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This chapter provides an overview of the Cisco Mobile Exchange (CMX) and contains the following sections:
Cisco Mobile Exchange (CMX) is a framework of solutions that addresses the interface between the evolving radio access network and a wide array of Internet services offered by Internet Protocol (IP) networks. The CMX framework provides flexible solutions to mobile operators, application providers, and system integrators that enable them to offer value-added data services to mobile subscribers. These services include mobile banking, web surfing, location services, and electronic payments. The challenge for mobile operators is cost-effectively managing these services, providing secure access to high revenue customers, and evolving their networks as wireless technologies advance. The Cisco Mobile Exchange provides the required flexibility to effectively meet these demands using field-proven hardware and software applications.
The key benefits of the CMX are:
The CMX framework incorporates the following components (Figure 1-1):
Together, these components create a flexible framework of solutions for mobile operators to generate revenues from their 2G, 2.5G, or 3G mobile packet infrastructures. They offer the flexibility of modular design and the reliability of proven platforms.
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Tip Go to www.cisco.com/go/mobile for more information about Cisco Mobile Exchange components. |
The packet gateway is the interface between the mobile infrastructure and standard IP networks. A gateway translates between access-specific protocols of the radio access network (RAN) and the access-independent world of the Internet. Mobile operators transmit IP packets through the air using one of these standards:
Many first-generation packet gateways do not scale to accommodate profitable numbers of users and sessions. For mobile operators seeking to upgrade their first-generation packet gateways, Cisco offers both GGSN and PDSN gateways on Cisco Internet routers and on Catalyst series switches. These gateways offer scalability features an order of magnitude beyond previous solutions.
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Note Cisco Mobile Exchange provides support for GPRS networks with plans to support PDSN networks in the future.This document focuses on the CMX solution for GPRS networks. For more information on CMX support for PDSN networks, go to www.cisco.com/go/mobile. |
Since mobile subscribers pay for content, mobile operators need to tailor data, voice, and video services for each subscriber. Personalized services require higher-layer network intelligence that accommodates the unique requirements of mobile networking. The CMX satisfies these requirements.
Currently, Cisco Mobile Exchange offers the following mobile services:
Each service supplies a critical function for enabling profitable content-based services.
A key capability that helps service providers brand their services and lay the foundation for future growth is service selection. Service selection lets mobile operators intervene in data flows and determine particular services that subscribers can access. It enables a common look and feel to users and a uniform billing infrastructure. This capability allows a provider to both exercise discrete control over service access and enable self-provisioning to reduce operational costs, speed service availability, and recover lost revenues. For example, a mobile operator might gather substantial revenue from their messaging services. However, if a subscriber logs onto a third-party instant messaging server, the provider loses revenue for those transactions. Using service selection, the provider can provide access to alternate messaging services only if the subscriber pays a fee. Operators need the ability to support several billing structures based on particular services and market. Cisco provides this capability with its service selection technologies.
Cisco Service Selection Gateway (SSG) and Service Edge Subscriber Manager (SESM) together allow providers to control what subscribers can do based on their payments and privileges. The SSG presents a Web portal, offering service icons that the subscriber can click to access their subscribed services (see Figure 1-2 for example). It can be customized to offer a subset of the total service portfolio, display targeted advertising, or with a VPN service, appear as a corporate intranet page. The SESM enables self-provisioning, where subscribers log onto a Web page to buy services or check their service usage. Together, the SSG and SESM reduce operational expenditures and increase subscriber satisfaction through more efficient, faster service.
Content monitoring or content billing examines packets to obtain higher-layer information such as particular URLs, domains, or file names. With this information, a mobile operator can bill for usage-based services or gather data for market research.
For example, an enterprise provides its employees with a personal digital assistant (PDA) and mobile access service. Because the provider has usage-based billing, the enterprise does not want to pay for personal activities. With content monitoring, the network can determine whether an employee is checking email (a service the enterprise pays for) or checking sports scores (a service the employee pays for). The mobile operator can split the bill between the enterprise and the employee. This helps enterprises contain network access costs. It also encourages them to sign up for new mobile services with full confidence in their usefulness to the business.
