Re: [sipcore] Feature-tags in the Path header field

Christer Holmberg <> Fri, 17 September 2010 18:11 UTC

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From: Christer Holmberg <>
To: Paul Kyzivat <>
Date: Fri, 17 Sep 2010 20:07:51 +0200
Thread-Topic: [sipcore] Feature-tags in the Path header field
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Subject: Re: [sipcore] Feature-tags in the Path header field
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>> So, if the idea of carrying feature tags in Path is ok as such, I guess one option would be an RFC which defines feature-param for Path (similar to what 4508 does for Refer-To).
>> So, the extended Path ABNF may look something like:
>> Path = "Path" HCOLON path-value *( COMMA path-value )
>> path-value = name-addr *( SEMI rr-param / feature-param )
>> (Assuming feature-param fits within the syntax for rr-param)
>>> The fact that a parameter is defined for use on one header does not automatically usable with any other header. (Unless the two headers
>>> share some common definition. For instance, if the definition of rr-param was extended for Route then I believe Path would automatically
>>> pick that up as well.)
>> I agree, and that's why I sent the e-mail to the list :)
>OK. That is something that can be discussed.
>ISTM that Path is very similar to Route, and defined to work the same.
>So either you define what these things mean for Route, or else you have
>to break the linkage and explain why these are appropriate for Path and
>not Route. Also, if they are appropriate for Path, then perhaps
>Service-Route too.

I am not sure about Route, because the value is normally either pre-defined/configured or built based on Record-Route, Path or Serivce-Route. But, I guess we would need to decide whether we allow it also for Record-Route and Service-Route. There is currently no need for it (at least not what I know about), but it would probably be wise to cover all headers if we decide to do something.