Re: [MMUSIC] Connection Data Capability (ccap) and IP-addresses (draft-ietf-mmusic-sdp-miscellaneous-caps-04)

Flemming Andreasen <fandreas@cisco.com> Wed, 10 April 2013 19:30 UTC

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Date: Wed, 10 Apr 2013 15:30:10 -0400
From: Flemming Andreasen <fandreas@cisco.com>
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Cc: jonathan@vidyo.com, mmusic@ietf.org, christer.holmberg@ericsson.com
Subject: Re: [MMUSIC] Connection Data Capability (ccap) and IP-addresses (draft-ietf-mmusic-sdp-miscellaneous-caps-04)
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On 4/8/13 2:35 AM, Simo.Veikkolainen@nokia.com wrote:
> Recapping the discussion so far:
>
>
> - ICE is the way to negotiate between different IP addresses. There seems to be no disagreement here.
>
> - since no alternative port number can be expressed, in practice the IN address needs to go to the actual configuration (address in the c= line and port number in the m= line), and the alternative PSTN address in the potential configurations. Also here, there seems to be no disagreement.
>
> - then, whether the "ccap" attribute should be limited to carry only PSTN addresses, or also other types. I'm with Flemming on this one; SDP capneg framework is already fragmented enough, and limiting the connection address capability to PSTN addresses only would again be targeted for a single use case only, whereas we should strive for general solutions.
Agree with you.

Any other comments from anybody ?

If we do not hear otherwise from anybody by the end of this week, we 
will proceed according to the above.

Thanks

-- Flemming (MMUSIC co-chair)


