Subject: [Sip] SIP trapezoid (was Re: IETF solution for pairing cellular hosts)

From: "Pars Mutaf" <[email-masked]>
Date: Fri, 12 Oct 2007 15:19:00 +0200

Hello,

Is the SIP trapezoid needed in cellular networks?
This is a deployment question. The very simple logic
of my question is as follows:

For privacy reasons:
- cellular users don't publish their SIP URIs in a
  phonebook.
- unpredictable and long SIP URIs are recommended.

Thus the SIP URI will be:

       n-random-characters@domainname

which may be too long to read/type as we do
today when two cell phone users meet each other?

If so:
Any solution is welcome (e.g. pairing) to help
users exchange their SIP URIs easily. For example,
user names are locally published, I choose the name
of my friend in a wireless network, and get the SIP URI.

If such solution exists:
Why not use it also for exchanging a Mobile IPv6
home address. I.e., I get my friend's SIP URI and
home address concurrently. [bonus result: we can
establish IPsec since we already know our IP addresses].

Conclusion:
By the basic SIP privacy requirement we also came to
solving the routing problem.

What I am missing?

Thanks,
pars
_______________________________________________
Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use [email-masked] for questions on current sip
Use [email-masked] for new developments on the application of sip

---

From: Paul Kyzivat <[email-masked]>
Date: Fri, 12 Oct 2007 10:57:24 -0400

> today when two cell phone users meet each other?

We may have a different usage model in mind.

AFAIK cellular users are identified by their phone number, which is used 
for humman interchange of addresses all the time. When rendered as a 
URI, it can be a TEL URI, or a sip uri. When a sip URI it has a 
particular domain, which may not normally be known to the caller. But in 
that case they start with a TEL uri and it gets translated along the way 
- typically with ENUM. In any case it isn't the caller's concern.

The mobile *device* has a different, contact, address. But callers are 
never expected to know that. It is the point of the sip trapezoid 
(actually just part of it - the home proxy) to do this translation.

	Paul

> ------------------------------------------------------------------------
>

---

From: "Pars Mutaf" <[email-masked]>
Date: Fri, 12 Oct 2007 17:12:49 +0200

> (actually just part of it - the home proxy) to do this translation.

In my simplistic view:
I need my packets routed from my device to the other device.
Mobile IPv6 home address does that (including location
management, i.e. locating the target device when I make a call).

I'm not saying that Mobile IPv6 home address corresponds to the
telephone number. We still have a SIP URI for the SIP application.

Thanks,
pars

        Paul

---

From: Paul Kyzivat <[email-masked]>
Date: Fri, 12 Oct 2007 12:09:43 -0400

Pars Mutaf wrote:
> 
> 
> On 10/12/07, *Paul Kyzivat* <[email-masked] 
> <mailto:[email-masked]>> wrote:
> 
> 
> 
>     Pars Mutaf wrote:
>      > Hello,
>      >

Then I don't understand what problem you are trying to solve.

If you wish to communicate with me via SIP then you should be trying to 
discover my Address of Record (AoR - either a SIP or possibly a TEL 
URI). The sip infrastructure will take care of routing to the device. 
AoRs will typically be user friendly to the same extent that email 
addresses or phone numbers are.

	Paul

> Thanks,
> pars
> 
> 
>  
> 
>             Paul
> 
>      > If so:
>      > Any solution is welcome ( e.g. pairing) to help
>      > Use [email-masked]
>     <mailto:[email-masked]> for questions on current sip
>      > Use [email-masked] <mailto:[email-masked]> for new
>     developments on the application of sip
> 
>

---

From: "Pars Mutaf" <[email-masked]>
Date: Fri, 12 Oct 2007 18:51:01 +0200

On 10/12/07, Paul Kyzivat <[email-masked]> wrote:
> URI).

The privacy problem: normally I shouldn't be able to discover
your SIP URI.

Then, we turn back to my initial question in this thread:
(really sorry I couldn't make it shorter!)

http://www1.ietf.org/mail-archive/web/sip/current/msg20730.html

Thanks!
pars

The sip infrastructure will take care of routing to the device.

