[SIPForum-discussion] Transferring large MIME attachments within the SIP MESSAGE request.

[samuel]

IMHO there are several possibile options:

A) Try to use tcp but you can not assure that all intermediate proxies
will use TCP. In this case, UDP fragmentation might happen and you can
not assure what the result will be.

B) Try to setup a c line in the SDP for sending large files (FTP).
There's a draft about this topic
(http://www.ietf.org/internet-drafts/draft-isomaki-sipping-file-transfer-01.txt)
which might help you. This option might shed some light on how to
setup a TCP connection with the SDP exchange to send large files. This
option has the advantage that you do not require anything from the
intermediate proxies but only UAs supporting this file transfer will b
able to communicate.

C)Another option might be to send a link in the MESSAGE body  and the
receiving UA just use GET (or whatever is appropriate) to download the
contents pointed by the attached link.

The first option is not reliable at all and the second is just a draft
that might not reach consensous. I don't now right now if the third is
standard or not (content indirection sounds to me like something
related).

Hope it helps.
Samuel.

2006/3/28, Onur Cinar <onur.cinar at gmail.com>:
>
> Hi,
>
> I am working on a SIP based client side application that will be sending and
> receiving rich instant messages (embedded pictures and audio).
>
> The generated instant messages will be MIME encapsulated, and they will be
> transported through SIP MESSAGE requests.
>
> Regarding the RFC 3438, the size of a MESSAGE request should not exceed 1300
> bytes due to MTU limitations. Based on that, transferring the embedded
> elements through SIP MESSAGE requests does not seem like an efficient way.
>
> I am trying to follow the RFCs as much as possible in order to be compatible
> with 3rd party proxies.
>
> So, rather than using a proprietary transport mechanism between clients for
> transferring those embedded elements outside SIP signaling; I wanted to ask
> for your comments on what would be the most convenient way of doing this
> with SIP only messaging/transport.
>
> I thought about sending unique IDs for each embedded element within the SIP
> MESSAGE requests, and expecting the other client to initiate a set of
> subsequent INVITE requests (with TFTP/FSP/... media types) to fetch those
> referred elements?
>
> Thanks in advance for your help,
>
> Best regards,
> -Onur
>
> ---
> A. Onur Cinar
> Senior Software Engineer
> ARGELA Technologies
> http://www.argela.com.tr
>
>
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