Subject: Caller preference draft comments

From: John Hearty <[email-masked]>
Date: Fri, 19 Mar 1999 10:13 -0600 (CST)

Nice work on this draft.  A few comments:

 I think the header/parameter approach to express the type of termination
the caller wants can work well.  I agree with Jonathan that interacting
CPL scripts between the caller and callee can get extremely complex.
With a finite set of preference parameters to consider, it should be
possible to update the CPL draft to allow these to be considered in
callee CPL scripts.  That seems to be the best place to direct the
interoperability efforts, since CPL can have more flexibility to deal
with it.

 I had a suggested addition to the parameters on page 10.  It may be
worthwhile to add "numeric" to the service-tag to cover numeric only
pagers.  I also noticed at the beginning of that section cp-params
was missing the description-param option.  Looking at the entire param
list, there is alot of specific information in it.  Maybey we need
a way to make it extensible for those specifics not yet dreamed up.

 I think some clarification is needed in section 6.4 for the cancel-feature.
I assume this means AFTER the first 200 OK, i.e. after the first 200 OK,
send a CANCEL for any other 200 OKs received.

John Hearty
MCI Worldcom
Global Network Evolution
(972)729-7976

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From: Henning Schulzrinne <[email-masked]>
Date: Sat, 20 Mar 1999 12:39:25 -0500

> interoperability efforts, since CPL can have more flexibility to deal

In general, "caller proposes, callee disposes", so adding this to the
CPL makes sense. It does have the disadvantage that this is
SIP-specific. Also, expressing this in CPL may not be that easy,
particularly since the value of many such parameters is undefined for
most calls.

> pagers. 

I've added this as a 'text/numeric' type. Somebody needs to go register
this with IANA...

>  I also noticed at the beginning of that section cp-params
> was missing the description-param option. 

Added.

>  Looking at the entire param

You can always add more values or parameters as needed.

> send a CANCEL for any other 200 OKs received.

Tried to rewrite. Note that the CANCEL is sent immediately after the
first 200 shows up, preventing (usually) the arrival of any additional
200s.

-- 
Henning Schulzrinne   http://www.cs.columbia.edu/~hgs

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From: Jonathan Lennox <[email-masked]>
Date: Mon, 22 Mar 1999 16:35:28 -0500 (EST)

> interoperability efforts, since CPL can have more flexibility to deal

Yes, I'm planning on considering this for the next draft of the CPL, though
I'm not quite sure yet how the parameters would work -- as Henning points
out, there's a complicated issue about what happens if these parameters
aren't specified.

One possibility (which has the virtue of simplicity) is to have a "location
filter" which simply filters the currently chosen location set according to
the caller's preferences.  This might even, potentially, be
parameterizable -- the filter could enable or disable certain preference
types.  The syntax for this is unclear, though.

Discussion about this issue is welcome, though it should probably be
restricted to the iptel mailing list
<mailto:[email-masked]>.  This message has been Cc'd
there.

-- 
Jonathan Lennox
[email-masked]