. Even then, if the
local jurisdiction remains the same (ie: the demarcation point is
simply moving between buildings occupied by the same company) the
prefix is may be left unchanged.
One proposed use of this format is for use by mobile routers that do
happen to be aware of their geographic position. Using this format
allows these routers to construct an ad-hoc network where the
prefixes naturally aggregate for prefixes far away. At the same time
it is clear to all nodes within the geographic region what their
prefix should be, which can further be leveraged to reduce the
number of unsolicited RA messages that would unnecessarily consume
battery power.
Overview of the IPv6 Address
IPv6 addresses are 128-bit identifiers for interfaces and sets of
interfaces. There are three types of addresses: Unicast, Anycast,
and Multicast. This document defines a specific type of Unicast
address prefix. In conjunction with RFC 3306 [5], these Unicast
prefixes define a specific capability for Multicast groups to target
group members in a geographic region.
In this document, fields in addresses are given specific names, for
example "subnet". When this name is used with the term "ID" (for
"identifier") after the name (e.g., "subnet ID"), it refers to the
contents of the named field. When it is used with the term "prefix"
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(e.g. "subnet prefix") it refers to all of the addressing bits to
the left of and including this field.
IPv6 unicast addresses are designed assuming that the Internet
routing system makes forwarding decisions based on a "longest prefix
match" algorithm on arbitrary bit boundaries and does not have any
knowledge of the internal structure of IPv6 addresses. The structure
in IPv6 addresses is for assignment and allocation. Due to the
relationship between physical location of routers, geography, and
human readability there may be a tendency to manage the routers so
that they make forwarding decisions on nibble boundaries, but there
is nothing in the format requiring that. Each router will need to be
configured to forward based on a prefix length appropriate for the
context of the specific local topology.
The specific type of an IPv6 address is indicated by the leading
bits in the address. The variable-length field comprising these
leading bits is called the Format Prefix (FP). This document defines
an address format for the xxxx (binary) (see IANA considerations)
Format Prefix for Geographic reference global unicast addresses. The
same address format could be used with other Format Prefixes, as
long as these Format Prefixes also identify IPv6 unicast addresses.
For example, different FPs could be used to distinguish between
resolution boundaries for three dimensional applications (see
Extended Resolution on page 16). Only the xxxx Format Prefix is
defined here.
IPv6 Geographic Global Unicast Address Format
Geographic address prefixes use a geographic reference derived from
a bit interleave of the WGS-84 based latitude and longitude of the
demarcation point of a site. The resulting 44-bit field provides a
resolution grid of approximately 6.4 meters (equatorial) on a side.
While the prefix MAY be defined and routed on any bit boundary
length, the requirement for all service providers announcing a
specific prefix to be capable of delivering traffic to all others,
will have a tendency to naturally limit the operational choices.
| 3 | 45 bits | 16 bits | 64 bits |
+---+---------------------+-----------+----------------------------+
|001|global routing prefix| subnet ID | interface ID |
+---+---------------------+-----------+----------------------------+
Creating the Geographic address prefix is accomplished by
establishing 4 major geographic sections. Three sections are in the
band between +/- 60 degrees latitude, with the fourth split between
the poles. Using section 00 as an example, the origin is established
at WGS-84 latitude and longitude 90e 60s. Locations covering 120
degrees east and north (measured to 5 places right of the decimal
ie: deg.xxxxx) are normalized to this origin, then those values are
divided by the incremental angle. For latitudes between +/- 60
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degrees the incremental angle is 0.00005722045898437500
(120/(2^21)).
The specific sequence for address formation is:
1. demarcation WGS-84 value in degrees rounded to 5 decimal places
follow steps for appropriate section
00 - 90e 60s to 209.99999e 59.99999n
01 - 210e 60s to 329.99999e 59.99999n
10 - 330e 60s to 89.99999e 59.99999n
110 - 90e 90s to 89.99999e 59.99999s
111 - 90e 60n to 89.99999e 90n
--- equatorial band
2. normalize for origin of the section
sec 0
a) for east subtract 90 from the value
b) for west subtract the value from 270
c) for north add 60 to the value
d) for south subtract the value from 60
3. divide resulting values by 0.00005722045898437500 (120/2^21)
4. convert each of the integers to 21-digit binary
5. bit interleave latitude, longitude into 42-bit result
6. prepend the 2-bit section number
7. prepend the 4-bit FP xxxx to form 48-bit prefix
--- polar sections
2. normalize for origin of the section
sec 3 - > 60 n/s
a) for east subtract 90
.1) if less than 0, add 360
b) for west subtract from 270
.1) if less than 0, add 360
c) for north subtract 60
d) for south subtract from 90
3. divide resulting values by 0.00017166137695312500 (360/2^21)
4. convert each of the integers to 21-digit binary
5. adjust latitude value for north / south section
a) for north set bit A(21)
b) for south clear bit A(21)
6. bit interleave latitude, longitude into 42-bit result
7. prepend the 2-bit section number
8. prepend the 4-bit FP xxxx to form 48-bit prefix
Examples
The examples in the tables below highlight the difficulty of
aligning technical details of bit patterns with human meaningful
text strings. One of the explicit goals of the first table is to
identify the very large scopes devoid of geo-political context,
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while recognizing the need to provide something that an operator can
relate to as the resolution becomes finer grained. In any case these
are only descriptive examples, and actual implementations would be
based on engineering requirements.
