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With estimates of more than 800 million customers today, Global System for Mobile Communications (GSM) is the world's leading digital wireless communications standard. GPRS is a new data service that brings packet data IP-based services to the worldwide GSM subscriber base. GPRS gives subscribers continuous and fast access to IP-based services and is a vital step toward third-generation (3G) converged wireless and IP networks.
GPRS-enabled networks offer "always-on," higher capacity, Internet-based content, and packet-based data services. GPRS uses a packet radio principle and can be used for carrying end users' packet data protocol (such as IP or Point-to-Point Protocol [PPP]) information both from and to a GPRS terminal and to and from other GPRS terminals or the Internet.
GPRS facilitates access to applications normally available on a user's desktop, such as Web browsing, e-mail, database queries, chat, and stock updates. Other new applications for GPRS include file transfer, multimedia messages, home automation, and location-based services.
Cisco IP and wireless expertise brings together the world of IP and GSM to deliver advanced high-quality, secure GPRS services to mobile subscribers. As shown in Figure 1, the Cisco GPRS solution offers new opportunities to generate revenue from the mobile 2.5G and 3G services. The solution is based on proven Cisco IOS Software and IP router technology, and provides low cost, reliable, and highly secure GPRS connections. Cisco IOS Software within the Cisco GGSN provides a sophisticated suite of networking capabilities that reside at the heart of internetworking devices. The Cisco GGSN and the data network components interoperate with external packet data networks, and connect to the Cisco Serving GPRS Support Node (SGSN) using an IP-based GPRS backbone network. The Cisco GGSN provides IP connectivity to public services (Internet, Wireless Application Protocol [WAP], and Multimedia Messaging Service [MMS]) and corporate VPNs.
The Cisco solution provides the following components that are required to create the GPRS backbone network: the Cisco GGSN, the border gateway, comprehensive security, the full suite of servers (authentication, Domain Name System [DNS], Dynamic Host Configuration Protocol [DHCP], cache engine, and directory server), the Cisco Service Selection Gateway (SSG), Cisco PIX® Firewall, and the network management system (NMS). The solution allows mobile operators to provide value-added services such as VPN connectivity and other enhanced services to enterprises, Internet service providers (ISPs), and consumers.
The primary Cisco GGSN features include:
The following is a description of the key features offered by the Cisco GGSN:
GTP tunneling is a GPRS-specific protocol designed to tunnel user data and signaling between Gateway GPRS Support Nodes (GGSNs) in the GPRS backbone network. GTP encapsulates all PPP data packet protocol data units (PDUs). The GTP tunnels and paths can be established between two Cisco GGSNs using any types of physical network interfaces that support IP as GPRS Gn (Gn—the interface specified between the SGSN and the GGSN) and, Gp (, Gp - interface specified between SGSN and GGSN belonging to different GPRS networks) link between GPRS networks belonging to different public land mobile network [PLMNs]) interfaces.
The Cisco GGSN supports interworking with networks based on the IP. Internet or intranet interworking is required whenever a PLMN supporting GPRS and any other network is involved in the execution of a GPRS service request.
Key functions performed here are GPRS-defined relay, routing, address translation and mapping, encapsulation, tunneling, and DHCP/RADIUS proxy.
With GPRS, a GPRS tunnel is determined by a Cisco SGSN-GGSN pair and characterized by the tunnel ID (TID). All messages relative to a user are routed inside each tunnel all the way to the ISP and intranet.
The selection of the Cisco GGSN is performed by the Cisco SGSN, depending on the destination desired.
This function collects data necessary to support subscription or traffic fees. The Cisco GPRS solution supports prepaid and postpaid billing.
The quality of service (QoS) mechanism implemented in Cisco GGSN 1.4 uses a "canonical" QoS mapping. Where the GPRS QoS classes (defined in the standards) are mapped into "canonical QoS classes", those classes are then used to mark the IP packets carrying GTP messages or user data. The DSCP (Diff Serv Code Points) field in the IP header is used as defined in the Differentiated Service Architecture for IP networks. In release 3.0, a new mapping option is available; this new mapping uses the users delay class as the main criteria. The GPRS QoS classes are mapped to delay classes as described in GPRS R97/98 specifications.
