Re: [Sip] Sip-199-02: majors and nits from Robert

["Christer Holmberg" <christer.holmberg at ericsson.com>]

Hi Hadriel,

I don't disagree with you.

However, there are examples where we do this kind of restrictions (e.g.
you-must-not-use-header-x-in-message-y) when we write our specs, and
later use-cases come up where those restrictions cause problems. 

Backward compability is important, but forward compability is also
important :)

As far as other SDOs are concerned, at least 3GPP doesn't specify that a
UA inserts 199 in Require.

Regards,

Christer


> -----Original Message-----
> From: Hadriel Kaplan [mailto:HKaplan at acmepacket.com] 
> Sent: 24. marraskuuta 2008 7:37
> To: Dean Willis
> Cc: Christer Holmberg; SIP IETF
> Subject: RE: [Sip] Sip-199-02: majors and nits from Robert
> 
> 
> 
> > -----Original Message-----
> > From: Dean Willis [mailto:dean.willis at softarmor.com]
> > Sent: Sunday, November 23, 2008 11:17 PM
> >
> > I'm not at all sure we can justify MUST NOT here.
> 
> And that in a nutshell is why middleboxes end up doing 
> interop fixing stuff.
> 
> 
> > It's not required for
> > interop, does not cause harm to the network,
> 
> There are thousands of deployed SIP networks.  Not one of 
> them currently supports this 199 mechanism, AFAIK.  Putting 
> it in a Require will not interoperate with any of them, and 
> has a potential for causing harm to the service SIP is 
> supposed to provide: session establishment.  Obviously this 
> interoperates in the sense that the far-end will fail it, and 
> we have to be able to add option tags in Require for some new 
> things; but this 199 mechanism isn't in the same vein as 
> privacy or replaces option tags which need to be put in 
> Require sometimes to make calls work.  Honestly we should 
> have been more careful in the past about this, so we might as 
> well start now.
> 
> You may think this is a no-brainer, and that no one would be 
> so dumb as to put it in a Require, but history has already 
> proven otherwise for other option tags.  Been there, done 
> that, have the T-shirt.  It works in the closed environment 
> they deploy in at first, and then breaks when the environment 
> grows or is no longer closed.  I can already envision what 
> will happen with 199: some other SDO will decide this 199 
> thing is a good idea and makes the user experience better, so 
> it should be required in release X of their specs.
> 
> 
> > and there are presumably
> > legit use cases (such as diagnostics) for using it in a Require.
> 
> Then say MUST NOT except for diagnostic purposes.
> 
> -hadriel
> 
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