The Reference field in the prefix MUST be calculated for a site at
44-bits, but MAY be used in routing calculations on any bit boundary
appropriate for the topology. For human reference the approximate
surface area covered by each value of the grid is provided in the
table below. The size in meters is based on rounded values for the
equatorial circumference and should only be used as a conceptual
guideline.
bits degrees equatorial sq scope sites
--------------------------------------------------------------------
2 -> 120.00000 13358 km section
4 -> 60.00000 6679 km expanse
8 -> 15.00000 1669 km frame
12 -> 3.75 417 km zone
16 -> 0.9375 104 km region
20 -> 0.234375 26 km metro 16777216
24 -> 0.05859375 6.5 km city 1048576
28 -> 0.0146484375 1.6 km locality 65536
32 -> 0.003662109375 407 m neighborhood 4096
36 -> 0.00091552734375 102 m block 256
40 -> 0.0002288818359375 25 m lot 16
44 -> 0.000057220458984375 6.4 m site 1
The location addressed as x000:0000:0000::/48 covers an area in the
Indian Ocean ~ 6.4 m on a side, north and east of the point 60
degrees south - 90 degrees east. Specifically the WGS84 values
between, 60s to 59.99994s and 90e to 90.00005e.
Interleave process detail:
A bit interleave is used to allow aggregation on arbitrary
granularities. From the left after the 4-bit format prefix, bits 123
& 122 will identify the section using the table:
00 - 90e 60s through 209.99999e 59.99999n
01 - 210e 60s through 329.99999e 59.99999n
10 - 330e 60s through 89.99999e 59.99999n
110 - 90e 90s through 89.99999e 59.99999s
111 - 90e 60n through 89.99999e 90n
Example:
Mont Orohena, Tahiti 17.62000 s 149.48000 w
This location is in section 01, where the coordinates normalize to:
A - 42.38 ; O - 0.52
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dividing those values by 120/2^21 returns:
A - 740644 ; O - 9087
converting those to hex results in:
A - B4D24 ; O - 237F
with binary equivalent from which the bits are interleaved:
A - 0 1011 0100 1101 0010 0100 ; O - 0 0000 0010 0011 0111 1111
A(21)---------------------(0); O(21)---------------------(0)
A(21)O(21) A(20)O(20)A(19)O(19) A(18)O(18)... A(1)O(1)A(0)O(0)
00 1000 1010 0010 0100 1010 0111 0001 1101 0111 0101
The 6 bits of FP and section ID are prepended with the final result:
x48A:24A7:1D75::/48
Interleave examples:
Region section lat section long bit interleave
---------------------------------------------------------
W. Europe (west) 1C0000 : 000000 -> xAA0:0000:0000::
W. Europe (east) 1C0000 : 080000 -> xAE0:0000:0000::
S. Africa 070000 : 080000 -> x86A:0000:0000::
NE Africa 148000 : 0C8000 -> xA70:0000:0000::
E. Europe 1C0000 : 110000 -> xBA1:0000:0000::
C. Asia 148000 : 000000 -> x220:8000:0000::
E. Asia 190000 : 0C0000 -> x2D2:0000:0000::
Australia 070000 : 0C0000 -> x07A:0000:0000::
Alaska 020000 : 0A0000 -> xE4C:0000:0000::
NW US 1C0000 : 088000 -> x6E0:4000:0000::
Central America 148000 : 0D0000 -> x671:8000:0000::
SE US 190000 : 100000 -> x782:0000:0000::
South America 070000 : 100000 -> x52A:0000:0000::
NW Africa 100000 : 038000 -> xA05:4000:0000::
S Pole - 90.00000 s 90.00000 e xC00:0000:0000::
N Pole - 90.00000 n 90.00000 e xF5D:DDDD:DDDD::
Airport location examples:
MIA - 25.78000 n 80.28000 w x72C:E3BF:E8D9::
ATL - 33.63000 n 84.42000 w x781:BF7A:F4F9::
IAD - 38.93000 n 77.45000 w x78D:3942:C7FF::
JFK - 40.63000 n 73.77000 w x798:B327:DDB5::
ORD - 41.97000 n 87.90000 w x78A:4A57:1978::