> Simo
>
>
> -----Original Message-----
> From: mmusic-bounces@ietf.org [mailto:mmusic-bounces@ietf.org] On Behalf Of ext Flemming Andreasen
> Sent: 25. maaliskuuta 2013 3:32
> To: Andrew Allen
> Cc: jonathan@vidyo.com; mmusic@ietf.org; christer.holmberg@ericsson.com
> Subject: Re: [MMUSIC] Connection Data Capability (ccap) and IP-addresses (draft-ietf-mmusic-sdp-miscellaneous-caps-04)
>
>
> On 3/24/13 1:33 PM, Andrew Allen wrote:
>> There is also nothing that prevents people from defining their own proprietary attributes to do such a thing but that is not part of an IETF standard and is not approved usage.
> Agreed.
>
>> If we really feel the need to discourage further such usage I suppose we could add some text stating that if CCAP s received containing an IN net  type and an IN net type is present in the corresponding Connection Attribute then the CCAP attribute MUST be ignored.
> I think that gets complicated quickly for a questionable gain. I'd
> prefer the "MUST NOT" described below with an explanation as to why it's
> there; as you note, ultimately people either decide to be spec compliant
> or not.
>
> -- Flemming
>> That way compliant implementations would not perfom the discouraged behavior.
>>
>> Andrew
>>
>> ----- Original Message -----
>> From: Flemming Andreasen [mailto:fandreas@cisco.com]
>> Sent: Sunday, March 24, 2013 10:39 AM Central Standard Time
>> To: Christer Holmberg <christer.holmberg@ericsson.com>
>> Cc: Jonathan Lennox <jonathan@vidyo.com>om>; mmusic@ietf.org <mmusic@ietf.org>
>> Subject: Re: [MMUSIC] Connection Data Capability (ccap)	and	IP-addresses	(draft-ietf-mmusic-sdp-miscellaneous-caps-04)
>>
>>
>> On 3/23/13 5:24 AM, Christer Holmberg wrote:
>>> Hi,
>>>
>>> In general I agree that having multiple ways of doing the same thing is not a good thing, and I don't have any strong feelings regarding the ccap usage.
>>>
>>> But, no matter what we say, what would actually prevent people from using ccap, in the same way they are using ANAT and altc? :)
>> There's no port signaling capability with ccap, but other than that, the
>> only thing that prevents people from using this to signal alternative
>> IP-addresses is the existence of a "MUST NOT" in the spec.
>>
>> -- Flemming
>>
>>> Regards,
>>>
>>> Christer
>>>
>>>
>>> ________________________________________
>>> From: mmusic-bounces@ietf.org [mmusic-bounces@ietf.org] on behalf of Jonathan Lennox [jonathan@vidyo.com]
>>> Sent: Friday, 22 March 2013 10:00 PM
>>> To: Flemming Andreasen
>>> Cc: mmusic@ietf.org
>>> Subject: Re: [MMUSIC] Connection Data Capability (ccap) and     IP-addresses    (draft-ietf-mmusic-sdp-miscellaneous-caps-04)
>>>
>>> Currently, the deployed SIP world has three mechanisms to allow some flavor of negotiation among multiple IP addresses: ICE, altc (despite the general disapproval of the working group), and ANAT (despite its deprecation).
>>>
>>> I think that adding ccap as a fourth member of this set would be a terrible idea; and as far as I can tell, no one wants to do that.  So we need to make it clear that that it MUST NOT be used for that purpose.
>>>
>>> In the formulation below, I think I'd say that a given media description MUST NOT indicate more than one address with an IN network type, across all its configurations (actual and potential).
>>>
>>> Obviously, different media descriptions (m= line blocks) can have different addresses.
>>>
>>> In practice, given the port number issue that started this thread, I suspect this means that the SDP offer will need to put the IN address in the actual configuration (in the c= line), and the PSTN address(es) will be in the potential configurations.
>>>
>>> On Mar 22, 2013, at 2:37 PM, Flemming Andreasen wrote:
>>>
>>>> Still waiting for more comments on this, especially from the people that
>>>> were very vocal in their complaints previously: Now is the time to speak up.
>>>>
>>>> Regardless, a few comments on the below:
>>>> 1) It allows the use of "ccap" to be used to indicate one or more "IP4"
>>>> addresses in a given SDP.
>>>> 2) It allows the use of "ccap" to be used to indicate one or more "IP6"
>>>> addresses in a given SDP.
>>>>
>>>> Nit-picking a bit on the actual text, which I think is important:
>>>> The "ccap" attribute is not what is being to select between different
>>>> IP-addresses; the use of a "ccap" attribute in a potential configuration
>>>> ("pcfg") is what is being used for this. Is the restriction that we want
>>>> here:
>>>> a) A potential configuration MUST NOT reference more than one "ccap"
>>>> attribute with a network type of "IN" ?
>>>> b) All potential configurations for a particular media description MUST
>>>> NOT reference more than one "ccap" attribute with a network type of "IN" ?
>>>> c) Something else ?
>>>>
>>>> Thanks
>>>>
>>>> -- Flemming
>>>>
>>>>
>>>>
>>>> On 3/22/13 1:35 AM, Andrew Allen wrote:
>>>>> I am OK with either of these proposals
>>>>>
>>>>> -----Original Message-----
>>>>> From: mmusic-bounces@ietf.org [mailto:mmusic-bounces@ietf.org] On Behalf Of Simo.Veikkolainen@nokia.com
