If 'istarget' is used only to identify the value that was overwritten in
the Request-URI by a contact URI, an alternative approach would be to
flag the contact URI H-I entry as 'iscontact'. Then the UAS would just
need to look for the most recent H-I entry that is not marked
'iscontact'.
John
________________________________
From: [email protected] [mailto:[email protected]] On
Behalf Of Hans Erik van Elburg
Sent: 12 March 2009 08:35
To: Mary Barnes
Cc: [email protected]
Subject: Re: [Sip] Terminology (was RE: Fwd:
I-DACTION:draft-rosenberg-sip-target-uri-delivery-01.txt
Yes, because you are using the 3261 use of target and the
4244bis introduced definition of retarget. I thought it was clear that
we need other words as those definitions don't match the target-uri
drafts use of the terms. Also they do not suffice to provide a solution
for the use cases in the target-uri draft.
The 3261 text you refer to is exactly about the case where the
home proxy overwrites the Request-URI with a new target. This target is
teh registered contact address. And hence this would be what target-uri
calls a hop or a route. This case and this is where it gets confusing is
not a "retarget" in the target-uri draft use of the term.
The target-uri draft states:
"To avoid confusion, we
refer to a SIP URI that is an address for a user or resource
as a
"target" and a SIP URI that is a hop for reaching that user
as a
"hop".
Apparently that does not suffice to avoid confusion.
As for the tagging, speaking about the solution before agreeing
on the terminology and the problem it should solve is meaningless.
/Hans Erik van Elburg
On Thu, Mar 12, 2009 at 2:33 AM, Mary Barnes
<[email protected]> wrote:
Responses below [MB].
-----Original Message-----
From: Hans Erik van Elburg
[mailto:[email protected]]
Sent: Wednesday, March 11, 2009 6:42 PM
To: Barnes, Mary (RICH2:AR00)
Cc: Shida Schubert; [email protected]
Subject: Re: Terminology (was RE: [Sip] Fwd: I-D
ACTION:draft-rosenberg-sip-target-uri-delivery-01.txt
I was talking about the concept.
The use cases only describe cases where the target-uri
(lets call that
current target from now) has been lost when an initial
request for a
dialog or standalone request arrives at the UAS.
[MB] And I think this is where the terminology confusion
starts - I
don't think of the "lost" target-uri as being the
"current" target. In
my mind, the "current" target is reflected by the last
hi-entry and the
request-uri in the incoming request at the UAS. If the
entity that sent
the request was the entity that added the last hi-entry,
then the uri in
that hi-entry is the same as the request-URI in the SIP
request that
arrives at the UAS. I refer to the "lost" uri as the one
that was
"retargeted" - that's the one the UAS wants to pull from
the hi-entries
in the incoming request. That hi-entry was not the one
that was just
added by the entity that built the request just received
by the UAS.
That hi-entry is tagged with whatever name we are going
to tag it with
BEFORE the request is forwarded (using the term forward
per section 16.6
of RFC 3261). That tag is added once the target set of
potential
candidates for the new request uri are determined in
section 16.5 of
3261 (with "target set" being a 3261 term), just before
the request is
forwarded in section 16.6 to one of those targets. A
new hi-entry
(which will be the last hi-entry in the request received
by the UAS) is
added in section 16.6 of 3261 as the request is
forwarded. At this
point in time, the lost information is in the previous
hi-entry when the
outgoing request is sent. [/MB]
What has been lost is the current target of the request:
[MB] Right - at which point in my mind, it's no longer
the current
target ;) Maybe we call it "lost". [/MB]
Current target
The current target of an initial request for a dialog
or standalone
request is the name or address to which the request is
targeted, i.e.
either the initial target inserted in the Request-URI
by the UAC that
originates the request, or when a retarget occurred,
the target
provided in that retarget operation. Reroute and
translation
operations never change the current target.
