Re: [rtcweb] draft-ietf-rtcweb-use-cases-and-requirements-05 addition around IPv6 only and dualstack

Harald Alvestrand <harald@alvestrand.no> Mon, 26 September 2011 09:55 UTC

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Date: Mon, 26 Sep 2011 11:57:42 +0200
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Cc: "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: Re: [rtcweb] draft-ietf-rtcweb-use-cases-and-requirements-05 addition around IPv6 only and dualstack
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On 09/26/11 08:34, Magnus Westerlund wrote:
> Hi,
>
> (as individual)
>
> I would suggest that some section for general requirements that aren't
> use case specific is created and at least one such requirement is added.
>
> The requirement is the need to support IPv4 only, IPv6 only and
> dual-stack deployments as required by our charter. I think this should
> be added into the use-case and requirement document for two reasons.
> First, that is located next to the other requirements, secondly because
> W3C has decided to use our document also, I think it is important that
> such a general requirement both on protocols and any address field in
> the API handling both address families are covered.
I support adding those requirements.

I think that it can also be instantiated within the specific use cases, 
such as:
- Point to point call: One endpoint on IPv4, the other endpoint on IPv6
- Multipoint call (with and without central server): One user on IPv4, 
one user on IPv6

This is a limitation of the use-case-based model; it gets messy to 
shoehorn all the "permutations" of situations into a single set of use 
cases, without the list of use cases growing impossibly long or the use 
cases' description expanding into incomprehensibility.

On balance, I think having a "considerations applicable to all 
scenarios" section saying:

- Clients can be on IPv4-only
- Clients can be on IPv6-only
- Clients can be on dual-stack
- Clients can be on wideband (10s of Mbits/sec)
- Clients can be on narrowband (10s to 100s of Kbits/sec)
- Clients can be on variable-media-quality networks (wireless)
- Clients can be on congested networks
- Clients can be on firewalled networks with no UDP allowed
- Clients can be on networks with cone NAT
- Clients can be on networks with symmetric NAT

might be a good way to go forward.

A particular query on v4/v6 interoperation: Should we make it a 
requirement that dual-stack to IPv4 always use the IPv4 native path 
rather than a gateway functionality (and the converse for IPv6), or 
should we just be silent about it?
I think it may affect some tuning of the ICE address selection 
algorithm, in particular if we encounter 6to4 addresses. There might be 
RFCs we can cite already.


> Cheers
>
> Magnus Westerlund
>
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> Multimedia Technologies, Ericsson Research EAB/TVM
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