DEN - 39.85000 n 104.70000 w x6D8:8910:3DE6::
SFO - 37.62000 n 122.37000 w x69D:11D4:0F13::
LAX - 33.93000 n 118.40000 w x6C2:14F1:25C6::
SAN - 32.73000 n 117.18000 w x6C0:DA88:62AD::
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ANC - 61.16000 n 150.00000 w xE44:46CC:6C66::
SYD - 33.97000 s 151.17000 e x128:BA55:FBDF::
NRT - 35.75000 n 140.37000 e x2D3:94D4:C195::
DEL - 28.55000 n 77.01000 e xB7A:C2E3:051F::
CAI - 30.10000 n 31.40000 e xB80:117D:E30E::
CPT - 33.95000 s 18.60000 e x878:FF19:7284::
CDG - 49.00000 n 2.53000 e xAE2:4652:4716::
LHR - 51.47000 n 0.350000 w xAB7:DEC2:89EF::
GIG - 22.80000 s 42.23000 w x5D2:EDDB:8163::
SCL - 33.38000 s 70.78000 w x53B:0682:2119::
MEX - 19.43000 n 99.07000 w x673:49B8:798E::
U.S. postal examples:
Locations within a 600km square - New York area (~Zone)::/12
Danvers, MA - 42.56940 n 70.94246 w x79B:2398:575C::
Cambridge, MA - 42.37704 n 71.12561 w x79B:20E0:BF51::
Boston, MA - 42.21300 n 71.03300 w x79B:2056:DBA2::
Providence, RI - 41.49260 n 71.24400 w x79B:0200:94EA::
Bridgeport, CT - 41.10010 n 73.12100 w x798:EA22:B031::
Upton, NY - 40.52100 n 72.53100 w x798:E4E8:4ADA::
New York, NY - 40.42510 n 74.00200 w x798:B03A:8CAB::
Newark, NJ - 40.44080 n 74.10200 w x798:A5D1:B059::
Cherry Hill, NJ - 39.93080 n 75.01754 w x78D:DD76:FA53::
Baltimore, MD - 39.17250 n 76.36400 w x78D:6E0C:5CA6::
TysonsCorner, VA - 38.55070 n 77.13500 w x78D:347E:9A88::
Reston, VA - 38.93501 n 77.35144 w x78D:3957:BF69::
Chantilly, VA - 38.88413 n 77.43544 w x78D:33E9:6FF3::
Locations within a 150km square - Miami area (~Region)::/16
Boca Raton, FL - 26.34460 n 80.21094 w x72E:4178:3A32::
DeerfiledBeachFl - 26.30956 n 80.09917 w x72E:4425:5611::
CoralSprings, FL - 26.27140 n 80.25558 w x72E:4143:2F68::
PompanoBeach, FL - 26.23153 n 80.12346 w x72C:EEAC:8FF3::
FtLauderdale, FL - 26.12156 n 80.12878 w x72C:EE2B:5E8A::
PembrokePines,FL - 26.02427 n 80.24018 w x72C:EB44:923B::
South Miami, FL - 25.70025 n 80.30141 w x72C:E39C:2B95::
Key Biscayne, FL - 25.69210 n 80.16248 w x72C:E3D7:E98D::
Homestead, FL - 25.47664 n 80.48385 w x72C:E0CB:4E24::
Locations within a 40km square - Chicago area (~Metro)::/20
Skokie, IL - 42.03617 n 87.73283 w x78A:4B66:D89B::
Schaumburg, IL - 42.05807 n 88.04819 w x78A:4A3B:0DDC::
Chicago, IL - 41.88585 n 87.61812 w x78A:4C8E:69C4::
Oak Brook, IL - 41.78910 n 87.94009 w x78A:4870:E1F7::
DownersGrove, IL - 41.80343 n 88.01375 w x78A:4837:E16A::
Orland Park, IL - 41.61938 n 87.84225 w x78A:4387:1A7B::
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Examples of existing exchange points & potential prefixes:
LINX, London - 51.50717 n 0.00117 w xAB7::/12
AMS-IX, Amsterdam - 52.3025 n 4.93533 e xAE3::/12
NYIIX, NY - 40.70350 n 74.00783 w x798::/16
STARTAP, Chicago - 41.87650 n 87.63467 w x78A::/16
LAIIX, LA - 34.04233 n 118.24383 w x6C2:171F::/20
PAIX, Palo Alto - 37.44083 n 122.15683 w x697:BEDA::/20
SIX, Seattle - 47.61321 n 122.33799 w x6B5:9E08::/20
NSPIXP6, Tokyo - 35.62500 n 139.90750 e x2D3::/16
SII, Shanghai - 31.30200 n 121.49167 e x2C0::/16
A Geographic Multicast address format:
A public service or network administrator may wish to notify all
nodes within a given geographic area without requiring those clients
to figure out all the appropriate groups to join. Using the all-
nodes group ID 0000:0001, with RFC 3306 [5}, the PI prefix provides
a means to identify the region for the target multicast.