Content monitoring allows the provider to track and record subscriber usage in terms of user identity, traffic volume, content, and applications. All CMX systems can be integrated with pre-paid or post-paid billing systems for maximum business flexibility.
The growing demand for TCP/IP-based application services such as e-commerce, video, and e-mail is motivating companies to increase the availability and scalability of network and server systems. Cost containment is also driving the need for intelligent server switching to scale the server complex and caching techniques to conserve WAN bandwidth.
The Cisco server load balancing (SLB) feature is an IOS feature that intelligently balances the load of user traffic across multiple TCP/IP application servers. This feature ensures continuous, high availability of content and applications with proven techniques for actively managing servers and connections in a distributed environment. By distributing user requests across a cluster of servers, SLB optimizes responsiveness and system capacity and reduces the cost of providing large-scale Internet, database, and application services. In addition, its integrated security capability protects servers from unauthorized access.
The SLB feature offers enterprise customers and ISPs a network-based intelligent server solution. The SLB feature tracks network sessions and server load conditions in real time, directing each session to the most appropriate server and maintaining high server availability.
Cisco is able to offer the full integration of its core network elements into an umbrella network management system, which provides the overall Operations Support System (OSS)/Base Station System (BSS) infrastructure for the mobile network.
With the introduction of new services such as GPRS and UMTS, mobile networks are becoming multi-vendor environments. For example, there could be several vendors for radio access, a vendor for the GPRS nodes, and another for the IP core. In this environment, the ability to integrate all of the network elements together under a single network management umbrella is important to both simplify provisioning and fault management and control the operations costs of the network.
The Cisco Mobile Exchange framework is provided on the following platforms:
The Cisco 7400 series router is an application-specific router for service providers and enterprises with applications that require a compact stackable form factor, a limited number of interfaces, a high ratio of processing per rack unit, and low power consumption.
Broadband subscriber aggregation is the primary application for the Cisco 7400 series router. The need for broadband aggregation has grown exponentially in the past several years and will continue to grow as subscribers demand more services. The stackability of this product provides the opportunity to "pay as you grow" your customer base in a modular and scalable fashion.
Service selection is another application of the Cisco 7400 series router. Combined with the Subscriber Edge Services Manager (SESM), the Service Selection Gateway (SSG) allows service providers to deploy and deliver value-added services such as videoconferencing, streaming video, business-grade Internet, shopping, and gaming services. Specifically, Cisco SSG and SESM allow service providers to offer and bill for usage-based services. They allow subscribers to dynamically select on-demand services, individually or simultaneously, and they track usage for billing based on connection time for each selected service.
The Cisco 7600 series Internet router delivers optical wide- and metropolitan-area network services with high-touch IP services at the network edge. Service providers and enterprises can provide services at optical speeds, offering competitive advantage and service differentiation to the service provider and high-speed connectivity and link usage efficiency to the enterprise.
The Cisco 7600 series provides a scalable system that offers the ability to bring DS0 to OC-48 WAN connectivity, 10-Mbps Ethernet to 10-Gigabit Ethernet LAN connectivity to the Internet data center, metropolitan aggregation, WAN edge aggregation, and enterprise networking applications. It supports virtual LAN (VLAN) trunking that enables multiple customers in a building or metro area to share the same access switch fabric but use separate VLANs to access the service provider's point-of-presence (POP).
The Multilayer Switch Feature Card (MSFC) in the 7600 chassis provides the performance, scalability, and intelligent services of Cisco IOS® software integrated into the Catalyst series of switches for enterprise backbone and service provider applications. The MSFC supports a full complement of routing protocols to address both enterprise and service provider requirements.
For high-availability, the MSFC also supports Hot Standby Routing Protocol (HSRP) for routing redundancy between MSFCs in the same chassis, across Catalyst switches, or between a Catalyst switch and a standalone Cisco router.
Enterprise and service provider networks require full-featured multilayer switching and services at line-rate speeds. The MSFC delivers hardware-based acceleration for Layer 2, 3, and 4 switching and services with no performance penalty. An example of this is the Cisco IOS policy routing feature. Policy routing is a flexible mechanism in which routing decisions are based on more than just the destination address. For instance, a service provider might enable policy routing to allow certain packets to be routed a different way than the typical shortest-path route.
