Re: [Softwires] ietf-softwire: IPv4 + PSID primary key for lw4over6 binding

Andy Wingo <wingo@igalia.com> Tue, 12 July 2016 12:48 UTC

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From: Andy Wingo <wingo@igalia.com>
To: <mohamed.boucadair@orange.com>
References: <877fcrcfl4.fsf@igalia.com> <787AE7BB302AE849A7480A190F8B933008DE5EB3@OPEXCLILMA3.corporate.adroot.infra.ftgroup>
Date: Tue, 12 Jul 2016 14:48:49 +0200
In-Reply-To: <787AE7BB302AE849A7480A190F8B933008DE5EB3@OPEXCLILMA3.corporate.adroot.infra.ftgroup> (mohamed boucadair's message of "Tue, 12 Jul 2016 11:46:16 +0000")
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Subject: Re: [Softwires] ietf-softwire: IPv4 + PSID primary key for lw4over6 binding
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Hi Mohamed,

Thank you for your response.

On Tue 12 Jul 2016 13:46, <mohamed.boucadair@orange.com> writes:

> [Med] Actually, the data model allows to map a B4 to one or multiple
> softwires.
>
> The rationale for using binding-ipv6info as an index is to ease
> enforcing per-subscriber policies (e.g., limit the number of softwires
> per B4).

I am new to YANG; apologies in advance for making all of the beginner
mistakes.  My understanding of the specification

              list binding-entry {
                key "binding-ipv6info";
                description "binding entry";
                uses binding-entry;
              }

was that "binding-ipv6info" uniquely identifies the B4 (because it's a
key within the binding-entry list).  Is that not the case?  If it is the
case, how is it possible for one B4 to have multiple softwires?

>> It seems to me that one CPE could very well have multiple slices of
>> IPv4 addresses.
>
> [Med] That's possible with the current data model: distinct binding
> entries that belong to the same B4 may have distinct IPv4
> addresses. Whether the same or distinct IPv4 addresses are bound to the
> same B4 is deployment-specific. IMHO, this should be considered with
> caution as it may lead to some applications failures e.g., RTP using
> IPv4@1 while companion RTCP flows are bound to another IPv4@2.

Indeed.  Happily for me though this complexity is on the B4 side of
things ;-)  By the time it gets to the AFTR I don't have any sort of
policy decisions to make there.  It is a very pleasant standard in that
regard :)

Regards,

Andy