Cisco routers provide a variety of switching algorithms, or paths, to optimize IP packet processing. Therefore, switching paths minimize the amount of time it takes for the router to forward a packet from its incoming interface to an outgoing interface.
Starting with Cisco GGSN 3.0, to scale and support more GPRS PDP contexts, an aggregate route can be used to handle user data packets for multiple PDP contexts (instead of a host route for each PDP context). Using this feature, mobile stations that host routes with the same prefix will be aggregated into one route.
The Cisco GGSN supports the IPv4 and PPP PDP type.
The different types of PPP support on the Cisco GGSN are differentiated by where the PPP endpoints occur within the network, whether Layer 2 Tunneling Protocol (L2TP) is in use, and where IP packet service occurs.
PPP regeneration on the Cisco GGSN supports the use of an IP PDP type in combination with PPP and L2TP. For each IP PDP context that the Cisco GGSN receives at an access point that is configured to support PPP regeneration, the GGSN regenerates a PPP session. The Cisco GGSN encapsulates any tunnel packet data units (TPDUs) in PPP and L2TP headers as data traffic and forwards them to the local network server (LNS).
PPP regeneration on the Cisco GGSN implements virtual routing and forwarding (VRF) to handle overlapping IP addresses.
The Cisco GGSN solution provides extensive VPN technologies support: IPsec, L2TP, GRE, 802.1q, MPLS, with overlapping IP addresses and APN mapped to a VPN.
The GTP server-load-balancing (SLB) feature is based on Cisco IOS Software Server Load Balancing (SLB), which allows users to represent a group of network servers as a single server instance, to balance the traffic to the servers, and to limit traffic to individual servers. The SLB feature provides load balancing and failover mechanisms that allow a scalable Cisco GGSN implementation and increase the robustness of the network. With a virtual Cisco GGSN providing load balancing of the GTP traffic to multiple real Cisco GGSNs, software upgrades can be done without any disruption to service.
The virtual APN feature on the Cisco GGSN allows multiple users to access different physical target networks through a shared APN access point on the Cisco GGSN. The virtual APN feature reduces the amount of APN provisioning required by consolidating access to all real APNs through a single virtual APN at the Cisco GGSN. The virtual APN feature provides the following benefits to the GPRS operators:
Cisco has added GTP Director Module (GDM) as part of the Cisco GGSN feature set in the Cisco IOS Software. GDM extends some of the benefits that are available on a Cisco GGSN to GPRS environments where third-party GGSNs are implemented. These benefits include reducing APN provisioning requirements in the GPRS PLMN while also providing simple, round-robin load balancing for the Cisco GGSNs. A network using GDM has the added benefit of the Cisco Hot Standby Router Protocol (HSRP) to support increased network availability using a backup GDM router.
IP routing specifies that IP datagrams travel through an internetwork one router hop at a time. The entire route is not known at the outset of the journey. Instead, at each stop, the next router hop is determined by matching the destination address within the datagram with an entry in the routing table of the current node. The involvement of each node in the routing process consists only of forwarding packets based on internal information. IP does not provide for error reporting back to the source when routing anomalies occur. This task is left to another Internet protocol: the Internet Control Message Protocol (ICMP).
Cisco GGSN supports a full RADIUS-proxy to provide the full AAA facilities.
Among the RADIUS features Cisco GGSN supports are authorization, accounting, interim accounting-update, packet of disconnect, anonymous access, and so forth. The RADIUS interface is fully compliant to Internet Engineering Task Force (IETF) RFC and 3GPP specifications security features.
Table 1 lists several security features added to Cisco GGSN 3.0 to cope with MS related attacks. Those features are meant to protect MSs against external attacks, but also to protect the network from MS attacks.
