Re: [Fwd: Re: incompatible feedback type 2 causes problems in reusing the context for profile change]

Hi all,

Sorry about repeating some of the things Ghyslain wrote in his email. I am
struggling with the delays and user-interface of gmail:). Below
follows my reply
that I only sent to Carsten (by misstake).

Cheers, Calle

On Mon, Sep 8, 2008 at 4:15 PM, Carl Knutsson <[email protected]> wrote:
> Carsten,
>
> Please read my comments inline...
>
> On Mon, Sep 8, 2008 at 3:28 PM, Carsten Bormann <[email protected]> wrote:
>>> backward compatibility issues between
>>> RFC3095 and RFC5225 profiles.
>>
>> This discussion confuses me.
>>
>> 1) *Why* would you want to switch between RFC 5225 and RFC 3095 on one
>> channel?
>
> I am not sure I would want to this switch:), or even recommend it, but to my
> knowledge there is nothing in the RFCs that prevents it and I see no reason
> to do so.
>
>>
>> 2) *How* would you do it?  I don't understand how do this with a ROHC-over-X
>> protocol like RFC 3241, but maybe you are using something different.
>
> I cannot see how RFC 3241 prevents any user from using profiles from both
> RFC 5225 and RFC 3095, but I may have missed something. A list of profiles is
> negotiated, by agreeing on a list of 16 bit profile identifiers that
> consist of both
> version and profile. Why can't profiles from both RFC3095 or RFC5225 be
> negotiated?
>
> I haven't read this RFC for a few years, so I may be wrong. I will
> read it again
> today to see if I have missed anything.
>
>>
>> (RFC 4995 section 5.1.2 clearly spells out:
>>
>>      [...] if multiple variants of the same profile are available for a
>>      ROHC channel, the PROFILES set after negotiation MUST NOT include
>>      more than one variant of the same profile. [...]
>>
>> Note that the ROHCv2 profiles have been encoded as "variants" of the ROHCv1
>> profiles.)
>
> This text is added because of the 8 bit profile field in the IR
> packet. Since we
> don't have a profile version in IR packet, it would be impossible to
> separate for
> example the v2 RTP profile from the v1 RTP profile. Still one could negotiate
> RFC3095 UDP profile and RFC5225 RTP profile. The TCP profile can negotiated
> together with both RFC3095 and RFC5225 profiles.
>
> Cheers, Calle
>