| 8 | 4 | 4 | 8 | 8 | 64 | 32 |
+--------+----+----+--------+--------+----------------+----------+
|11111111|flgs|scop|reserved| plen | network prefix | group ID |
+--------+----+----+--------+--------+----------------+----------+
Using this mechanism a weather warning or other public alert could
be sent to participants in an area without the alerting service
needing to individually contact the subscribers PA addresses, or the
subscribers needing to know which specific groups to join (ie:
connect me to all alerts within a 100km radius). Alternatively,
specific groups could be defined for each public alert type, and the
alert radius defined here would still apply.
Subnet Identifier
(see RFC Editor considerations)
If 0001 were selected for the FP, this document would modify both
RFC 4291 & 3587 to extend the 64 bit Interface ID field size, and 16
bit Subnet ID field into the upper half of the Format Prefix 000
space.
Technical Motivation
The design choice for the size of the fields in the Geographic
address format was based on the need to separate the address
allocation from the service provider (specifically to address the
scaling problems that mechanism creates when sites connect to
multiple providers), the need to preserve the subnet structure
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defined in [6], and the resolution of readily available handheld GPS
receivers.
General Considerations
The operational considerations : of human readability in the routing
prefix lengths versus the topology realities used by the routing
system are network dependent and outside the scope of this document.
The technical considerations : the accuracy of the WGS-84 location
reading versus the margin of error for a 21-bit resolution. When
available, 5 places of significance right of decimal in lat/long
readings results in 1 meter increment, or well within rounding error
of 21 bit resolution : while between +/- 15 degrees latitude, using
only 4 places of significance results in 11.1 meter increments which
is considerably longer than the side ~ 6.4 m of the area being
identified. (At this time, readily available consumer-grade GPS
receivers are generally accurate to 3 meters, while commercial grade
receivers have augmentation for sub-1 meter accuracy.)
Alignment of the site boundary supporting SLA with the [6] format
allows sites to use a consistent subnet structure.
IANA Considerations
A 4-bit format prefix for PI address use needs to be assigned. The
format prefix 0001 is recommended to avoid breaking up any of the
unassigned 3-bit spaces.
RFC Editor Considerations
The format prefix binary value in the xxxx examples needs to be
replaced by the value assigned by IANA.
The format prefix hex value in the xhhh: examples needs to be
replaced by the value assigned by IANA.
The Subnet Identifier section, and the matching comment in the
references section should be removed if the IANA assigned prefix is
not in 0000::/3. It should be replaced with a pointer to (ARCH) for
global scope allocations.
Security Considerations
While there may be concerns about location privacy raised by this
scheme, there is nothing inherent in this address format that would
raise any more security considerations than any other global
addressing format. If location privacy were an issue it would be
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wise to avoid this mechanism in favor of location independent
mechanisms such as Provider-Aggregatable allocations.
Appendix A:
