What ACM is all about [was: RE: MSRP-ACM compatibility]

Hi,

>>>In particular, I am skeptical about doing non-trivial changes
>>>to make MSRP work better across proprietary intermediaries without
>>>some better description of what will and will not work in 
>>>the general case (i.e. not just what will work with one vendor.)
>>
>>As said before, I don't think this is about "one vendor".
> 
>So what _is_ it about? To my knowledge, We've had only one vendor  
>stand up and say "this stuff will work across our SBCs".
> 
>You are trying to work around the behavior of proprietary middle  
>boxes. They may behave similarly in some ways, but not others. For  
>example, if other vendors don't have support for TCP media, then  
>there's not much value in this for them. Without some standard  
>behavior, or some survey of behavior like BEHAVE did with 
>NATs, we're just sort of hoping things will work most of the time. That
may be  
>good enough to write product requirements around, but it's probably  
>not good enough to write standards around.

What it is about is to allow these middle boxes to treat MSRP more or
less like any other type of TCP media, without having to modify the MSRP
messages etc.

Of course, some intermediates may not support TCP in the first place,
but that's normal. We don't expect everyone to support everything we do.

But, OMA PoC uses MSRP, so compliant intermediates will have to support
TCP. 3GPP IMS uses MSRP, so compliant intermediates will have to support
TCP. Intermediates also DO exist in other SIP networks, so in order for
MSRP to work they will have to support TCP. That is what I meant by the
statement that it's not only about one vendor.

So, in my opinion, intermediates can be expected to support TCP. The
issue is with supporting legacy MSRP, and that is what ACM is trying to
solve.

I do agree that these intermediates aren't standardized, but when it
comes to sending the media through them they all behave in the same way:
by modifying the SDP.

Of course, If we also for ACM would still use the a=path attribute for
routing, rather than the c/,- line, the intermeidates will of course
have to be able to modify the a=path attribute. But, no matter whather
that can be done using configuration (I guess that is what Hadirel
indicated for his product) or whether it requires a software patch, it's
a relatively small thing compared to having to modify MSRP messages.

Regards,

Christer