Subject: [MMUSIC] file transfer mechanism query

From: "Vikram Chhibber" <[email-masked]>
Date: Thu, 14 Feb 2008 18:34:54 +0530

I have a query on the \draft-ietf-mmusic-file-transfer-mech-06 draft.
If a session for file transfer is negotiated successfully, how can a
file receiver determine whether the received MSRP SEND message is part
of the file that got accepted? Matching Content-Type and file size
does not provide definite solutions. Do we have file-transfer-id in
the MSRP message?

Thanks,
~VIkram
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From: Mahesh Anjanappa <[email-masked]>
Date: Fri, 15 Feb 2008 15:06:35 +0530

The Receiver can only check after the file transfer is complete by comparing
the value of  File-Selector  'hash' received in the SDP with value computed
on the actual file received.

If the sender has not sent hash file-selector in its Offer, the receiver can
only rely upon name, size and type to determine the correctness of the file

File-transfer-id is not carried by MSRP. A common Message-Id is used in
all MSRP SEND chunks carrying 'a' Message.
Entire file is to be transferred in single Messsage.

regards
Mahesh

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From: Miguel Garcia <[email-masked]>
Date: Fri, 15 Feb 2008 13:30:50 +0200

Hi Vrkram:

I think the "session-id" in MSRP solves your problem. The session-id 
part identifies a particular session of the participant. For example, in 
the following MSRP URL, "asfd34" is the session-id

msrp://host.example.com:8493/asfd34;tcp

Such MSRP URL is encoded in he a=path line in SDP. In MSRP, this URL is 
visible in either the To-Path or From-Path. So, when you receive an MSRP 
SEND request, you look at the From-Path and To-Path headers, and 
correlate with the a=path line in SDP. This tells you whether the MSRP 
SEND message belongs to the file-transfer MSRP session or some other 
MSRP session.

/Miguel

-- 
Miguel A. Garcia           tel:+358-50-4804586
Nokia Siemens Networks     Espoo, Finland

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From: "Vikram Chhibber" <[email-masked]>
Date: Fri, 15 Feb 2008 19:46:56 +0530

Please see inline.

>  on the actual file received.
In my opinion, this is not good approach where you perform check only
after you have downloaded the complete file moreover hash is optional.

>  only rely upon name, size and type to determine the correctness of the file
How can I use name here. I do not see MSRP message carrying the name
of the file which is getting transferred.
Size is one option but can not be used if the sender uses "*" for
total size in Byte-Range header. How about the case when the sender is
transferring two files with same size? In this case, how will the
receiver know which name should be given to which file after
completion of transfer?
I see that there are indirect ways but no straight-forward way given
by the draft.

Second query that I have is there any content-disposition header value
that indicates that the particular MSRP message needs to be stored as
file? I see render, inline and attachment which do not serve my
purpose.
>  Entire file is to be transferred in single Messsage.
I understand that file-transfer-id is not carried by MSRP, but in my
opinion it should be included in the standard to avoid these
confusions.

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From: "Vikram Chhibber" <[email-masked]>
Date: Fri, 15 Feb 2008 19:54:43 +0530

Miguel thanks. I got it.