#!/usr/bin/perl
#
# This is a derivative of a script by mcr@sandelman.ca.
# http://www.sandelman.ottawa.on.ca/SSW/ietf/geo-pi/
#
# The primary modification was to adjust for the change
# to sections and origin. This version also adds an
# option for decimal degree input format.
#
# alh-ietf@tndh.net 2002/12/31
#
print "Please select format 1) dd.mm.ss or 2) dd.ddddd: ";
chop($fmt=<STDIN>);
print "Use minus (-) for south or west values. \n";
print "Please enter your lattitude: ";
chop($lat=<STDIN>);
print "Please enter your longitude: ";
chop($long=<STDIN>);
if($fmt == 1) {
($longdeg, $longmin, $longsec) = split(/ /, $long);
($latdeg, $latmin, $latsec) = split(/ /, $lat);
if($longdeg < 0) {
$longdeg = 360 + $longdeg;
}
if($latdeg < 0) {
$latdeg = -$latdeg;
$south = 1;
}
$wgs84long = $longdeg + ($longmin / 60) + ($longsec / 360);
$wgs84lat = $latdeg + ($latmin / 60) + ($latsec / 360);
if($south == 1) {
$wgs84lat = -$wgs84lat;
}
} else {
if ($long < 0) {
$wgs84long = 360 + $long;
} else {
$wgs84long = $long;
}
}
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$wgs84lat = 90 + $lat;
# Origin is now south pole @ 0 degrees
if ($wgs84lat >= 30) {
if ($wgs84lat < 150) {
$seclat = $wgs84lat - 30;
if ($wgs84long >= 90) {
if ($wgs84long < 210) {
$section = 0;
$seclong = $wgs84long - 90;
} elsif ($wgs84long < 330) {
$section = 1;
$seclong = $wgs84long - 210;
} else {
$section = 2;
$seclong = $wgs84long - 330;
}
} else {
$section = 2;
$seclong = $wgs84long + 30;
}
} else {
$section = 7;
$seclat = $wgs84lat - 150;
$seclong = $wgs84long - 90;
}
} else {
$section = 6;
$seclat = $wgs84lat;
$seclong = $wgs84long - 90;
}
if ($seclong < 0) {
$seclong = 360 + $seclong;
}
# Origin is now normalized to section
print ("Sec Lat: $seclat \n");
print ("Sec Long: $seclong \n");
if($section < 3) {
$seclong = int($seclong / 0.000057220458984375);
$seclat = int($seclat / 0.000057220458984375);
} else {
$seclong = int($seclong / 0.00017166137695312500);
$seclat = int($seclat / 0.00017166137695312500);
}
# convert to binary
@lat = &convert_to_binary($seclat);
@long = &convert_to_binary($seclong);
@secbin = &convert_to_binary($section);
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print "Raw sec:",join('', @secbin),"\n";
print "Raw lat: ",join('', @lat),"\n";
print "Raw long:",join('', @long),"\n";
# clean off excess leading 0's
foreach $i (1..11) {
shift(@lat);
shift(@long);
}
foreach $i (1..29) {
shift(@secbin);
}
# interleave bits
@geopi=();
if ($section > 3) {
foreach $i (1..3) {
$secid = shift(@secbin);
push(@geopi, $secid);
}
} else {
shift(@secbin);
foreach $i (1..2) {
$secid = shift(@secbin);
push(@geopi, $secid);
}
}
my($o,$a);
foreach $i (1..21) {
$o = shift(@long);
$a = shift(@lat);
if ($section > 3 && $i == 1) {
# skip this bit in polar sections
} else {
push(@geopi, $a);
}
push(@geopi, $o);
}
print "Digits ",join('', @geopi),"\n";
print "Lat: $lat Long: $long -> x";
foreach $i (0..10) {
@nibble = @geopi[($i*4)..($i*4+3)];
$nibble = $nibble[0]*8 + $nibble[1]*4 + $nibble[2]*2 + $nibble[3];
print sprintf("%x", $nibble);
if($i==2 || $i==6) {
print ":";
}
}
print "\n";
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exit;
sub convert_to_binary {
local($num)=@_;
local($i, @digits);
@digits=();
foreach $i (1..32) {
if($num & 1) {
unshift(@digits, 1);
} else {
unshift(@digits, 0);
}
$num = $num >> 1;
}
return @digits;
}
Appendix B:
Extended resolution
The basic mechanism provides allocation of /48's in a two
dimensional grid. At the same time there has been interest in finer
grained resolution, as well as the ability to express altitude. The
optional extended resolution provides three dimensional cube
resolution allocations. It is expected that allocations using this
extension will continue to be aggregated such that the prefix
announcement into the public routing table is no longer than a /48.
If that expectation will not be met, the extension will require a
different format prefix.
Options for encoding the bits beyond the lat-long grid as altitude
result in various depths when the goal is a cube.
44 bit lat-long grid + 16 bit altitude
44 -> 0.000057220458984375 6.4 m site
~6.4 m cube to 419 km (260 mi) depth
46 bit lat-long grid + 14 bit altitude
46 -> 0.0000286102294921875 3.2 m room
~3.2 m cube to 52 km (172,000 ft) depth
48 bit lat-long grid + 12 bit altitude
48 -> 0.0000143051147460937 1.6 m desk
~1.6 m cube to 6.5 km (21,000 ft) depth
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