Table 1 The Cisco GGSN 3.0 Security Features
Network management functions provide mechanisms to support operations, administration, and management (OA&M) functions related to GPRS. The Cisco GGSN management has a wide range of console and Simple Network Management Protocol (SNMP) management tools designed to reduce operations costs. Cisco GGSN R3.0 on a 7206VXR/NPE-400 is supported by CiscoWorks for Mobile Wireless, which is equipped with fault management, APN management, and configuration management for the Cisco GGSN. CiscoWorks for Mobile Wireless is a suite of element management system (EMS) applications that enhances the delivery of new mobile wireless services. It is based on CiscoWorks and will address the element management requirements of mobile operators and provide FCAPS functionality as mobile operators transition their service delivery networks from 2G circuit-based traffic to 2.5G and 3G IP-based services. For more details on CiscoWorks for Mobile Wireless see http://www.cisco.com/en/US/products/sw/ cscowork/ps2422/index.html.
The Cisco GGSN 3.0 software runs on the Cisco 7206 VXR router, as shown in Figure 2, and requires a minimum of 48 MB Flash, 256 Mbytes DRAM, and 32 MB SRAM of memory.
Cisco GGSN 3.0 is compliant with the following standards:
Cisco GGSN 3.0 on a Cisco 7206VXR with Cisco NPE 400 Network Processing Engine with 512 MB memory can support up to 180,000 PDP sessions and 160 Mbps raw throughput. The actual capacity is dependent on the specific configuration of a customer GGSN, memory capacity, and the applications and features that are active on it.
Table 2 provides ordering information for the Cisco GGSN 3.0 with Cisco IOS Software. Three software versions are available for customers:
Export restrictions may apply for the Cisco GGSN 3.0 3DES strong encryption software for export to some countries. Please check on export restrictions on Cisco.com.
Cisco is a leader in data networking, and a large percentage of today's data traffic flows through Cisco networks. Cisco is the first to implement the Cisco GGSN with the Cisco SGSN from multiple partners and to offer a complete GPRS solution for the GSM wireless operators. The Cisco value proposition is: Get the best company for radio and get the best company for data in your infrastructure.
The Cisco GGSN functionality embedded in the Cisco IOS Software differentiates the Cisco GGSN solution from other industry alternatives. The Cisco IOS Software within the Cisco GGSN provides a sophisticated suite of networking capabilities that reside at the heart of internetworking devices. The Cisco GGSN solution, combined with its routing capability, offers the same level of quality, reliability, and scalability that has made Cisco a leader in the Internet and data networking industry.
Cisco allows the operator to deploy a 2.5G GPRS solution, which will position them for 3G. The 2.5G-to-3G migration for the Cisco GGSN is simply a software upgrade. In addition to the standard features, Cisco GGSN offers value-added features, mainly aimed at corporate mobile users, such as VPN services, dial-like services, and consumer services.
By implementing Cisco GPRS products and related solutions, mobile operators can optimize their networks today by deploying high-quality mobile voice and data services. They can also benefit from new operating efficiencies, peer-to-peer IP-based architecture for scalability, and IP standard interfaces to billing (prepaid and postpaid) and customer support. Moreover, the Cisco GGSN 3.0 on a Cisco 7206VXR/NPE-400 is supported by CiscoWorks for Mobile Wireless network management, which is equipped with fault management, APN management, and configuration management for the Cisco GGSN.
Cisco is unmatched in the breadth and depth of its access to resources, shared intellectual capital, and leading data and telecommunications products and expertise. This combination enables Cisco to provide the highest quality available in carrier-class support, solutions, and vision for its service-provider customers. Cisco service and support solutions enhance the value of your investment in network infrastructure, resulting in an overall reduced cost of doing business. Now you can deliver fully on the promise of internetworking technology, with the backing of world-class support and service.
For more information about Cisco's mobile wireless products and solutions, go to www.cisco.com/go/mobile .
Posted: Thu Sep 25 10:13:58 PDT 2003
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