[MB] I don't think this definition fits what you want -
i.e., if there
is no retargeting, then none of the hi-entries are
tagged - i.e., you
won't have your concept of current. The way it works is
that if no
hi-entries are tagged, then you know that there was no
retargeting, thus
you know the request-uri has not been lost. [/MB]
This defintion only makes sense when the following
definitions are used:
Name:
A name is a moniker for an entity which refers to it
in a way which
reveals nothing about where it is in a network. In
SIP, tel URI
which doesn't represent the location of the entity is
a name.
Address:
An address is an identifier for an entity which
describes it by its
location on the network. In SIP, the SIP URI itself
is a form of
address because the host part of the URI, the only
mandatory part of
the URI besides the scheme itself, indicates the
location of a SIP
server that can be used to handle the request.
Route:
Finally, a route is a sequence of SIP entities
(including the UA
itself!) which are
traversed in order to forward a request to an address
or name.
Retarget (other term might be needed, as this is highly
confusing):
A Request-URI rewrite operation that changes the
target identity of
the request.
Reroute (other term might be needed):
A Request-URI rewrite operation that does not change
the current
target of the request, but determines the route/next
hop taken to
reach the target-identity.
/Hans Erik
Mary Barnes wrote:
> So, by "target-uri concept" are you referring to the
solution in the
> current target-uri draft or the application usage as
such in the
> target-uri document (which is what I was referring
to)?
>
> Yes, the problem is that SIP doesn't differentiate the
various
> mechanisms by which a request-URI may be changed,
which is what some
> of the updated text in 4244bis is trying to do and why
we need precise
> terms. I think we all agree that.
>
> I honestly don't care what we call the tag, as long as
we're clear
> about the functionality.
>
> Mary.
>
> -----Original Message-----
> From: Hans Erik van Elburg
[mailto:[email protected]]
> Sent: Wednesday, March 11, 2009 4:40 PM
> To: Barnes, Mary (RICH2:AR00)
> Cc: Shida Schubert; [email protected]
> Subject: Re: Terminology (was RE: [Sip] Fwd: I-D
> ACTION:draft-rosenberg-sip-target-uri-delivery-01.txt
>
> The target-uri concept when defined properly is
entirely application
> agnostic.
>
> When one uses History-Info or another header as a
vehicle for this
> information then it still can be considered
application agnostic as
> any application can use this information as it likes.
>
> From SIP perspective all the Request-URI rewrites
look the same, that
> is what brought us discussing this in the first place.
>
> /Hans Erik
>
> Mary Barnes wrote:
>
>> And, I think the big issue with the terminology is
that 4244bis is
>> application agnostic, so it is tagging what happens
to the URIs
>> (why/how the specific URI was overwritten). Whereas,
specific
>> applications can derive information, such as what
"is" the real
>> "target" for the request, from the History-Info
header. So, IMHO,
>> it's a matter of the target-uri document specifying
that the last
>> entry tagged by whatever name we come up with "is"
the real "target"
>> for the request. I believe it's up to the
applications to describe
>> how they make use of the History-Info and not for the
History-Info to
>> describe how applications can use it. History-Info
purely reflects
>> what happened from a SIP Protocol perspective and
should not imply
>> any
>>
>
>
>> application semantics. Indeed the intent of section 5
of 4244 was to
>> inform the applications how they should decribe their
usage of the
>> header.
>>
>> Mary.
>> Note: I changed the subject to hopefully make this
topic easier to
>> keep track of.
>>
>>
---------------------------------------------------------------------
>> -
>> --
>> *From:* Hans Erik van Elburg
[mailto:[email protected]]
>> *Sent:* Wednesday, March 11, 2009 3:59 AM
>> *To:* Shida Schubert
>> *Cc:* [email protected] List; Barnes, Mary (RICH2:AR00)
>> *Subject:* Re: [Sip] Fwd: I-D
>> ACTION:draft-rosenberg-sip-target-uri-delivery-01.txt
>>
>> One of the problems that made the discussion quite
tedious is the
>> complete inversed meaning of the terms "retarget" and
"reroute"
>> between 4244bis and target-uri factions have.
>>
>> Conclusion was that the terminology need to be
properly defined and
>> some attempt was made to start such activity.
