Question on a NAT traversal requirement

OKUBO Sakae okubo at MXZ.MESH.NE.JP
Wed Aug 23 12:01:46 EDT 2006


Dear all who kindly responded to my question,

Now I understand the required minimum versions are coming from the 
expected use of H.225.0 generic extensibility framework and H.245 
generic parameter in the NAT traversal mechanism.

----------
9.3	Requirements on Signalling and Media Streams
b)	NAT traversal mechanisms for H.323 multimedia systems shall 
support no less than ITU-T H.323v3, H.245v7, H.225.0v4, and H.235v3. 
All later versions of H.323, H.245, H.225.0 and H.235 may be 
supported.
----------

My original difficulty was in the English expression "shall support 
no less than version n." It is negative to "less than n" hence 
equivalent to "n or higher." Furthermore, I understand that version n 
is a super-set of previous version (n-1), at least in principle ..., 
in our standards, meaning that version n entity can interwork with 
any lower version entity. Then the second sentence "may support any 
later version" would be overlapping with the first sentence.

In conclusion, a NAT traversal mechanism with the following H.323 
support conforms to this requirement (not mentioning H.245, H.225.0. 
H.235 for simplicity):

a/ v3
b/ v4
c/ v5
d/ v6
e/ v3, v4         ==> equivalent to b/
f/ v3, v5         ==> equivalent to c/
g/ v3, v6         ==> equivalent to d/
h/ v3, v4, v5     ==> equivalent to c/
i/ v3, v4, v5, v6 ==> equivalent to d/
j/ v4, v5         ==> equivalent to c/
k/ v4, v6         ==> equivalent to d/
l/ v4, v5, v6     ==> equivalent to d/
m/ v5, v6         ==> equivalent to d/

I hope I am correct.

-- 
Best regards,

OKUBO Sakae
e-mail: okubo at aoni.waseda.jp
         (<== sokubo at waseda.jp, valid until 31 March 2007)
Visiting Professor
Global Information and Telecommunication Institute (GITI)
Waseda University
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