Project
IEEE 802.21 Media Independent Handover Services
<http://www.ieee802.org/21/>
Title
Comments on Information Service (IS) Reference Model for 3G roaming case
Date
Submitted
October, 2005
Source(s)
Stefano Faccin
Re:
21-05-0xxx-00-0000-Higher_layer_Requirements_Information_Service 3G roaming
Abstract
This contribution contains some comments on the IS model for the 3G roaming case.
Purpose
To generate discussion to ensure that the Information Service reference model cover the 3G
roaming case.
Notice
Release
Patent
Policy
This document has been prepared to assist the IEEE 802.21 Working Group. It is offered as a basis for
discussion and is not binding on the contributing individual(s) or organization(s). The material in this
document is subject to change in form and content after further study. The contributor(s) reserve(s) the right
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The contributor is familiar with IEEE patent policy, as outlined in Section 6.3 of the IEEE-SA Standards
Board Operations Manual <http://standards.ieee.org/guides/opman/sect6.html#6.3> and in Understanding
Patent Issues During IEEE Standards Development <http://standards.ieee.org/board/pat/guide.html>.
1
1 Introduction
The purpose of this document is to identify one scenario that has impact on the IS reference
model and that needs to be considered. The document is based on 21-05-0348-01-0000Req_Higher_layer_IS.doc.
2 3G Roaming Model
In 3GPP roaming scenarios, in most cases the roaming terminal obtains IP connectivity in the
home network. Specifically, for GPRS the GGSN is often located in the home network and,
respectively, the PDG for 3GPP-WLAN IW will be most often located in the home network for
the same reasons the GGSN is.
In such case, the terminal has no direct IP connectivity with the visited network. IP connectivity
with the visited network takes place through the home network only. However, the terminal may
need to access efficiently the IS from an IS function in the visited network. Forcing packets to
go to the home network first, then to the IS Function in the visited network, and then perhaps to
the IS Function in the home network (e.g. as described in the current IS model in 21-05-034801-0000-Req_Higher_layer_IS.doc) is not efficient. The IP connectivity with the current model in
the 3G roaming scenarios with anchor point in home network may be interpreted as in the
following picture.
2
Home Network
Single hop Model
Visited Network
UE
Network IS Provider (NISP)
802.21
IS Function
(Client)
802.21
IS Function
(Server)
Ia
Information
Database
Ix
Multi hop Model
Point where UE gets IP
connectivity
Home Network
Visited Network
UE
Network IS Provider (NISP)
Proxy NISP
802.21
IS Function
(Proxy)
802.21
IS Function
(Client)
802.21
IS Function
(Server)
Information
Database
Ia`
Ia
Ix
Figure 2.1: Information Service Reference Model
The IS model need to cater for such scenario more efficiently. In reality the model already cater
for such scenario if the model is interpreted as in the following picture.
Multi hop Model
Point where UE gets IP
connectivity
HOME Network
UE
VISITED Network
Network IS Provider (NISP)
Proxy NISP
802.21
IS Function
(Proxy)
802.21
IS Function
(Client)
Ia
802.21
IS Function
(Server)
Ia`
Information
Database
Ix
3
Alternatively, the model can be depicted as in the next picture.
Single hop Model
Network IS Provider (NISP)
UE
802.21
IS Function
(Client)
802.21
IS Function
(Server)
Ia
Multi hop Model
Proxy NISP
UE
Ix
Network IS Provider (NISP)
802.21
IS Function
(Proxy)
802.21
IS Function
(Client)
Information
Database
802.21
IS Function
(Server)
Ia`
Ia
Information
Database
Ix
Multi hop Model
UE
Network IS Provider (NISP)
802.21
IS Function
(Client)
Proxy NISP
Ia`
Ia
802.21
IS Function
(Server)
Information
Database
Ix
802.21
IS Function
(Proxy)
Network where UE gets
IP connectivity
Local network
Ia : Interface between UE and Network IS provider
Ix: Interface between IS function and Information Database
Ia`: Interface between two Network IS providers
Figure 2.1: Information Service Reference Model
A similar scenario applies when the UE is connecting to a third party network, e.g. enterprise,
using an IPSec VPN. With IPSec VPN typically no packets outside the secure tunnel are
allowed. Therefore, to all effects, the UE is gaining IP connectivity in the third party network
(e.g. enterprise), and not in the network providing access connectivity, since all packets sent by
the UE are routed through the home network.
3 Implications On Requirements
Discovery of IS Function in visited network must be possible even if the UE does not have direct
IP connectivity to the visited network (i.e. it needs to pass through the home/remote network).
This may mean that the UE provides enough information to the IS Fucntion in the home
network (in this case the Proxy IS Function) to discover/contact the IS Function in the visited
network.
The security model is also impacted, since it is considerably different than in the case the UE
can directly talk with the IS Function in the visited network. Establishment of an SA between the
US and the IS Function in the visited network may not be possible.
4
5