Subject: RE: [Simple] MSRP: need for 202 Accepted status code?

From: "Nancy Greene (QC/EMC)" <[email-masked]>
Date: Tue, 23 Nov 2004 10:02:22 -0600

Hi, Let me try again.

Paul writes:
>Not only does the 200 already mean "accepted" or "received", but it only 
>means it for the particular chunk of the whole message that it carries.
>
I know this. I said so in my original post.

>We already have something else to indicate that the *whole* message has 
>been processed. It is a success report for the whole message.

My point is that an interworking node may want to receive the whole message
before even starting delivery to the final recipient. It needs to give some
kind of report (in REPORT) back to the sender. 

I am proposing that if that interworking node cannot rightly say it has
successfully delivered the message with a "report-status" of 200, we should
allow that node to at least indicate it has accepted the message and will
now attempt delivery. The report-status in REPORT that I propose is 202
Accepted. This would NEVER be sent as a response to an MSRP SENT.

Nancy
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From: Ben Campbell <[email-masked]>
Date: Tue, 23 Nov 2004 13:49:45 -0600

There are to models to approach this with. One treats the gateway as if 
it were a relay. In this case, it would return a 200 response upon 
receiving the message, and depending on the report mode either return a 
report indicating it had _failed_ to deliver the message, or _not_ send 
a report indicating it had succeeded.

The other model treats the gateway as an endpoint. The fact the gateway 
receives the message indicates the message was successfully delivered. 
If a downstream failure occurs, the gateway must use some other 
mechanism to report this. That mechanism is not in scope for MSRP.

I don't see how either of these mechanisms benefit from a 202 code.

The important thing is, a 200, either in a response or a REPORT, does 
_not_ indicate that the message has been seen by a human. It merely 
indicates that the message has been received by the device. It seems to 
me that the semantics you desire for 202 are identical.

I can accept that we need some mechanism to indicate the final 
disposition of a message--but I think that work belongs elsewhere.

On Nov 23, 2004, at 10:02 AM, Nancy Greene (QC/EMC) wrote:

> My point is that an interworking node may want to receive the whole 
> message before even starting delivery to the final recipient. It needs 
> to give some kind of report (in REPORT) back to the sender.
>
>  I am proposing that if that interworking node cannot rightly say it 
> has successfully delivered the message with a "report-status" of 200, 
> we should allow that node to at least indicate it has accepted the 
> message and will now attempt delivery. The report-status in REPORT 
> that I propose is 202 Accepted. This would NEVER be sent as a response 
> to an MSRP SENT.
>
> Nancy

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From: Adam Roach <[email-masked]>
Date: Fri, 26 Nov 2004 18:23:17 -0600

Nancy Greene (QC/EMC) wrote:

> ...

I think what you're not quite understanding is that the MSRP 200 status 
code -- even when carried in REPORT messages -- *already* *means* the 
same thing as the 202 response code does in SIP.

/a

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From: Cullen Jennings <[email-masked]>
Date: Fri, 26 Nov 2004 16:34:35 -0800

> same thing as the 202 response code does in SIP.

Would it be better if we used 202 in MSRP where we are currently using 200?
Seems unlikely to me but I don't understand the difference between 202 and
200 in internet lore well enough to know.

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From: Ben Campbell <[email-masked]>
Date: Fri, 26 Nov 2004 18:46:25 -0600

> 200 in internet lore well enough to know.

If we did, then 200 could go away, as it would get used.

Actually, I think the problem is that people _expect_ these error codes 
to follow some "internet lore". They sort of mirror SIP for historical 
reasons. I am tempted to make them completely different than SIP, to 
avoid this sort of misunderstanding--but I think that would cause more 
disruption at this point that just dealing with misunderstandings. If 
nothing else, anyone who had done any implementation work would come 
after us with torches and pitchforks.

We use 200 to mean success. The meaning of "success" for MSRP means the 
message got to the device, and it will now try to do something with it. 
The subtle distinction between 200 and 202 in SIP does not exist in 
MSRP.
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