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

<mohamed.boucadair@orange.com> Tue, 12 July 2016 13:29 UTC

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From: <mohamed.boucadair@orange.com>
To: Andy Wingo <wingo@igalia.com>
Thread-Topic: [Softwires] ietf-softwire: IPv4 + PSID primary key for lw4over6 binding
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Date: Tue, 12 Jul 2016 13:07:43 +0000
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Subject: Re: [Softwires] ietf-softwire: IPv4 + PSID primary key for lw4over6 binding
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Re-,

Please see inline.

Cheers,
Med

> -----Message d'origine-----
> De : Andy Wingo [mailto:wingo@igalia.com]
> Envoyé : mardi 12 juillet 2016 14:49
> À : BOUCADAIR Mohamed IMT/OLN
> Cc : softwires@ietf.org
> Objet : Re: [Softwires] ietf-softwire: IPv4 + PSID primary key for
> lw4over6 binding
> 
> 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?

[Med] "binding-ipv6info" uniquely identifies an entry, ** not ** a B4. The B4 is identified by applying, for example, a subscriber-mask (https://tools.ietf.org/html/rfc7785#section-3). That is, a filter on all "binding-ipv6info" that belong, e.g., to the same /56. 

  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 :)

[Med] Glad to hear that it is pleasant.

> 
> Regards,
> 
> Andy