Subject: [Sipping] 3G usage scenarios

From: Rohan Mahy <[email-masked]>
Date: Thu, 08 Nov 2001 09:56:28 -0800

Hi,

I've been thinking about the 3G model as described in the requirements, and 
asking what *value* each of the actors is providing.  The good news is that 
the value provided by both the visited and home networks is compelling for 
the user.  So, what service is the visited network providing and what 
service is the home network providing?

The visited network provides GPRS access, reserved QoS on the radio 
interface, access to emergency services, sends a BYE on behalf of the 
mobile when the radio link is lost, and handles Via/Route/RR 
"compression".  The home network provides location/registration services 
for inbound SIP requests, and centralized billing.

So is there any harm in bypassing part of the architecture from time to 
time?  Can I  negotiate GPRS access to a visited network, and then use 
best-effort QoS to send instant messages and possibly audio directly to a 
friend using a SIP UA on her computer (bypassing the home and visited SIP 
servers)?  Can I register with the home network to receive incoming calls, 
but then use a credit card or electronic cash payment system to pay 
directly for GPRS, gateway access, and reserved QoS (bypassing the home 
network for outgoing INVITEs)?   There is no reason this shouldn't work 
technically, and I think it is a requirement that the system is flexible 
enough to work in this way.

Also, what is the relationship between the home and visited 
networks?  There is an implicit trust here, but the trust is based on 
mutual financial advantage.  Each network has enough information to 
"verify" billing to prevent/discourage cheating.  Therefore, I suggest that 
signalling between these two networks should reflect the financial 
relationship.  In other words, the home network should have a mechanism to 
indicate that it will reimburse the visited network for a particular 
user.  This could be done once at registration time.  The visited network 
could subscribe to this information and be notified when it changes (the 
user's terminal is stolen, the prepaid card has run out of money, 
etc.)  The visited network could also take responsibility to 
register/deregister on behalf of mobile users, and to terminate sessions 
that have ended abruptly.  The visited network is also financially incented 
to disconnect calls that will no longer be reimbursed.  By dividing 
responsiblity between the two networks, the system becomes less complex and 
more robust.  The home network can concentrate on billing and 
authorization, and does not otherwise need to manage call state.

comments welcome.

thanks,
-rohan

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---

From: "Roy, Radhika R, ALCTA" <[email-masked]>
Date: Thu, 8 Nov 2001 13:49:43 -0500

Hi, Rohan:

We can generalize the 3GPP requirements for mobility support.

1. Home network and visited network

2. Services that need to be provided by the network

2a. Home network, 2 b. Visited network

3. Mobility: User mobility, Terminal mobility, Services Mobility and Service
provider mobility.

Keeping the above things in perspectives, scenarios are created.

You are right in analyzing the scenarios, however, more generalized cases
need to be created. You analysis is in the right direction.

I have some quick comments inline [RRR].

I like to see more inputs from 3GPP folks as well.

Best regards,

Radhika R. Roy

-----Original Message-----
From: Rohan Mahy [mailto:[email-masked]]
Sent: Thursday, November 08, 2001 12:56 PM
To: [email-masked]
Cc: [email-masked]
Subject: [Sipping] 3G usage scenarios

Hi,

"compression".  

[RRR] Only a part of the scenarios if both caller and called party are in
the visited network. If they are in different networks, the things will be
different.

The home network provides location/registration services 
for inbound SIP requests, and centralized billing.

[RRR] Can be little more than as well. For example, some services may also
be provided in certain situations.

[RRR] Each of these cases require detailed attention. We will only focus the
impact of the SIP call control signaling layer.

[RRR] You are almost there. Each of these events need to be captured while
event packages will be created.

comments welcome.

thanks,
-rohan