[siprec] New Version Notification for draft-yan-siprec-msrp-recording-02.txt
Paul Kyzivat <pkyzivat@alum.mit.edu> Wed, 27 August 2014 20:28 UTC
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From: Paul Kyzivat <pkyzivat@alum.mit.edu>
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Subject: [siprec] New Version Notification for draft-yan-siprec-msrp-recording-02.txt
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I just submitted a revised version of the MSRP recording draft. The following is a summary of what is different in this version. (It is in the draft too.) This version addresses comments received on the -01 version, both on the mailing list and at IETF90. The following is my list of things to address: o Define a new MIME type that is used to wrap the CS MSRP messages that are being recorded. This allows the original message to be left as-is, so it is always clear what it was. While CPIM could be used for this, defining a new type will allow capturing other necessary metadata. o Need to further consider the need to track message timing. Can the timing of messages received by the SRS on the RS MSRP stream be considered a sufficient proxy for the timing of messages in the CS, or should we explicitly pass timestamps of messages as received on the CS? (The issue was raised but not decided.) o We need to clarify that there is no guarantee that messages received on the CS have been recorded. o It was agreed that there is no need to record the MSRP URIs that are used to establish the CS MSRP session. o It is important that we maintain a 1:1 consistency between MSRP MESSAGE-IDs used in recorded CS sessions and the MESSAGE-IDs used in the RS. But we should not violate MSRP by using the same MESSAGE-IDs. We came up with the idea of adding an SRC-specific prefix to the CS message ids to create unique ones for the RS. This should be done in a standard way so that the SRS can recover the original CS message ids, in order to support correlation across redundant SRCs. o Will need to work out the details of what happens when a CS MSRP session is terminated with an incomplete message. It will be necessary to send the incomplete message to the SRS, but must it appear to be incomplete within the SRS MSRP session? o There are a variety of reasons why the SRC may not want, or be able to, record individual messages in the CS session. (One example is because the message size is greater than the maximum indicated by the SRS. Another is because the mime type of the message is a type that the SRS did not indicate support for.) There should be a type of placeholder message that can be sent to the SRS to indicate a message has been dropped, why, and some key attributes about the message. The new SIPREC wrapper mime type could be designed to serve this purpose. o REPORT messages on the CS can't be sent directly on the RS. The new SIPREC wrapper mime type could also serve as a way to encapsulate those. The primary change is to introduce a new wrapper MIME type ("application/msrp-recording") that is used in RS MSRP sessions for all CS MSRP messages that are to be recorded. This is used with SEND messages whether they have a CPIM wrapper or not. It also allows non-SEND messages from the CS to be sent intact in the RS for recording. And it provides a vehicle for carrying other data as needed. Adding another layer of wrapper could substantially increase the total amount of data send on the RS session, relative to what is present on the CS. I've tried to mitigate that via the details of the design. For SEND messages, only the body of the SEND message is wrapped. And From and To headers in this wrapper can be omitted in cases where that information is redundant. I've assumed that messages other than SEND should in general be infrequent enough that extra overhead when sending them isn't worth a lot of concern. This wrapper can carry a DateTime header. This provides a mechanism to address the timestamp issues. I've left it as optional to use. I clarified the non-guarantee of recording in the architecture section. I've provided a special header in the wrapper to carry the MESSAGE-ID from SEND messages in the CS. And SEND messages will get a separate MESSAGE-ID on the RS MSRP session when sent to the SRS. This provides the SRS with enough information to solve the correlation problem when a message is incomplete in one CS MSRP session and is resumed on another. (The problem of reassembly is left to the SRS.) The wrapper format includes a mechanism for the SRC to report dropped messages to the SRS. The wrapper format also includes a mechanism for encapsulating CS REPORT messages for sending to the SRS. I realized that this level of wrapping provides an opportunity to multiplex unrelated CS MSRP sessions on a single RS MSRP session. To allow this I've provided a way to include the session-id from the metadata, that identifies the particular CS MSRP session, as a value in the wrapper of the message sent on the RS. But I also made that optional when it is redundant. This gives a choice: multiplex but make the messages bigger, or create a separate RS MSRP session for each CS MSRP session and keep the messages smaller. I've included this as a trial balloon for discussion. I'm undecided about it. The formatting of all of this could be better. But for now I just wanted to get the basic concepts down for review. Once the approach is reasonably well worked out I'll try to improve the formatting. There are many places here where I am uncertain what normative strength to apply to individual requirements. I've indicated this inline for many of those. Please comment on this. I believe this is in line with what was discussed in Toronto. I especially want to hear whether people find this an acceptable direction, as well as thoughts on the details. And anything I might have overlooked that still needs to be addressed. Thanks, Paul -------- Original Message -------- Subject: New Version Notification for draft-yan-siprec-msrp-recording-02.txt Date: Wed, 27 Aug 2014 13:19:15 -0700 From: internet-drafts@ietf.org To: Michael Yan <michael.yan@huawei.com>, "Paul H. Kyzivat" <pkyzivat@alum.mit.edu>, "Michael Yan" <michael.yan@huawei.com>, "Paul Kyzivat" <pkyzivat@alum.mit.edu> A new version of I-D, draft-yan-siprec-msrp-recording-02.txt has been successfully submitted by Paul H. Kyzivat and posted to the IETF repository. Name: draft-yan-siprec-msrp-recording Revision: 02 Title: Overview for MSRP Recording based on SIPREC Document date: 2014-08-27 Group: Individual Submission Pages: 17 URL: http://www.ietf.org/internet-drafts/draft-yan-siprec-msrp-recording-02.txt Status: https://datatracker.ietf.org/doc/draft-yan-siprec-msrp-recording/ Htmlized: http://tools.ietf.org/html/draft-yan-siprec-msrp-recording-02 Diff: http://www.ietf.org/rfcdiff?url2=draft-yan-siprec-msrp-recording-02 Abstract: SIPREC is capable of recording interactive text media that is transmitted via RTP. However that format is not commonly used for message or chat scenarios. There is also a need for recording text media carried via MSRP. One case of note is exchange of text between hearing-impaired users and emergence service bureaus. Also, recording support is needed for MSRP used in chat conferences and multimedia conferences. This document describes how to achieve MSRP channel recording within the mechanism of SIP Recording (SIPREC). Please note that it may take a couple of minutes from the time of submission until the htmlized version and diff are available at tools.ietf.org. The IETF Secretariat
- [siprec] New Version Notification for draft-yan-s… Paul Kyzivat
- Re: [siprec] New Version Notification for draft-y… Paul Kyzivat
- Re: [siprec] New Version Notification for draft-y… Paul Kyzivat
- Re: [siprec] New Version Notification for draft-y… Paul Kyzivat
- Re: [siprec] New Version Notification for draft-y… Adrian Georgescu
- Re: [siprec] New Version Notification for draft-y… Paul Kyzivat
- Re: [siprec] New Version Notification for draft-y… Paul Kyzivat
- [siprec] MSRP privacy issues Paul Kyzivat
- [siprec] Declaring desired MSRP recording status … Paul Kyzivat
- Re: [siprec] New Version Notification for draft-y… Adrian Georgescu
- Re: [siprec] MSRP privacy issues Adrian Georgescu
- Re: [siprec] Declaring desired MSRP recording sta… Adrian Georgescu
- Re: [siprec] Declaring desired MSRP recording sta… Paul Kyzivat
- Re: [siprec] Declaring desired MSRP recording sta… Adrian Georgescu
- Re: [siprec] Declaring desired MSRP recording sta… Paul Kyzivat