Subject: [Sipping] 3GPP requirements to SIP

From: "Miguel A. Garcia" <[email-masked]>
Date: Wed, 10 Oct 2001 10:43:23 +0300

Hi:

In the last IETF meeting our Area Director requested 3GPP to write down all the requirements that 3GPP has to SIP. 

A few people have gathered those requirements and put them into an Internet Draft. The I-D has been recently submitted to the IETF. It might take a few hours to be available in the repositories. In the meantime, you can download the I-D from:

http://standards.ericsson.net/sip/drafts/draft-garcia-sipping-3gpp-reqs-00.txt

Regards,

       Miguel
-- 
Miguel-Angel Garcia                     Oy LM Ericsson AB
                                        Jorvas, Finland
mailto:[email-masked]     Phone:  +358 9 299 3553
mailto:[email-masked]        Mobile: +358 40 5140002

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---

From: Paul Kyzivat <[email-masked]>
Date: Wed, 10 Oct 2001 19:08:50 -0400

While reading through this document I came up with a number of
questions. Note that I have no ax to grind and no stake in this game, I
am simply interested.

- The following:

  "The visited network contains a SIP outbound proxy to support the UA.
   The SIP outbound proxy in the visited network may translate locally
   dialed digits into international format,..."

  seems backwards to me. It implies that the translation of dialed 
  numbers will vary depending on where I am visiting. This seems
  less than useless. Why would I want to be subject to the whims of 
  the place I am visiting? This just makes it harder to use, and 
  ultimately the call will be processed through my home network 
  anyway.

- "The terminals first connect to the GPRS network to get an
   IPv6 address. In order to do this, the terminals must perform a
   (GPRS) Attach procedure followed by a (GPRS) PDP Context Activation
   procedure."

  Why? The whole point of IPv6 is that there are enough addresses for
  every possible device to have one permanently assigned.

- The logic of requiring registration for initiating calls has been
  flagged before. I won't say more because others can say it better.
   
	Paul Kyzivat
	Cisco Systems

---

From: "Dean Willis" <[email-masked]>
Date: Thu, 11 Oct 2001 00:26:08 -0500

>   every possible device to have one permanently assigned.

I can't resolve the other questions, having staggered over a few myself, but
I'll take a shot at this one. Maybe three shots -- enough lead in the air
and maybe we can have duck for dinner.

Because the GPRS layer 2 mechanism doesn't support global roaming and Mobile
IP is a pig-dog for latency and nobody wants a dynamically defined  /128 BGP
route for every mobile phone in the world cluttering up the routing tables?

--
Dean

---

From: "Miguel A. Garcia" <[email-masked]>
Date: Thu, 11 Oct 2001 09:04:52 +0300

> questions. Note that I have no ax to grind and no stake in this game, I

Fair enough.
 
>   ultimately the call will be processed through my home network

No, I don't agree with you. You can always dial the full international
number, and this number does not depend on the location you are. This
is how it works in GSM today. If I visit another country, and my address
book contains a fully international number, then I can dial that number
without modifications.

If I am visiting another country, I can dial a local number, as any local
user would do. This number will be internationalized by the SIP outbound
proxy, and send it to the home network. By doing this you achieve a few
things:
- First, the user can dial fully international or local numbers.
- The home network always gets fully international numbers. Therefore,
  it does not need to know the local numbering plans all around the world.
- The SIP outbound proxy needs to know about the local numbering plan in 
  its own network and country. Nothing wrong with this, it is only in its
  own network.

>   every possible device to have one permanently assigned.

Typically the IPv6 address belongs to the address space of the visited
network. Therefore, it changes when you change your visited network,
that is, when you roam to another visited network. There is GPRS procedure 
get an IP address, similar to what DHCP does. The statement above only
says that the terminal needs to get an IP address before doing anything
else. 

>   flagged before. I won't say more because others can say it better.

Me neither.

Regards,

         Miguel

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From: Juha Heinanen <[email-masked]>
Date: Thu, 11 Oct 2001 12:53:19 +0300

> route for every mobile phone in the world cluttering up the routing tables?

this goes off thes sipping list, but why then all that talk about ipv6
and mobile ip for all ip mobile networks?  why not simply standardize on
hip that solves all these problems?

