RE: Glen's proposal for Attribute Extension

["Glen Zorn \(gwz\)" <gwz@cisco.com>]

Nelson, David <> scribbled on Friday, August 25, 2006 7:09 AM:

> Uggh!  Let me try again, to get the ASCII art aligned.  I really
> dislike the line-wrap behavior of my current e-mail client, when it
> comes to plain text messages, with ">" quoting characters inserted.  
> 
> Glen has also suggested, as have others, that a fixed tag field
> could/should be used to address issues of attribute grouping.  The
> tag does not show up in this layout.  
> 
>>     0                   1                   2                   3
>>     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
>>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>    |     Type      |  Length       |            Vendor-Id
>>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>         Vendor-Id (cont)           | Extended type |    Length2    |
>>    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>>    |    Data... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
> 
> If we were to add it, would the format look like this?

Yes, sorry for the confusion.

> 
>       0                   1                   2                   3
>       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
>      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>      |     Type      |  Length       |            Vendor-Id
>      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>          Vendor-Id (cont)           | Extended type |    Length2    |
>      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>      |      Tag      |     Data...
>      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
> 
> An additional question -- are we suggesting that this format is a
> MUST for the Extended RADIUS Attributes, as opposed to the merely
> suggested format for VSAs?  I think we should do so.  

Me, too.

> 
> I also think that maybe we want to not use the VSA attribute type
> (26) for this purpose. 

Not sure why...

> 
>> 
>>    Type
>> 
>>       26 for Vendor-Specific.
>> 
>>    Length
>> 
>>       >= 7
>> 
>>    Vendor-Id
>> 
>>       0 (for Extended Attributes)
>> 
>>    Extended Type
>> 
>>       0:       Reserved
>>       1-250:   Allocated by IANA
>>       250-255: Reserved
>> 
>>    Length2
>> 
>>       >=0
>> 
>>       Multiple subattributes MAY be encoded within a single Extended
>>       Attribute, although they do not have to be.
> 
>      Tag
> 
>         0:        Not Used (i.e. attribute is untagged)
>         1-255:    Tag value used to aggregate attributes into groups
> 
> The value of the Tag field MAY be limited to printable ASCII values,
> for ease of human entry and interpretation. 
> 
>> For Diameter compatibility, the RADIUS Extended Type attributes
>> would need to be allocated within the Diameter AVP space.

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