Subject: [SIP] Comparison of Media Authorization drafts

From: Burcak Beser <[email-masked]>
Date: Mon, 18 Dec 2000 16:36:08 -0800

As an author of SIP Extensions for Media Authorization"  I tried to compare
the draft with the draft "Session setup with media
authorization".<?xml:namespace prefix = o ns =
"urn:schemas-microsoft-com:office:office" />

All comments/suggestions/questions are welcome.

Burcak Beser

Pacific Broadband Communications

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Draft "SIP Extensions for Media Authorization" defines the
Media-Authorization-Token as a hex blob. The draft does not force any
meaning to the hex blob; the examples in the draft give two known uses for
this field. 

As described in the draft "Session setup with media authorization", if there
are to be many fields:

* All of these fields have to be send to the Edge Router.

* The End Host (UAS) does not necessarily know what is the meaning of any of
the proposed fields.

As a result, we can say that there is no need for SIP defined
sub-encoding(s) for the Media-Authorization-Token field. The token can be
formatted and populated as PDP and PEP agrees. 

Since it is impossible to predict from today what kind of information has to
exchange will occur between PDP and PEP (for example one possible way is
that the information will contain the Credit Card number to be billed) the
best way is to threat the information as a byte blob.

The draft  "SIP Extensions for Media Authorization" does not state in any
place (as incorrectly stated in draft "Session setup with media
authorization"):

* The end-host is connected to a known point in the network.

*  Same policy server makes decisions related to both service authorization
and resource utilization.

* Session managers and policy servers know each other's existence and have a
pre-defined trust relationship.

 The draft "SIP Extensions for Media Authorization" is written such that
only the SIP protocol use is focused; the draft clearly defines how each SIP
end will behave and how the information will be passed between them using
SIP protocol. But it does not impose any other restrictions on any other
entities or protocols. It is possible to device many other methods and
elements that the creative authorization methods will take place and the
draft only covers for all these protocols the question how to deliver the
Media-Authorization information to the UAS in a generic way.

 As a summary it can be said that the draft "SIP Extensions for Media
Authorization" includes all the features that draft "Session setup with
media authorization" proposes and enables more features/modes.