-- juha

---

From: Paul Kyzivat <[email-masked]>
Date: Thu, 11 Oct 2001 09:19:55 -0400

Responses inline.

	Paul

> book contains a fully international number, then I can dial that number

Sure. But why would my address book contain international numbers.
When I am at home I don't need international numbers, so the only
international numbers I am likely to know are for remote places I call.

> - First, the user can dial fully international or local numbers.

This is true both ways. It is only a matter of which local numbers
I can use. Personally, I would rather have a consistent dialing context
wherever I am than have one that changes as I move.

Suppose I am near the boundary of an area code, and also near
a cell boundary, so that one side I am in my home region and on 
the other side I am roaming. I could end up in a situation where just
walking across the room is enough to change the dialing plan.

>   it does not need to know the local numbering plans all around the world.

I didn't suggest it should. 

"Drage, Keith (Keith)" wrote:
> 
> Regarding the question on dialled numbers, Miguel has answered the question,
> but it is worth pointing out that the reason for the requirement IS to keep
> it the same as existing mobile phones.

Well, I suppose there may be some justification for compatibility.
But it seems to me it is being compatible with a mistake. Isn't part
of this exercise to fix the mistakes of the past?

> 
> Therefore the user requirement is to dial a E.164 subscriber or national
> number, and have it interpreted as a E.164 subscriber number or national
> number according to the usage of the visited network rather than the home
> network. When the user walks down the street and sees a national number
> displayed (on the side of taxi or whatever) when he dials those digits he
> will get the taxi firm, rather than some number in the home network.

And of course he no longer has any clue whether the numbers he is
dialing will be considered local calls to him or not. He may need
to dial international numbers to make local calls, and local numbers
will be long distance calls.

And of course, the numbers one sees posted often aren't complete
numbers according to the local dialing plan either. In the USA there
is the question of whether to dial "1" or not, and sometimes the
area code is required but not posted. Once you start moving between
countries the situation gets worse. So the likelihood of being able
to dial a local number I see posted is often slim.

"Miguel A. Garcia" wrote:
> network.

Why? Only because you are assigning them dynamically.
If the IPv6 address went with the phone, then it would probably
belong in the address space of the phone manufacturer or
distributor.

> Therefore, it changes when you change your visited network,
> that is, when you roam to another visited network.

You are creating this problem for yourself.
If it was fixed, of course it wouldn't change when you roam.

> There is GPRS procedure

So, if I choose to get an IPv6 address permanently assigned to my
phone everything should still work?

---

From: "Miguel A. Garcia" <[email-masked]>
Date: Thu, 11 Oct 2001 16:35:47 +0300

> international numbers I am likely to know are for remote places I call.

As far as I can tell you, my address book in my GSM phone contains ONLY international numbers. Therefore, I can use my address book from any country in the world where I have GSM connectivity (and roaming agreement). 

I suspect that this is a common practice in Europe for roamers: store only international numbers in your phone book.

> walking across the room is enough to change the dialing plan.

Then you should use the fully international number and forget about the problem.

> of this exercise to fix the mistakes of the past?

Well, as I said before, I think this is a new feature of GSM. It is wise to fix errors from the past, but this is considered not an error.

> will be long distance calls.

In GSM you can always dial a plus sign (+) to indicate that the number is international. This is even reflected in the Tel URL RFC 2806.

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From: Henning Schulzrinne <[email-masked]>
Date: Thu, 11 Oct 2001 09:38:21 -0400

> phone everything should still work?

There is a misunderstanding here. IPv6 still has to assign addresses
based on where you are in the network (you can keep your home address if
mobile IPv6 is used). Otherwise, there's no way to route packets to you.
After all, the routing system can't keep track of every individual
mobile.

I suspect the confusion arises since IPv6 does often, but not always,
keep *part* of the IPv6 address constant; the lower bits are permanently
assigned (e.g., based on your MAC address), with the routing prefix
allocated dynamically, depending on where you are. That way, you can
send packets within your local network without any address assignment
("link-local addresses").

This feature has nothing to do with 3G. (I'm grossly simplifying the
various IPv6 autoconfiguration modes here.)