IOS family naming

[andrey.gordon at gmail.com (Andrey Gordon)]

Hi List,
Anyone recalls ever seeing the IOS naming convention document. In particular
I'm interested in differences between families and trains.

This is all I found:
http://www.cisco.com/warp/public/620/1.html#topic1

But im looking for something a bit more recent maybe? Can figure out
differences between say SG, SGA, EW and EWA.

A link to the cipher would certainly help.

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Andrey Gordon [andrey.gordon at gmail.com]