[150771] in North American Network Operators' Group
Spread Spectrum IP Addressing - SOURCE Address Field ROTATED|shifted?
daemon@ATHENA.MIT.EDU (Guru NANOG)
Sat Mar 3 14:35:16 2012
Date: Sat, 3 Mar 2012 13:34:20 -0600
From: Guru NANOG <nanog.guru@gmail.com>
To: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Common Misconception
With Spread Spectrum IP Addressing the 32-bit Source Address Field is
Shifted LEFT 2-bits by the originator of the packet.
That Folds the IPv4 Legacy Address Space into 1/4th tsize table
The lost 2-bits are stored in the Right-Most 2 bits of the 32-bit
field and in other places in the IPv4 Header
The Destination can easily recover the Source Address - if the proper
algorithms are in use
Responses blindly sent back to the shifted Source Address may fall
into agile hands or not
With the advanced Spread-Spectrum techniques, additional addressing
bits are created from the noise intentionally stored in the Right-Most
2 bits
NANOG Operators buying /8s or /6s may want to look at the
Spread-Spectrum CODE in the Linux-based CPE Routers
The following table is deprecated and 1/4th the size:
http://www.iana.org/assignments/ipv4-address-space/ipv4-address-space.txt
With Spread-Spectrum collisions and mis-directions are OK and expected but other
techniques ensure the packets get to the right place.
http://NANOG.GURU
