Subject: [sipcore] How does a GRUU generator know that the GRUU is globally routable?

From: Brett Tate <[email-masked]>
Date: Mon, 2 Mar 2015 09:29:09 -0500

Hi,

How does a GRUU generator know that the GRUU is globally routable by every
device which can receive it?

Thanks,
Brett

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From: Adam Roach <[email-masked]>
Date: Mon, 02 Mar 2015 09:02:55 -0600

> device which can receive it?

This is functionally the same question as asking "how do we know that an
AOR can route to the associated user's registered device(s)?"

Fundamentally, both of them are a matter of proper administrative
configuration that ensures that the domain portion of a GRUU (or AOR)
resolves to the IP address of a responsible node when RFC 3263
procedures are applied to it.

>From that point, all that's required is properly functioning logic in
that node to resolve an AOR to a user's device(s), or a GRUU to a
specific device. They're fundamentally the same operation, except that
AORs can correspond to multiple devices, while GRUUs cannot.

But I suspect you know all this.

There are lots of complaints to be leveled at the behavior of network
intermediaries that change things in ways that are incongruent with
behavior described in RFCs. I'm not entirely certain which one you're
trying to highlight here, so you'll have to be clearer. Describe a
scenario in which properly configured network elements can hand out a
GRUU which then does not route to the corresponding device, and we can
talk about what went wrong and how one might go about addressing the
situation.

/a

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From: Brett Tate <[email-masked]>
Date: Mon, 2 Mar 2015 12:43:38 -0500

> Describe a scenario in which properly configured network
> elements can hand out a GRUU which then does not route
> to the corresponding device, and we can talk about what
> went wrong and how one might go about addressing the
> situation.

I'm concerned about the issues raised within
draft-kaplan-dispatch-gruu-problematic-00.

For instance, section "5. Problems with Global Reachability" highlights
issues concerning Access-Restricted Domains, Routing-Restricted Domains, and
IPv6 Reachability.

Thanks,
Brett

---

From: Adam Roach <[email-masked]>
Date: Mon, 02 Mar 2015 12:42:10 -0600

On 3/2/15 11:43, Brett Tate wrote:
> draft-kaplan-dispatch-gruu-problematic-00. For instance, section "5.
> Problems with Global Reachability" highlights issues concerning
> Access-Restricted Domains,

Which the document freely acknowledges only arises due to a
misconfiguration (one which I find highly questionable, by the way -- if
the network were broken in the way described, then AORs couldn't route
either).

> Routing-Restricted Domains,

Which is again described as an issue of configuration, and again
questionable: the implementations I've seen use the same domain for
GRUUs as they do for AORs. If you can't route to the GRUU, then you
can't set up the call in the first place.

> and IPv6 Reachability.

The problem in that section also applies to AORs (and pretty much all
other SIP URIs, for that matter); and any solution that can be applied
to fix the AOR problem fixes the GRUU problem.

You need to keep in mind that this document is basically an apologia for
one specific behavior that Hadriel wanted to have a fig leaf of cover to
continue to do; to wit: "B2BUAs should continue to replace Contact URIs,
regardless of them being a GRUU or not." The logic in here is difficult
to follow; and, when you do untangle it, largely nonsense.

If you can offer real world examples that aren't of the form "I saw a
misconfigured network fail to work," I'd be happy to engage. This
document contains none. Any plausible example would need to explain why
"sip:[email-masked]" could route to my phone, but
"sip:[email-masked];gr" could not.

/a