>>
>> On 3. I have strong concerns when we start tagging
the URI as to how
>> they come about "retarget"/"mapped conficuration"
etc. It is better
>> to
>>
>
>
>> embellish them with a tag that just represents there
meaning for
>> example "istarget" or "hop". For the following
reasons:
>> 1. It is much more intuitive for the user of this
information, its
>> meaning can basically be guessed.
>> 2. Such meaning also probably survives application in
other problem
>> spaces that we had not foreseen when introducing the
concept.
>>
>> The solution that is described now in the target-URI
delivery draft
>> is not yet complete, it does not solve the freephone
use case for
>> example and in its current form it will deliver
exactly the same
>> target-URI as that which would be delivered by the
P-Called-Party-ID
>> header. Contrary to what the draft says. So some work
is needed
still.
>>
>> /Hans Erik van Elburg
>>
>>
>> On Wed, Mar 11, 2009 at 7:13 AM, Shida Schubert
<[email protected]
>> <mailto:[email protected]>> wrote:
>>
>>
>> We have submitted the updated target-uri draft
based on the
>>
> comments
>
>> submitted to the list and comments received at
IETF73.
>>
>> I have taken over as editor as Jonathan didn't
have the cycles to
>> update the draft, with Francois, Christer and
Hans Erick as
>> additional
>> co-authors and great deal of help from Mary.
>>
>> The following summarizes the changes made to the
target-uri
>>
> document
>
>> 1. Added use-case for toll-free number back
>> 2. Added definition of "retarget" operation.
>> 3. Removed a reference to URN
>> 4. Added a text discussing the difference to
P-Called-Party-Id
>> 5. Changed parameter name from "target" to
"istarget"
>>
>> Note, that the target-uri document still contains
the normative
>> text for the
>> History-Info header.
>>
>> In addition, Mary (with Francois as co-author)
has submitted a
>> rfc4244bis, with the following changes:
>> 1. Incorporated the normative aspects of the
target-uri document
>> into the existing normative text in RFC 4244 -
the functionality
>>
> is
>
>> virtually identical (as is some of the text) as
the HI based
>>
> solution
>
>> described in the target-uri document. It's
important that the
>> solution
>> be integrated into RFC 4244 as it MUST work and
be based on the
>> normative
>> aspects of RFC 4244.
>> 2. Added the use cases from target-uri the the
summary
>> in the overview of rfc4244bis.
>> 3. Added an additional requirement to capture the
"target-uri"
>> information.
>> 4. Fixed an error in the RFC 4244 ABNF and added
"retarget"
>>
> parameter.
>
>> 5. Added a more simplified example.
>>
>>
>> We had some very long offline exchanges as to the
best way
>> forward
>>
> and
>
>> remaining work for both documents.
>>
>> Some of the issues identified are:
>>
>> ::Issues::
>> 1. Should we remove the normative text from
target-uri and
>>
> progress
>
>> 4244bis along with the target-uri document
to meet the
>> chartered
>> SIP WG milestone?
>>
>>
>> 2. Name of the parameter.
>> At the last meeting, parameter "target" was
said
>>
> inappropriate
>
>> because voicemail-uri spec already defines
a parameter
>>
> called
>
>> "target" which also can be found in
hi-entry, thus
>>
> potentially
>
>> causing confusion.
>>
>> Currently the target-uri draft uses
"istarget" and 4244bis
>>
> uses
>
>> "retarget" but we could never come to
>> a consensus on what name is appropriate.
Other suggestions
>>
> have
>
>> included the following:
>> "target-identity" (someone didn't like that
"identity" is
>> also a SIP header)
>> "reg-uri" (can be paired with "mapped-uri"
for item 3
>>
> below)
>
>> "aor"
>> "jibberish"
>> etc.
>>
>> One reason this is so difficult relates to
the problem
>> statement in target-uri in that
>> RFC 3261 doesn't differentiate the
mechanism by which the
>>
> new
>
>> (target) Request-URI is selected. Another
issue is that
>> some of the terminology in
>> RFC 3261 is overloaded - e.g., "forwarding"
refers both to
a
>> Proxy
>> which does not have responsibility for the
domain of the
>> request-URI
>> in the incoming request, thus the proxy
just "forwards" the
>> request to
>> the next hop AND "forwarding" is used to
describe the
>> process whereby
>> the outgoing request is built and
"forwarded" to the next
>> hop at which
>> point the proxy does not know how the new
request-uri was
>> selected.