---

From: Spencer Dawkins <[email-masked]>
Date: Fri, 12 Oct 2007 12:13:29 -0500

your SIP URI.

I'm guessing that if you can't tell people your SIP AOR, then SIP is not for 
you.

Thanks,

Spencer

---

From: "Pars Mutaf" <[email-masked]>
Date: Fri, 12 Oct 2007 19:43:53 +0200

Hello,

I won't publish my SIP URI in a phone book allowing anyone to see it.
We already agreed on that.

I'll tell it to people that I know only. I'll tell it using a user friendly
mechanism called "pairing" : We meet each other with our cell phones,
and agree to exchange our contact information. So, the procedure is
under our control. Pairing is good for us also because it allows us to
exchange a secret key (note that this is already enough motivation for
the pairing idea).

The point is that, if I give you my SIP URI (using the pairing procedure)
then I can also give you my Mobile IPv6 home address using the same
pairing procedure. In other words, there is _no more resolution_ from
SIP URI to home IP address. You get them **concurrently**.

We have each other's SIP URIs and home addresses.
->SIP application is happy, it has the target SIP URI.
->Routing problem is solved by mobile IPv6.

My question was: do we need the SIP trapezoid in this case.

Thanks,
pars

Thanks,

---

From: [email-masked]
Date: Fri, 12 Oct 2007 14:32:51 -0400

From: "Pars Mutaf" <[email-masked]>

So your usage model is that you will only want to communicate with
people that you already know, and in most cases, have personally met.
This means that you have no need of a directory, as your SIP device
will be used to remember the URI of every person that you can call.

Note that this is much like how many mobile phone users use their
mobiles, but the opposite of the normal model of landline telephones,
where it is expected that the public can discover and contact you.

If you assume that each mobile has a fixed IPv6 address, then the
address-based URI will always reach the mobile.  And in that case, you
don't need a home proxy that translates an AOR into a contact URI --
in effect, that translation process has been moved down into the
network layer by the process of routing to that IPv6 address.

But it seems unlikely that an individual will have a fixed IPv6
address over the long term.  For one, it seems unlikely that *every*
network will provide uniform IPv6 mobility.  For another, what if the
user replaces his mobile?

Dale

---

From: [email-masked]
Date: Fri, 12 Oct 2007 21:30:57 +0300

I understand that the problem you want to solve is the following :

> Or, when you meet someone and want get your phones paired, you
> just type the target name because you have your cell phone in your hand.
> The phones get paired. You don't need to type a long SIP URI and
> Mobile IPv6 home address.

also mentioned in other email:

> and agree to exchange our contact information.

  I guess that what you want to avoid is to input in your phone the  
URI of the person you met, and instead automatically interchange URIs.

  In any case someone needs to enter something in their phone, either  
a URI, search keyword, TEL, etc to pair a contact...

SE

---

From: "Pars Mutaf" <[email-masked]>
Date: Mon, 15 Oct 2007 11:08:38 +0200

> will be used to remember the URI of every person that you can call.

Right. This model is the one being used today. Note that Bluetooth already
comes with a pairing solution.

We should make this idea technology independent and hopefully allow
users to pair their devices through the Internet, i.e. over long distances.
There are important motivations for that.

> network will provide uniform IPv6 mobility.

For another, what if the
> user replaces his mobile?

OK. We should use DNS perhaps to meet these requirements.
You can change your mobile IPv6 home address whenever you want
I have the DNS name of your device (obtained via pairing). Is it
acceptable to have fixed DNS name over long term?

There are also other interesting issues: With the proposed model,
I'm not sure if the operator needs to know my SIP URI.

Note also that the SIP URI is never transmitted in clear-text, we have
IPsec between the peers from the beginning (thanks to pairing).

But I guess these issues need to be discussed in more detail.

https://www1.ietf.org/mailman/listinfo/humanresolvers

Thanks,
pars

Dale

---

From: "Pars Mutaf" <[email-masked]>
Date: Mon, 15 Oct 2007 11:17:11 +0200

> URI of the person you met, and instead automatically interchange URIs.