>>>>> Sent: Wednesday, March 20, 2013 5:57 AM
>>>>> To: fandreas@cisco.com; mmusic@ietf.org
>>>>> Subject: Re: [MMUSIC] Connection Data Capability (ccap) and IP-addresses (draft-ietf-mmusic-sdp-miscellaneous-caps-04)
>>>>>
>>>>> I went through the discussion, and my reading is that there is agreement on not allowing ccap to be used for alternative IP address negotiation.
>>>>>
>>>>> That could be made clear in the text e.g. by modifying the second sentence Flemming quoted to read:
>>>>>
>>>>> <quote>
>>>>>        The 'ccap' attribute MUST NOT be used to select
>>>>>        between different IP connection addresses (e.g. between
>>>>>        "IP4" and "IP6" address families or different IP addresses
>>>>>         within the same IP address family).
>>>>> </quote>
>>>>>
>>>>> The ccap attribute should be able to carry either an IP or PSTN address; that way either a PSTN or an IP bearer could be offered as the highest priority configuration (in the "m=" line).  However, if we want to clarify the intended use of ccap, we could modify the first sentence to read:
>>>>>
>>>>> <quote>
>>>>>       The 'ccap' capability attribute is intended for offering
>>>>>       alternative connection addresses where the <nettype>
>>>>>       is "IN" or "PSTN", i.e. selecting between an IP based
>>>>>       bearer or a circuit-switched bearer.
>>>>> </quote>
>>>>>
>>>>> Simo
>>>>>
>>>>> -----Original Message-----
>>>>> From: mmusic-bounces@ietf.org [mailto:mmusic-bounces@ietf.org] On Behalf Of ext Flemming Andreasen
>>>>> Sent: 19. maaliskuuta 2013 8:24
>>>>> To: mmusic
>>>>> Subject: [MMUSIC] Connection Data Capability (ccap) and IP-addresses (draft-ietf-mmusic-sdp-miscellaneous-caps-04)
>>>>>
>>>>> Greetings
>>>>>
>>>>> As you may have seen, there has recently been some list discussion on the "connection data capability" defined in
>>>>> draft-ietf-mmusic-sdp-miscellaneous-caps-04 (see e.g. thread in
>>>>> http://www.ietf.org/mail-archive/web/mmusic/current/msg10472.html)
>>>>>
>>>>> To recap, the connection data capability ("ccap") provides capability negotiation capabilities for what amounts to the "c=" line in regular SDP, and as such enables negotiation of network type (such as "IN") and IP-address information (v4 and v6 addresses). The Standards Track mechanism for negotiating and determining alternative IP-address information today is ICE, and hence the draft currently includes the following wording:
>>>>> <quote>
>>>>> The 'ccap' capability attribute is intended to
>>>>>        be used only when there is no other mechanism available for
>>>>>        negotiating alternative connection address information, such as when
>>>>>        the <nettype> is different among the alternative addresses (e.g.
>>>>>        "IN" and "PSTN").  The 'ccap' attribute MUST NOT be used in
>>>>>        situations where an existing mechanism (such as Interactive
>>>>>        Connectivity Establishment (ICE) [RFC5245]) can be used to select
>>>>>        between different connection addresses (e.g.  "IP4" and "IP6" or
>>>>>        different IP addresses within the same IP address family).
>>>>> </quoted>
>>>>>
>>>>> The above text has led to some confusion as to exactly when and what "ccap" can be used for. More specifically, is it/should it ever be allowed to use "ccap" to convey an IP4 or IP6 address, and if so, under what circumstances ?
>>>>>
>>>>> If you have an opinion, please let us know.
>>>>>
>>>>> A couple of points to keep in mind:
>>>>> - The current document has been WGLC'ed without comment ~6 months ago.
>>>>> - 3GPP has a dependency on the document (however I'm not sure if that dependency includes the above "IN" feature)
>>>>> - The connection data capability is defined in a general manner to be generally useful in line with the overall capability negotiation framework (as opposed to targeted at one specific use case with one specific value)
>>>>> - There are scenarios where ICE cannot be used, even if implemented (e.g. ice-mismatch).
>>>>> - RFC 6849 (media loopback) provides for NAT traversal in the absence of ICE support
>>>>>
>>>>>
>>>>> Thanks
>>>>>
>>>>> -- Flemming
>>>>>
>>>>> _______________________________________________
>>>>> mmusic mailing list
>>>>> mmusic@ietf.org
>>>>> https://www.ietf.org/mailman/listinfo/mmusic
>>>>> _______________________________________________
>>>>> mmusic mailing list
>>>>> mmusic@ietf.org
>>>>> https://www.ietf.org/mailman/listinfo/mmusic
>>>>>
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>>>>> .
>>>>>
>>>> _______________________________________________
>>>> mmusic mailing list
>>>> mmusic@ietf.org
>>>> https://www.ietf.org/mailman/listinfo/mmusic
>>>>
>>> --
>>> Jonathan Lennox
>>> jonathan@vidyo.com
>>>
>>>
>>> _______________________________________________
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>>> mmusic@ietf.org
>>> https://www.ietf.org/mailman/listinfo/mmusic
>>> .
>>>
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