Re: [MMUSIC] SDPCapNeg Issue #1: To Add, Delete and Replace Attributes

[Flemming Andreasen <[e-mail]>]

Matt Lepinski wrote:
> Flemming,
>
> Thanks for producing a draft that captures the motivation for deletion 
> of attributes in capability negotiation.
>
> I also think that Option (B) is a good comprise that solves the 
> problem without the perception of unnecessary complexity which seems 
> to burden Option (A).
>
> The only downside of Option (B) seems to be that, unlike in Option 
> (C), if deletion is used then one needs an a=acap line for attribute 
> for every attribute, even those present in all potential configurations.
Right.
>
> For example:
>
> v=0
> o=alice 2890844526 2890842807 IN IP4 10.0.0.1
> s=Example SDP
> t=0 0
> c=IN IP4 10.0.0.1
> m=audio 51000 RTP/SAVP 0 99
> a=crypto:1 AES_CM_128_HMAC_SHA1_32...
> a=ptime:30
> a=rtpmap:99 L16/8000
> a=tcap:1 RTP/AVP
> a=acap:1 a=ptime:30
> a=acap:2 a=rtpmap:99 L16/8000
> a=pcfg:1 t=1 a=-m:1,2
>
> The above is an offer indicating a preference for RTP, and a 
> willingness to accept an S-RTP audio stream. Since we need to delete 
> the crypto attribute from the potential RTP configuration (and since 
> in Option B we have only clean-slate delete-all-attributes available) 
> we need to add a=acap lines for the a=ptime and a=rtpmap attributes.
>
> Adding these additional lines is a bit inefficient, but it doesn't 
> seem like a serious problem to me. However, if someone has a use-case 
> where deletion is required and yet the inefficiency of option (B) is 
> unacceptable, then I'd be willing to support Option (C).
OK - thanks

-- Flemming
>
> - Matt Lepinski :->
>
> Flemming Andreasen wrote:
>
>> Probably the biggest open issue we have in the SDP Capability 
>> Negotiation Framework at this point is the ability to replace and 
>> delete attributes from an actual configuration SDP when generating a 
>> potential configuration. At the Prague IETF, people asked for some 
>> more motiviation and use cases for this feature before deciding 
>> whether we should include it in the core capability negotiation 
>> framework or not. I have written a short I-D in the subject, which 
>> you can find at:
>>
>>    
>> http://www.ietf.org/internet-drafts/draft-andreasen-mmusic-sdpcapneg-att-del-00.txt 
>>
>>
>> Please take a look at this and let me know how you think we should 
>> resolve this issue. Options include:
>>
>> A) Remove the ability to delete and replace attributes completely.
>> B) Remove the ability to delete and replace individual attributes, 
>> but allow for complete removal of all attributes (clean slate)
>> C) Keep the current ability to delete and remove individual and all 
>> attributes.
>>
>> My personal preference is for option A, however in the interest of 
>> moving forward and making a reasonable compromise between 
>> functionality and complexity, my recommendation is option B.
>>
>> Thanks
>>
>> -- Flemming
>>
>>
>>
>>
>>
>>
>>
>>
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>

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