Subject: no overall type in Extended Attributes

From: "Glen Zorn" <[email-masked]>
Date: Tue, 12 Aug 2008 18:42:28 +0700

As I mentioned a couple of times at the Dublin session, the current
definition of the Extended Attributes 
(http://www.ietf.org/internet-drafts/draft-ietf-radext-extended-attributes-0
4.txt) doesn't in general allow the definition of an overall type for the
Attribute in question:  an Extended Attribute is basically just an unordered
set of TLVs.  This fact doesn't bother me much, if at all, but the second
time I mentioned it there was some grumbling from the crowd, so I thought
I'd bring it up one more time on the list...

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From: "David B. Nelson" <[email-masked]>
Date: Tue, 12 Aug 2008 08:40:18 -0400

Glen Zorn writes...

> ...the current definition of the Extended Attributes
> doesn't in general allow the definition of an overall type for the
> Attribute in question: an Extended Attribute is basically just an
> unordered set of TLVs.

In other words, the Extended Attribute is a "super attribute" or "wrapper
attribute" that contains other "attributes", which you refer to as "TLVs",
to distinguish them from standalone attributes.

The issue is that one cannot "name" any particular group of aggregated TLVs.
One solution is to simply add a Group-Name TLV to the Extended Attribute.
I'm not sure that addresses the intended use, however.  I suspect that the
use is to "call up" a pre-defined grouping by name.

I think I'd like to see some "real-world" examples of use cases discussed
here before I would want to attempt to make a decision on whether this is a
serious issue or not.

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From: "Glen Zorn" <[email-masked]>
Date: Tue, 12 Aug 2008 20:55:50 +0700

David B. Nelson <mailto://[email-masked]>  writes:

> attribute" that contains other "attributes", 

In other words, the Extended Attributes have the same qualities as RFC 2865
VSAs.

> which you refer to as
> "TLVs",

I wouldn't call it an "issue" -- whether it's an issue is what is to be
determined.  It is a characteristic.

> use is to "call up" a pre-defined grouping by name.

I don't know what use it would actually be, outside of making discussions of
the protocol a little easier.  It certainly doesn't modify the operation of
the protocol.