[SIPForum-discussion] Would the fax call fail if there is a mistmatch between SDP Attributes

[Maciej Wasiel]

Hi Mustafa,
I have no idea why the second re-invite is generated by the receiving gateway. Looks like you might be dealing here with a bad implementation.
Maciej Wasiel

From: mustafa aydin [mailto:mustafaydin82 at yahoo.com]
Sent: Wednesday, August 25, 2010 3:29 AM
To: Maciej Wasiel; discussion at sipforum.org
Subject: Re: [SIPForum-discussion] Would the fax call fail if there is a mistmatch between SDP Attributes

Hi Maciej,

Receiving gw is advertising udptl as per the section from the re-invite message below;

Media Description, name and address (m): image 52392 udptl t38
Media Type: image
Media Port: 52392
Media Proto: udptl
Media Format: t38

I do not know the brands of gws which are involving to the scenario. But the call is between PBX (emmiting side) and CO (receiving side).


Regards,
Mustafa Aydin
________________________________
From: Maciej Wasiel <Maciej.Wasiel at dialogic.com>
To: mustafa aydin <mustafaydin82 at yahoo.com>; "discussion at sipforum.org" <discussion at sipforum.org>
Sent: Tue, August 24, 2010 10:47:25 PM
Subject: RE: [SIPForum-discussion] Would the fax call fail if there is a mistmatch between SDP Attributes
Hi Mustafa,
Is the receiving gateway advertising tcp and udptl? Btw, do you know which gateways are used in this call?

Maciej


From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of mustafa aydin
Sent: Tuesday, August 24, 2010 8:28 AM
To: discussion at sipforum.org
Subject: [SIPForum-discussion] Would the fax call fail if there is a mistmatch between SDP Attributes

Hello Guys,

In my scenario, the receiving gateway sends a reinvite (to negotiate t38) with the following SDP attributes;

Media Attribute (a): T38FaxVersion:0
Media Attribute (a): T38FaxMaxBuffer:1100
Media Attribute (a): T38FaxMaxDatagram:612
Media Attribute (a): T38MaxBitRate:14400
Media Attribute (a): T38FaxRateManagement:transferredTCF
Media Attribute (a): T38FaxUdpEC:t38UDPRedundancy

However, the emitting  gateway responds only with the  attributes below in 200 OK;

Media Attribute (a): T38FaxRateManagement:transferredTCF
Media Attribute (a): T38MaxBitRate:14400

Then the recieving gateway sends another reinvite with removing the "T38FaxUdpEC:t38UDPRedundancy" attribute, but this time the emitting gw responds with a 200 which has "0" at it`s image port.

My questions are; whether the mismatch between these attributes is a reason for a failure ? If so, should not  the emitting gw respond back with a failure message instead of a 200 OK ?

"draft-mule-sip-t38callflows-02.txt" indicates that only T38FaxMaxBuffer  and T38FaxMaxDatagram are optional, does it mean that all other attributes must reside at the SDP ?

Best Regards,
Mustafa Aydin


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