Yes and also IPv6 home address, DNS name, IPsec key, why not e-mail address,
etc.

> a URI, search keyword, TEL, etc to pair a contact...

Right.

Thanks,
pars

SE
> >> I'm guessing that if you can't tell people your SIP AOR, then SIP is
> not
> >> for
> >> you.
> >
> >
> > Hello,
> >

---

From: Adam Roach <[email-masked]>
Date: Mon, 15 Oct 2007 11:09:56 -0500

Pars:

This is sounding like it's less and less a SIP problem at all. Based on 
what you say below, I think all you need is some additional vCard fields 
(one for voice SIP URIs, and maybe one for home IPv6 addresses -- but 
I'd pursue these as separate efforts, if I were you). You can then send 
these vCards around in OBEX, email, web pages, or whatever else makes 
sense. Note that OBEX over Bluetooth, IrDA, and/or SMS completely 
satisfies the requirements you describe below -- and these are already 
well-defined, mature, and widely deployed technologies.

Look at RFC 4770 to see how vCard extensions look.

/a

Pars Mutaf wrote:
>
>
> On 10/12/07, *Spencer Dawkins* <[email-masked] 
> <mailto:[email-masked]>> wrote:
>

---

From: "Pars Mutaf" <[email-masked]>
Date: Tue, 16 Oct 2007 11:23:56 +0200

> Look at RFC 4770 to see how vCard extensions look.

vCARD is OK.

I have asked a SIP question (I think this is the right place). Please answer

my question about SIP trapezoid, or if you don't know, that's OK.

As for your proposal for using Bluetooth or IrDA (discussion topic for
humanresolvers ML), this is of course a point of view. But I think you
missed
the point. This is clearly an IP layer problem and technology independent.
Why not use Wi-Fi? or WiMax? Why not use the Internet?

You really don't see the benefits?

/a
> >     <mailto: [email-masked]> for questions on current
> sip

---

From: Adam Roach <[email-masked]>
Date: Tue, 16 Oct 2007 13:37:45 -0500

> my question about SIP trapezoid, or if you don't know, that's OK.

Nothing mandates a trapezoid. That kind of deployment can be useful for 
certain architectures, but SIP can work just fine without it.

A trapezoid deployment can be useful for certain things; three come to 
mind immediately:

    * Rendezvous (although technically all you need for rendezvous is a
      triangle, not a trapezoid). Note that there are other potential
      solutions here, such as fixed IP addresses (including mobile IP),
      dynamic DNS, DHTs, and HIP.

    * NAT and firewall traversal (using the outbound extensions). This
      is only necessary if you're behind a NAT or a Firewall. Even then,
      there may be other solutions depending on what you are trying to
      accomplish, such as STUN/TURN, SOCKS, VPNs, uPNP, etc.

    * Network provided services. Most services can be successfully
      implemented in the terminal, but there seems to be a trend of
      pushing most services into the network (probably because it's
      difficult to charge people recurring fees for something their
      phone knows how to do). If you end up with users who have
      network-provided services, then you'll need to go through their
      servers.

If you don't need any of these things, then a trapezoid is unnecessary.

/a

---

From: "Henry Sinnreich" <[email-masked]>
Date: Tue, 16 Oct 2007 12:17:51 -0700

Adam's summary is the best of such that I have seen.

One could only add regarding NAT traversal, in P2P SIP networks many
folks are convinced that a large number of peers behind p2p-friendly NAT
can act as STUN and media relay servers for other peers and for p2p
clients as well.

This has however yet to be proven from deployment statistics on the
Internet, but for what it's worth, Skype has proven such an approach can
work.

Henry

-----Original Message-----
From: Adam Roach [mailto:[email-masked]] 
Sent: Tuesday, October 16, 2007 11:38 AM
To: Pars Mutaf
Cc: [email-masked]
Subject: Re: [Sip] SIP trapezoid (was Re: IETF solution forpairing
cellularhosts)

/a