RE: RADIUS Design Guidelines

["Nelson, David" <dnelson@enterasys.com>]

Barney Wolff writes...

> Let me try it again:  What's wrong with using the special value of 0
for
> extended-type to indicate that this extended attribute is a
continuation
> of the previous one?  That way, extra logic is only exercised when
needed.

OK. Let's be a little more specific here.  I think what we are
discussing is the following format:

      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 (Value)...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-

I think that we have proposed that the Extended Attribute VSA (EA-VSA),
i.e. the VSA with a Vendor-Id = IETF, may contain multiple instances of
an Extended Attribute -- maybe we should call this an Encapsulated
Extended Attribute (EEA) to distinguish it from the EA-VSA wrapper.  For
example:

      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 (Value)...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Extended type |    Length2    |      Tag      |  Data (Value)...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      Data  (cont) ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-

In this example, if *second* instance of "Extended type" were zero,
would the value (data) portion of the second EEA be a continuation of
the first EEA in this EA, or would it possibly be a continuation of as
EEA in some other EA?

I think that this can get very complicated if we allow (a) tagging for
data structuring, and (b) multiple extended attributes in a single VSA,
and (c) a continuation "marker" of whatever sort.

Could you please restate you proposal for a "zero" EEA-type as
continuation flag, given this discussion?  I'm trying to be sure that
I'm not confused.
 
> Pardon me for grumbling, but it was specifically to avoid this sort of
> debate that some of us suggested we adopt the Diameter attribute
header.

Well, yeah, but that's not where the WG consensus came down.  Folks in
the WG wanted something much simpler.  We're just trying to nail down
all the corner conditions and figure out which ones we need to address,
and which we can simply declare off limits.


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