Subject: [Dime] A few more RFC3588 questions...

From: "David Connelly" <[email-masked]>
Date: Thu, 23 Feb 2006 22:20:59 -0800

I have started work on a Diameter implementation and have a few
questions regarding RFC3588 if anyone can help out:

The following description of the election process from 5.6.4 is confusing:

"The comparison proceeds by considering the shorter OctetString to be
padded with zeros so that it length is the same as the length of the
longer, then performing an octet-by-octet unsigned comparison with the
first octet being most significant. Any remaining octets are assumed
to have value 0x80."

How can there be remaining octets if the shorter OctetString was
already padded with zeros? Should the shorter string be padded with
zeros or 0x80? OpenDiameter seems to pad with 0x80's, but I'm not sure
if this interpretation is correct.

Also, why is type DiameterIdentity of type OctetString rather than
UTF8String? Won't this present an interoperability issue between two
peers which don't happen to use the same encoding for AVPs of type
DiameterIdentity? Or is there another standard which addresses how
FQDN's should be encoded in Diameter messages?  I noticed that
Ethereal happens to interpret DiameterIdentity as UTF8String, but was
wondering if it was safe to make this assumption in a Diameter
implementation as well.

Thanks,
David Connelly
BEA Systems, Inc.
[email-masked]

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From: Victor Fajardo <[email-masked]>
Date: Fri, 24 Feb 2006 09:40:38 -0500

Hi David,

>if this interpretation is correct.
I generally agree. I dont have any strong opinion about this but if the 
FQDN comparison is meant to be a simple string comparison then zero 
padding should be used. In that sense I'm not even sure if padding is 
useful since if both strings are equal up to the length of the shorter 
string, then the longer string would normally be more significant.

I'm also wondering if there is any precedence regarding FQDN comparisons 
in general, i.e. when comparing host having the same domain but the 
strings lengths are not equal.

victor