Re: [Ecrit] Ivo's review of draft-ietf-ecrit-ecall-15 - ISSUE 7

Randall Gellens <rg+ietf@randy.pensive.org> Tue, 01 November 2016 15:50 UTC

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Date: Tue, 1 Nov 2016 08:49:55 -0700
To: Ivo Sedlacek <ivo.sedlacek@ericsson.com>, Paul Kyzivat <pkyzivat@alum.mit.edu>, "ecrit@ietf.org" <ecrit@ietf.org>
From: Randall Gellens <rg+ietf@randy.pensive.org>
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Subject: Re: [Ecrit] Ivo's review of draft-ietf-ecrit-ecall-15 - ISSUE 7
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Hi Ivo,

It is explained in the same section.  A few paragraphs up it says:

    An In-Vehicle System (IVS) transmits an MSD (see Section 5) by
    encoding it per Annex A of EN 15722 [msd] and attaching it to a SIP
    message as a MIME body part per [RFC7852].

    [....]

    A PSAP or IVS transmits a metadata/control object (see Section 9) by
    encoding it per the description in this document and attaching it to
    a SIP message as a MIME body part per [RFC7852].

It also makes clear that the body part is in a multipart and which 
Content-Disposition is used:

    An MSD or a metadata/control block is always enclosed in a multipart
    (normally multipart/mixed) body part (even if it would otherwise be
    the only body part in the SIP message), since as of the date of this
    document, the use of Content-ID as a SIP header field is not defined
    (while it is defined for use as a MIME header field).

    A body part containing an MSD or metadata/control object has a
    Content-Disposition header field value containing "By-Reference".

It later uses "attach" as short-hand for the process described above:

    An In-Vehicle System (IVS) initiating an NG-eCall attaches an MSD to
    the initial INVITE and optionally attaches a metadata/control object
    informing the PSAP of its capabilities.

--Randy

At 2:01 PM +0000 11/1/16, Ivo Sedlacek wrote:

>  Hello Paul,
>
>  Your interpretation of "attach X to SIP message" makes sense to me.
>
>  However, I do not see a statement "attach X to SIP message means 
> ...." in the draft.
>
>  Kind regards
>
>  Ivo
>
>  -----Original Message-----
>  From: Ecrit [mailto:ecrit-bounces@ietf.org] On Behalf Of Paul Kyzivat
>  Sent: Tuesday, November 01, 2016 1:49 PM
>  To: ecrit@ietf.org
>  Subject: Re: [Ecrit] Ivo's review of draft-ietf-ecrit-ecall-15 - ISSUE 7
>
>  On 11/1/16 3:05 AM, Ivo Sedlacek wrote:
>>  Randall,
>>
>>  so, what does "attach" mean if it does not meant 
>> Content-Disposition: attachment?
>
>
>  IMO "attach X (to a sip message) means to package X as a mime body 
> part and include it in the body of the message. That in turn means 
> either:
>  - make it the complete body of the message if there are no other
>     parts, and if it can validly be done that way;
>
>  - include it as a subordinate body part within a multipart/mixed that
>     it the outer part of the body of the message.
>
>  In any case, it may then be necessary to do something more to 
> ensure that the recipient will know what is the intent of the body 
> part. In some cases this may be simply tagging it with appropriate 
> content-type and content-disposition. In other cases it may also 
> require including some sort of reference to it via a header field 
> in the message or somewhere in one of the other body parts.
>
>  That is a "general" answer. It needs to be defined in detail for each case.
>
>  	Thanks,
>  	Paul
>
>>  Kind regards
>>
>>  Ivo
>>
>>  -----Original Message-----
>>  From: Randall Gellens [mailto:rg+ietf@randy.pensive.org]
>>  Sent: Monday, October 31, 2016 4:52 PM
>>  To: Ivo Sedlacek <ivo.sedlacek@ericsson.com>
>>  Subject: RE: [Ecrit] Ivo's review of draft-ietf-ecrit-ecall-15 - ISSUE
>>  7
>>
>>  At 7:04 AM +0000 10/31/16, Ivo Sedlacek wrote:
>>
>>>   Hello,
>>>
>>>
>>>>   >   > >>  >  ISSUE 7
>>>>   >   > >>  >
>>>>   >   > >>  >  section 6 - "The IVS then attaches an updated MSD to a SIP
>>>>   >   > >>  >     INFO request and sends it within the dialog." -
>>>>  what is meant by
>>>>   >   > >>  > "attaching MSD to SIP INFO request"?
>>>>   >   > >>
>>>>   >   > >>  I think that's made abundantly clear in the multiple earlier
>>>>   >   > >> instances in the  same section that say "as a MIME body part".
>>>>   >   > >
>>>>   >   > >  I do not really know what "attach body to SIP request"  means.
>>>>   >   > > Likely, other readers will not know it either.
>>>>   >   > >
>>>>   >   > >  A reference to a section defining how to "attach body to
>   >>> SIP request"
>>>>   >   > > would help.
>>>>   >   >
>>>>   >   > It's the same section, just a little bit before.
>>>>   >
>>>>   >  I assume you refer -19 text stating: "[RFC7852] establishes a
>>>>  general  > mechanism for attaching blocks of
>>>>   >     data to a SIP emergency call."
>>>>
>>>>   If you look seven paragraphs above the paragraph in question (same
>>>>  section),  you'll see:
>>>>
>>>>       A PSAP or IVS transmits a metadata/control object (see Section 9) by
>>>>       encoding it per the description in this document and attaching it to
>>>>       a SIP message as a MIME body part per [RFC7852].
>>>>
>>>>   Then, three paragraphs later (four paragraphs above the paragraph
>>>>  in
>>>>   question) it uses "attach" again:
>>>>
>>>>       An In-Vehicle System (IVS) initiating an NG-eCall attaches an MSD to
>>>>       the initial INVITE and optionally attaches a metadata/control object
>>>>       informing the PSAP of its capabilities.
>>>>
>>>>   The surrounding text makes it clear that these are "attached" as
>>>>  body parts  in the SIP message.
>>>
>>>   The above still talks about "attaching"/"attaches" without
>>>  explaining what it means.
>>>
>>>   It can be easily misunderstood to refer to inclusion of a body part
>>>  with Content-Disposition "attachment" in a SIP message.
>>
>>  Not so easily misunderstood, since the text repeatedly makes it 
>> very clear which Content-Disposition value to use.
>>
>>  --
>>  Randall Gellens
>>  Opinions are personal;    facts are suspect;    I speak for myself only
>>  -------------- Randomly selected tag: --------------- Perhaps the 
>> real reason why we have always been able to champion free speech 
>> in this country is that we know perfectly well that hardly anybody 
>> has got anything to say, and that no one will listen to anyone
>>  that has.       -- Editorial, Daily Mail [British Paper, date unknown]
>>
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-- 
Randall Gellens
Opinions are personal;    facts are suspect;    I speak for myself only
-------------- Randomly selected tag: ---------------
If the facts don't fit the theory, change the facts.
                                  --Albert Einstein