[Jingle] XEP-0181: Jingle DTMF

Johansson Olle E oej at edvina.net
Thu Jul 24 03:23:37 CDT 2008

24 jul 2008 kl. 02.16 skrev Robert McQueen:

> Johansson Olle E wrote:
>> I agree that in most situtations, DTMF in the media stream is to be
>> preferred, mostly because
>> of timing issues. In some cases, DTMF is handled out of band for IVR
>> situations, then maybe
>> KPML could be used in the XMPP stream. It's an XML-based definition  
>> in
>> RFC 4730.
> What IVR situations can't just process the events out of the RTP  
> stream
> in order to find out what DTMF is being sent? I don't think this is a
> compelling argument for either a) requiring clients to implement two
> DTMF methods, or b) preventing DTMF interoperation between normal  
> Jingle
> and SIP endpoints unless the gateway does extra work.

Well, I agree. SIP has way too many DTMF methods and we don't want to
fall into the same traps. Let's try to keep Jingle clean. At least  

One big question here is how much we want to implement PSTN gateway
functionality. All of that is overloading SIP at this point. That's a  
big design
decision moving forward, a decision that would help us sort out stuff  
this. Is this something needed for jingle or something that is just  
from PSTN?

>> Please also note that 4733 REQUIRES use of SRTP, where RFC 2833  
>> doesn't.
>> That's propably why most SIP devices still only claim support of  
>> 4733.
> I think 2833-compliant endpoints can still exchange telephony events
> with 4733-compliant endpoints. It'd be pretty broken if that wasn't  
> the
> case. And it doesn't REQUIRE the use of SRTP, it just says this:
>   To meet the need for protection both of confidentiality and
>   integrity, compliant implementations SHOULD implement the Secure
>   Real-time Transport Protocol (SRTP) [7].

There was a discussion about this a while ago on one of the SIP mailing
lists where they emphasized that a SHOULD in an RFC should be parsed
as a requirement, unless you had extremely good reasons not to follow
it. For implementors a SHOULD should be treated as a MUST, according
to that discussion.

Also, please note this part above your quote:

"The telephone-event payload defined in this specification is highly  
compressed. A change in value of just one bit can result in a major  
change in meaning as decoded at the receiver. Thus, message integrity  
MUST be provided for the telephone-event payload type."
So message integrity is a MUST; confidentiality with SRTP is a SHOULD.

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