Subject: RE: [mobile-ip] Involvement w. 3Gs? (context transfer from Seamob y)

From: Ken Rehbehn <[email-masked]>
Date: Thu, 12 Apr 2001 20:29:11 -0400

> >At an IEE conference in London a 
> >few weeks ago, a paper was given announcing a plan to do inter-GGSN
> >GPRS transfer (called GPRX). The R99 spec for 3GPP specifies 
> that this
> >should be done through mobile IP, but no 3GPP vendor implements it
> >and none of the mobile operators are deploying it. They have
> >shown no interest in working with IETF to resolve this.
> 
> Do you have any insights into why they would want to specify a new
> mechanism (GPRX)? After all as you said the R99 spec does include
> support for an FA in the GGSN and inter-GGSN transfers could be
> handled between the FAs. I am sure the Mobile IP WG would be able to
> satisfy the requirements for an inter-GGSN /FA transfer that are
> specific to 3GPP. Anyone here care to throw some more light on GPRX
> and why you cannot do this with Mobile IP?
> 

This sounds like the GRX.  It is not a new protocol.

The GSM Association developed this as an agreement between GPRS operators to
facilitate interconnection of disparate GPRS systems in support of roaming
users.  They called this the GPRS Roaming Exchange (GRX) and invited various
organizations, such as ISPs, to bid on supplying the service.  A good
example of one is http://www.sonera.fi/english/solutions/grx/.

The agreement uses off-the-shelf IP routing facilities (BGP4 and DNS) to
interconnect private IP-based radio access networks using routing policies.
The IP packets containing the GPRS GTP tunnels flow across these network
borders when a customer roams.  

The entire mechanism is transparent to the roaming user (until they get the
bill!).

Ken

---

From: "Tim Clifford" <[email-masked]>
Date: Fri, 13 Apr 2001 10:00:17 -0400

Ken
 a few comments on the GRX, I wrote UUNET's response to the RFP.
- there's actually little emphasis, the *specs* actually question its
viability, about using standard IP mechanisms for the GRX.  There's
currently significant question about the way that things like DNS would be
implemented and its a *private* DNS, not part of the Internet DNS
- the interconnection is between GPRS PLMN, not "IP-based radio access
networks."  I suspect the GRX was based on the R98 spec, which states
(section 5.4.2) that an"..inter-PLMN backbone network can be a Packet Data
Network, e.g., the public Internet or a leased line." It was pretty much up
to the respondees to the RFI how to provide the service; mostly I believe
providers went the IP VPN route

As to why it was decided to use these non-Internet mechanisms, I don't
expect there's a technical reason.

tim

-----Original Message-----
From: [email-masked]
[mailto:[email-masked]]On Behalf Of Ken Rehbehn
Sent: Thursday, April 12, 2001 8:29 PM
To: [email-masked]'
Subject: RE: [mobile-ip] Involvement w. 3Gs? (context transfer from
Seamob y)

Ken