Table Of Contents
New Feature in GGSN Release 5.2, Cisco IOS Release 12.3(14)YQ
Overview of GPRS and UMTS
This chapter provides a brief introduction to the 2.5G general packet radio service (GPRS) and the 3G Universal Mobile Telecommunication System (UMTS) technologies and their implementation in Cisco IOS GGSN software.
This chapter includes the following sections:
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New Feature in GGSN Release 5.2, Cisco IOS Release 12.3(14)YQ
Overview
GPRS and UMTS are evolutions of the global system for mobile communication (GSM) networks. GSM is a digital cellular technology that is used worldwide, predominantly in Europe and Asia. GSM is the world's leading standard in digital wireless communications.
GPRS is a 2.5G mobile communications technology that enables mobile wireless service providers to offer their mobile subscribers packet-based data services over GSM networks. Common applications of GPRS include the following: Internet access, intranet/corporate access, instant messaging, and mutlimedia messaging. GPRS was standardized by the European Telecommunications Standards Institute (ETSI), but today is standardized by the Third Generation Partnership Program (3GPP).
UMTS is a 3G mobile communications technology that provides wideband code division multiple access (CDMA) radio technology. The CDMA technology offers higher throughput, real-time services, and end-to-end quality of service (QoS), and delivers pictures, graphics, video communications, and other multimedia information as well as voice and data to mobile wireless subscribers. UMTS is standardized by the 3GPP.
The GPRS/UMTS packet core comprises two major network elements:
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Figure 1-1 shows the basic GPRS/UMTS network components with GGSNs implemented on Cisco 7200 series routers.
Figure 1-1
GPRS/UMTS Network Components with GGSNs Implemented on Cisco 7200 Routers
Figure 1-2 shows the network components with the GGSNs implemented on the Cisco MWAM in the Catalyst 6500 / Cisco 7600 platform.
Figure 1-2 GPRS/UMTS Network Components with GGSNs Implemented on the Cisco MWAM in the Catalyst 6500 / Cisco 7600 Platform
Note that, as Figure 1-1 and Figure 1-2 show, the RAN is made up of different components for 2.5G and 3G.
In a 2.5G environment, the RAN is composed of mobile stations that connect to a base transceiver station (BTS) that connects to a base station controller (BSC). In a 3G environment, the RAN is made up of mobile stations that connect to NodeB, which connects to a radio network controller (RNC).
The RAN connects to the GPRS/UMTS core through an SGSN, which tunnels user sessions to a GGSN that acts as a gateway to the services networks (for example, the Internet and intranet). The connection between the SGSN and the GGSN is enabled through a tunneling protocol called the GPRS tunneling protocol (GTP): GTP Version 0 (GTP V0) for 2.5G applications, and GTP Version 1 (GTP V1) for 3G applications. GTP is carried over IP. Multiple SGSNs and GGSNs within a network are referred to collectively as GPRS support nodes (GSNs).
Note
To assign mobile sessions an IP address, the GGSN uses the Dynamic Host Configuration Protocol (DHCP), Remote Authentication Dial-In User Service (RADIUS) server, or a local address pool defined specified for an access point configured on the GGSN. The GGSN can use a RADIUS server to authorize and authenticate remote users. DHCP and RADIUS services can be specified either at the global configuration level or for each access point configured on the GGSN.
In Cisco IOS Release 12.1(5)T and later, the GGSN on the Cisco 7200 series router (with an Integrated Services Adapter [ISA] card) supports IP Security (IPSec) protocol to provide data confidentiality, data integrity, and data authentication between participating peers.
On the Cisco MWAM installed in a Catalyst 6500 series switch / Cisco 7600 series Internet router platform, IPSec encryption is performed on the IPSec Virtual Private Network (VPN) Acceleration Services Module.
GPRS Interface Reference Model
The 2.5G GPRS and 3G UMTS standards use the term interface to label (or identify) the communication path between different network elements. The GPRS/UMTS standards define the requirements and characteristics of communication between different GPRS/UMTS network elements over these interfaces. These interfaces are commonly referred to in descriptions of GPRS/UMTS networks.
Figure 1-3 shows the interfaces that are implemented in the Cisco IOS GGSN feature:
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Figure 1-3 GPRS Interfaces Configured in the Cisco IOS GGSN Feature Implemented on the Cisco 7200 Series Router
Virtual Template Interface
To facilitate configuration of connections between the GGSN and SGSN, and the GGSN and PDNs, the Cisco IOS GGSN software uses an internal interface called a virtual template interface. A virtual template is a logical interface that is not tied directly to a specific interface, but that can be associated dynamically with a interface.
As with a physical interface on a router, you can assign an IP address to the virtual template interface. You can also configure IP routing characteristics on the virtual template interface. You are required to configure certain GPRS/UMTS-specific elements on the virtual template interface, such as GTP encapsulation (which is necessary for communicating with the SGSN) and the access list that the GGSN uses to determine which PDNs are accessible on the network.
Access Points
The GPRS/UMTS standards define a network identity called an access point name (APN). An APN identifies the service or network to which a user can connect from a GGSN in a GPRS/UMTS network.
To configure APNs, the Cisco IOS GGSN software uses the following configuration elements:
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For more detailed information on access-point configuration, refer to the "Configuring Access Points on the GGSN" section.
Benefits
The 2.5G GPRS technology provides the following benefits:
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In addition to the above, the 3G UMTS technology includes the following:
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GGSN Release 5.0 and later is a fully-compliant 2.5G and 3G GGSN that provides the following features:
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New Feature in GGSN Release 5.2, Cisco IOS Release 12.3(14)YQ
Cisco GGSN Release 5.2 and later introduces, in conjunction with the Cisco CSG and Cisco Diameter/DCCA support, real-time credit-control for prepaid users and service-aware billing for postpaid and prepaid users.