[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
RE: draft-ietf-v6ops-3gpp-analysis-09.txt / IESG comments on IMS Scenario 1
> 3GPP Analysis has -09 received some comments from the IESG
> and I start the mailing list discussion with the comments
> considering IMS Scenario 1. There are two comments from
> Allison and Jon:
>
> =====================================
> (1)
> Commented by:Mankin, Allison
> Comment:My understanding is that this analysis is for 3GPP,
> rather than reflecting an existing
> fully-formed 3GPP analysis, so that we influence what 3GPP thinks.
>
> 3GPP desperately needs to grapple with a robust model for
> IMS systems when
> they communication with IPv4 only hosts. (They also needs a
> model for those
> systems to deal with expressing a preference for IPv6 usage
> should vendors
> provide IPv4 IMS capability).
>
> The document wisely says that the SIP WG can do a good job
> of providing this
> model, but then unwisely both describes a model and references a more
> detailed draft. Both models are not good cross-area
> products, since they
> design a SIP ALG and a NAT-PT structure for SIP's SDP.
>
> Since SIP terminates the connection endpoints at proxies, it
> can change
> the Internet protocol at those points, therefore, it would
> be possible to
> provide a reverse NAT for IPv4 addresses and route them to
> translating
> proxies at a boundary point where the IMS system had dual stack
> capability (this is just one idea). The media situation is
> harder, but
> the review of this needs to consider capabilities such as terminating
> the media at a mixer and changing the Internet protocol there (SDP
> rewriting is not OK), using only DNS names by policy, so both ends
> of the media user could use a generic transition mechanism not
> specialized into 3GPP.
I assume that the more detailed reference draft mentioned above is
draft-elmalki-sipping-3gpp-translator-00 [3gpptr].
This draft does not design a SIP ALG and NAT-PT but avoids SDP editing
since this had been pointed out by some SIP experts already. So the purpose
was exactly to address a number of the comments you bring up and continue
working on a solution in SIPPING. Regarding the 3gpp analysis draft I think
it could state the issues more clearly (esp. SDP editing consequences) but
I am afraid that if it doesn't provide any guidance on SIP IMS it won't be
as helpful to 3gpp.
/Karim