Subject: [Sipping] Comments to draft-vanelburg-sipping-served-user-01.txt

From: Miguel Garcia <[email-masked]>
Date: Thu, 19 Jul 2007 13:49:49 +0300

Hi:

Some comments to draft-vanelburg-sipipng-served-user-01.txt

1) Overloading semantics of the P-Served-User header

In section 3.2, the text in 4th paragraph makes me thing that the 
P-Served-User header is sometimes used to stop processing of the initial 
Filter Criteria in the S-CSCF; and sometimes not. Can you clarify if 
this is then intention?

In principle, if the draft defines a new header to avoid overloading in 
semantics of existing headers, then I would propose to not overload the 
semantics if the new header. You may need to define a new parameter that 
indicates whether to continue processing the filter criteria. I guess 
application servers should have the logic to provide such indication.

2) Can AS modify the value of the P-Served-User header?

I assume that S-CSCFs will insert the header and the AS will just read 
it, but never modifies it. Is this correct? I would suggest to have some 
text with the intended behavior.

3) Security considerations

The second paragraph in the security considerations is a bit soft when 
it puts a burden on "operators", when they "need to ensure that the 
P-Served-User header field is always removed from requests before these 
are sent outside the trust domain."

If the intention of the header is to be visible in the S-CSCF AS 
interface, then then burden of removing the header should be imposed to 
both nodes, where applicable. Otherwise, existing border nodes, such as 
a I-CSCFs behaving as proxies, will not understand the header and 
blindly forward it.

/Miguel
-- 
Miguel A. Garcia           tel:+358-50-4804586
Nokia Siemens Networks     Espoo, Finland

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