Subject: [p2p-sip] Is there a GRUU in P2P SIP?

From: hsinnrei at adobe.com (Henry Sinnreich)
Date: Sun, 6 Aug 2006 18:55:17 -0700

I am not sure: Is there a need for a GRUU in P2P SIP?

Thanks, Henry

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From: enrico.marocco at telecomitalia.it (Enrico Marocco)
Date: Thu, 10 Aug 2006 14:06:41 +0200

> I am not sure: Is there a need for a GRUU in P2P SIP?

AFAIA, if we decide to support multiple registrations for a single AOR,
the same requirements behind the GRUU work in SIP (eg the support for
REFER and presence when the IP in the contact header is not public) are
also valid in P2PSIP.

--
Enrico
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From: lowekamp at cs.wm.edu (Bruce Lowekamp)
Date: Thu, 10 Aug 2006 09:57:41 -0400

Within a single overlay, I think to some extent we can assume that the
P2PSIP Overlay User Identifier is, by definition, global.   However,
once that has been resolved by lookup in the DHT, the P2PSIP Overlay
User Routing Record needs to be globally routable.  In our draft,
we've generally been using either a resolvable DNS name or IP address,
but certainly GRUU would be useful here, especially for an overlay
that spans multiple domains.  There's some question in my mind whether
the Overlay User Routing Record should be an AOR or multiple GRUUs.  I
suspect the answer may vary based on the purpose of the particular
overlay, but it probably will make sense for it to be a resolvable DNS
name, IP addr, or GRUU.  However, I don't think that the GRUU
long-lived property, in particular, is necessary for use within a DHT,
so it's certainly not a requirement to use them.

In terms of providing access to P2P UAs from UAs outside the DHT, I
think there are a number of ideas for how to do that.  Again, GRUU can
be just as useful here, although I think an AOR is probably going to
be the more appropriate concept most of the time.

Bruce

On 8/6/06, Henry Sinnreich <hsinnrei at adobe.com> wrote:
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>

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From: enrico.marocco at telecomitalia.it (Enrico Marocco)
Date: Thu, 10 Aug 2006 19:46:23 +0200

> be the more appropriate concept most of the time.

An AOR identifies a user on any of his user agents; a GRUU a specific 
one.  If you don't need to reach a specific user agent -- possibly 
discovered by a presence/reg event watcher as well as referred by a 
REFER request -- you don't need to have GRUUs too.  OTOH, since IP 
addresses used in Contact: headers are often useless, if you care about 
usecases described in draft-ietf-sip-gruu-10, you have no chance but 
using GRUU.

However, once defined a method for consistently mapping a GRUU to a 
specific P2PSIP Overlay User Routing Record within an overlay, the P2P 
case is not much different from the conventional one.

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From: dean.willis at softarmor.com (Dean Willis)
Date: Fri, 11 Aug 2006 13:39:29 -0500

> so it's certainly not a requirement to use them.

GRUU is a way to work around a limitation in the SIP registration model.

In classic SIP, one registers a contact, which is then used as the  
request-URI when retargeting a request in the proxy serving the AOR.

GRUU provides something that "looks like a contact", but essentially  
serves as an alias for a route-vector (contact+path+relay bindings),  
wherein the proxy serving the GRUU translates the GRUU to the correct  
route-vector.

If instead we could register a route-vector. we wouldn't need the  
additional translation layer provided by GRUU.

The current terminology draft allows for this concept.

--
Dean

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From: enrico.marocco at telecomitalia.it (Enrico Marocco)
Date: Sat, 12 Aug 2006 02:44:54 +0200

> wherein the proxy serving the GRUU translates the GRUU to the correct  

And, correct me if I'm wrong, for porting the GRUU mechanism from 
conventional SIP to P2PSIP, it is just needed to define how such 
aliasing is done.

> The current terminology draft allows for this concept.

Since P2PSIP UAs can conceptually deal with route-vectors (P2PSIP 
Overlay Routing Records), GRUU are essentially useless in communications 
between P2PSIP UAs registered in the same overlay.  However, they would 
be used in dialogs between conventional and P2P SIP UAs.

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From: lowekamp at cs.wm.edu (Bruce Lowekamp)
Date: Fri, 11 Aug 2006 21:50:03 -0400

> be used in dialogs between conventional and P2P SIP UAs.

The DHT should be able to store GRUU records, but I agree there's no
reason to require or use them for P2PSIP Overlay Peers.  However, if a
P2PSIP Overlay Client wants to be registered in the overlay and
provides a GRUU, it should be stored and all participating nodes
should be able to use it.  Like I said before, my immediate thought is
that an AOR might be the more appropriate thing to store, but it
depends on the details of the use case.  Certainly storing GRUUs
should work. As you said, they would also be useful for calls between
conventional UAs and P2PSIP UAs.

Bruce