>> RFC 4244 has attempted to clarify the terms
and attempts to
>> use "forward"
>> in the context of the former situation and
"retarget" for
>> the case whereby
>> a proxy is responsible for the domain and
thus can use a
>> number of
>> mechanism to select the new target for the
request - e.g.,
a
>> REGISTRAR,
>> configured data, etc.
>>
>> 3. Related to the last point in item 2 above,
it has been
>> proposed that
>> we differentiate the hi-entries even more
by defining
>> separate parameters
>> for registered and configured/mapped
contacts.
>> Currently when the R-URI is translated to a
URI which is
>> either derived
>> from location service lookup(registered by
UA) or from
>>
> mapping
>
>> table, there is no differentiation as to how
the URI was
>> derived once it is
>> added to the list of potential targets.
>>
>> The general consensus of the authors of the
two documents
was
>> that it may
>> be useful for some services to have the
hi-entries tagged
>> with the
>> more specific information.
>>
>> And, of course, this gets us into another
naming contest. In
>> the end, the naming
>> is not so important as long as the term
isn't too overloaded
>> and it is defined
>> precisely in the document(s).
>>
>> We would appreciate WG feedback on these issues
and any other
>> comments on
>> the two documents prior to IETF-74.
>>
>> Regards,
>> Shida and Mary.
>>
>>
>>
>> Begin forwarded message:
>>
>>> *From: *[email protected]
>>>
> <mailto:[email protected]>
>
>>> *Date: *March 10, 2009 2:30:01 AM JST
>>> *To: *[email protected]
<mailto:[email protected]>
>>> *Subject: **I-D
>>>
ACTION:draft-rosenberg-sip-target-uri-delivery-01.txt *
>>> *Reply-To: *[email protected]
>>> <mailto:[email protected]>
>>>
>>> A New Internet-Draft is available from the
on-line
>>>
> Internet-Drafts
>
>>> directories.
>>>
>>>
>>> Title
>>> : Delivery of Request-URI Targets to User Agents
>>> Author(s)
>>> : J. Rosenberg, H. van Elburg, C. Holmberg, F.
Audet, S.
Schubert
>>> Filename :
draft-rosenberg-sip-target-uri-delivery-01.txt
>>> Pages
>>> : 16
>>> Date
>>> : 2009-3-9
>>>
>>> When a Session Initiation Protocol (SIP) proxy
receives a
request
>>> targeted at a URI identifying a user or
resource it is
>>>
> responsible
>
>>> for, the proxy translates the URI to a
registered or
configured
>>> contact URI of an agent representing that user
or resource.
>>> In
>>>
> the
>
>>> process, the original URI is removed from the
request.
>>> Numerous use
>>> cases have arisen which require this
information to be
>>>
> delivered to
>
>>> the user agent. This document describes these
use cases and
>>> defines
>>> an extension to the History-Info header field
which allows it
>>>
> to be
>
>>> used to support those cases.
>>>
>>> A URL for this Internet-Draft is:
>>>
>>>
http://www.ietf.org/internet-drafts/draft-rosenberg-sip-target-uri-d
>>> e
>>> livery-01.txt
>>>
>>> Internet-Drafts are also available by anonymous
FTP at:
>>> ftp://ftp.ietf.org/internet-drafts/
>>>
>>> Below is the data which will enable a MIME
compliant mail reader
>>> implementation to automatically retrieve the
ASCII version of
the
>>> Internet-Draft.
>>>
>> Content-Type: text/plain<BR>Content-ID:
>> <[email protected]
<mailto:lt%[email protected]>
>> <mailto:[email protected]>><BR><BR>
>>
>>> _______________________________________________
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>>>
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>>> or ftp://ftp.ietf.org/ietf/1shadow-sites.txt
>>>
>> _______________________________________________
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>> This list is for NEW development of the core SIP
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>
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