Subject: RE: [Sipping] I-D ACTION:draft-ietf-sipping-service-examples-05.t xt

From: "Paul D.Smith" <[email-masked]>
Date: Thu, 2 Oct 2003 13:13:05 +0100

Alan,

At the recent SIPit, we observed an issue with regard to handling a
challenge to an _initial_ INVITE.  Given that your draft  will soon become
an RFC, I wanted to draw your attention to this issue.

Assuming that the mailing list agrees with my understanding of the issue,
and that both of the options that I document below are in fact valid, I
would like to ask that you slightly modify either of your "407 challege"
examples so that your draft encompasses both behaviours.

The problem is the generation of an authorized INVITE after an _initial_
INVITE has been challenged by either a 401 or a 407.  There seem to be two
options here.

_Option 1 - An initial INVITE is treated very similarly to a reINVITE_

The second, authorized, INVITE is sent with the same Call-Id, From
(including same tags) as the original INVITE and the CSeq incremented.  Both
of your examples exhibit this behaviour.

_Option 2 - The initial INVITE failed so no dialog or call was created_

The second, authorized, INVITE is sent with a new Call-Id, From with new tag
and a new randomly selected CSeq.

We have observed both behaviours in different implementations.
Implementations that behave in one way, must interoperate with
implementations that behave in the other way.  Therefore I believe it would
be helpful if your draft documented both behaviours, to raise awareness with
implementors that they need to take both behaviours into account.

Thanks,
Paul DS.

Paul D.Smith
Network Protocols Group 
Data Connection Ltd (DCL)
Tel: +44 20 8366 1177  Email: [email-masked] 
Fax: +44 20 8363 1039  Web:   http://www.dataconnection.com

-----Original Message-----
From: Alan Johnston [mailto:[email-masked]]
Sent: 02 September 2003 19:06
To: [email-masked]
Subject: Re: [Sipping] I-D
ACTION:draft-ietf-sipping-service-examples-05.txt

All,

Here are the changes to this draft:

    - Added Transfer using Instant Messaging call flow.

    - Added discussion to Single Line Extension to talk about implicit
    dialog subscriptions.

    - Added focus behavior to mixing examples.

    - Added optional 181 Call is Being Forwarded response to call
    forwarding scenarios.

    - Fixed branch IDs

    - Added early-only tag to Replaces in Call Pickup example to avoid
    race condition.

    - Added remote-target tag in Call Pickup flow NOTIFY body so that the
    Contact URI is known.

    - Added call flow showing user agent using Error-Info header field to
    retrieve an announcement.

I think the draft is essentially complete. I would propose getting 
volunteers to do a detailed review of sections of the document, perhaps at 
the same time as WGLC.

Thanks,
Alan Johnston
MCI

At 12:59 PM 9/2/2003 -0400, [email-masked] wrote:
>A New Internet-Draft is available from the on-line Internet-Drafts 
>directories.
>This draft is a work item of the Session Initiation Proposal Investigation 
>Working Group of the IETF.
>
>         Title           : Session Initiation Protocol Service Examples
>         Author(s)       : A. Johnston, R. Sparks
>         Filename        : draft-ietf-sipping-service-examples-05.txt
>         Pages           : 166
>         Date            : 2003-9-2
>
>This document gives examples of Session Initiation Protocol (SIP)
>services.  This covers most features offered in so-called IP Centrex
>offerings from local exchange carriers and PBX (Private Branch
>Exchange) features.  Most of the services shown in this document are
>implemented in the SIP User Agents, although some require the
>assistance of a SIP Proxy.  Some require some extensions to SIP
>including the REFER, SUBSCRIBE, and NOTIFY methods and the Replaces
>and Join headers. These features are not intended to be an exhaustive
>set, but rather show implementations of common features likely to be
>implemented on SIP IP telephones in a business environment.
>
>A URL for this Internet-Draft is:
>http://www.ietf.org/internet-drafts/draft-ietf-sipping-service-examples-05.
txt
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_______________________________________________
Sipping mailing list  https://www1.ietf.org/mailman/listinfo/sipping
This list is for NEW development of the application of SIP
Use [email-masked] for questions on current sip
Use [email-masked] for new developments of core SIP