Re: FW: CDR review ROHCoIPSec

Carl Knutsson writes:
> > On the other hand I do not know if the PROFILE of the ROHC can be
> > seen from the packet. If the recipient of compressed packet can see
> > from the packet to which profile it is using, then there is no need to
> > agree on one profile, but it is better to just announce what can be
> > received. If the profile cannot be seen from the packet, then we must
> > agree on one profile only.
> 
> The profile can be seen in the packet, but not the version. You cannot
> advertising both the RFC3095 and RFC5225 versions of a profile. A
> decompressor supporting both RFC3095 and RFC5225 profiles have to pick
> one version of each profile without knowing the capabilities of the
> compressor.

So the profile which can be seen from the packet is different than
what is seen in the 16-bit profile number which will be sent inside
the IKEv2 negotiation? 

> If the RFC3095 and RFC5225 capable decompressor advertise the RFC3095
> profiles to a RFC5225-only-compressor, you will end up with a ROHC
> channel only supporting the uncompressed profile. By having a two-way
> "negotiation-approach" you will be able to advertise all profiles you
> can handle (both RFC525 and RFC3095 profile) and with response both
> peers will agree on a common set of profiles.

There are ways to support both, i.e. the profile negotiation could be
described bit differently. I assume that newer RFC5225 version of the
same profile is better than RFC3095 version, so it would be better to
use the newer version if both are supported? If so then the
negotiation could be defined so that initiator can send both RFC3095
and RFC5225 versions, and if responder supports both it MUST not send
both of them, but only one of them and that also tells the initiator
that responder will only be using that version. I.e. if responder
replies with RFC3095 version then initiator will know that responder
does not support newer version thus will always send data in RFC3095
version. If responder selects RFC5225 version then that will be used
instead.

How many different profiles there are which could be used here in
IKEv2? Is the older RFC3095 profile really even an option with IKEv2
and IPsec use?
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