The MSFC supports traffic statistics-collection and accounting with no impact on switching performance. This data enable enterprise customers to perform traffic engineering, monitor network performance, and provide service provider customers with resource-utilization data for billing and charge-back applications.
The CMX solution uses the policy routing feature and layer 3 static routing of the MSFC to sequentially route traffic through the multiple network elements that provide required functions. Dynamic routing using Open Shortest Path First (OSPF) protocol is used between the GGSN and the MSFC. The routing/switching platform provides layer 2 connectivity for the CMX solution through a 48-port Ethernet blade and supervisor card interfaces. The platform also supports the CMX VLAN functions to separate traffic and layer 2 switching functions.
Catalyst series switches equipped with MSFCs provide transparent Web cache redirection using Cisco Web Cache Communication Protocol (WCCP). The WCCP is a web-cache redirection protocol that localizes network traffic and provides network-intelligent load distribution across multiple network caches for maximized content availability.
The Cisco Mobile Exchange is a framework of solutions that integrates the following elements:
The Service Selection Gateway (SSG) is a switching product for service providers who offer intranet, extranet, Internet, and special content and application connections to subscribers using wireless access technologies. The SSG is an IOS feature that provides multi-service networking and enhanced user experience and billing options. It also provides subscriber authentication, service selection, and service connection capabilities to subscribers.
The SSG communicates with the authentication, authorization, and accounting (AAA) management network where Remote Authentication Dial-In User Service (RADIUS), Dynamic Host Configuration Protocol (DHCP), and Simple Network Management Protocol (SNMP) servers reside. The SSG also communicates with the service provider network, which connects to the Internet, corporate networks, and value-added services.
Together with the SSG, the Subscriber Edge Services Manager (SESM) allows a service provider to create a Web portal that presents subscribers with a menu of services, enabling them to log on to and disconnect from different services using a Web browser. This functionality improves flexibility and convenience for subscribers and enables service providers to bill subscribers for connect time and services used, rather than charging a flat rate.
The SESM operates in RADIUS mode to provide subscriber authentication, authorization, and accounting. This mode obtains subscriber and service information from a RADIUS server. When SSG is used with the SESM, the user opens an HTML browser and accesses the URL of the SESM Web server application. The SESM forwards the user login information to the SSG, which then forwards the information to the AAA server.
In a mobile operator environment, the SSG can also act as a RADIUS proxy for access requests from a downstream network access server (NAS), which shares a RADIUS secret key with the SSG. The Gateway GPRS Support Node (GGSN) can serve as the NAS.
Through the SESM, users can query the status of a session (showing services a subscriber is using), the status of the connection, the current balance for pre-paid services, and system messages from the SSG. This service can also be made free of charge by creating what is called an open garden. An open garden is a collection of websites or networks that subscribers can access as long as they have physical access to the network. Subscribers do not have to provide authentication information before accessing the websites in an open garden. In contrast, a walled garden refers to a collection of websites or networks that subscribers can access after providing minimal authentication information.
Subscribers in GPRS and UMTS networks are logged on to the network in an always-on mode. When no service is in use, the default network area is the open garden.
The user's packet data protocol (PDP) context or point-to-point (PPP) session can be held up so the user is informed before a call is ended. Treating the service connection as a separate entity from the PDP context and PPP session allows the user to be informed of what is happening to the connection.
The SSG separates the service and access technologies. This lets subscribers choose dynamically from a selection of services and lets service providers implement service- and usage-based billing strategies.
In GPRS/UMTS networks, access point names (APNs) must be provisioned in the GGSN, domain naming system (DNS) server, home location register (HLR), and mobile devices. Only a limited number of APNs are supported per mobile handset. If users want to connect to multiple APNs, they must disconnect from the active APN, then establish a connection to a different APN.
The CMX solution to this problem is provided by the Cisco SSG and SESM. The service and access configuration is simple and scalable since only one database (RADIUS server) is provisioned for new services or access. Users can have multiple services active within a single PDP context (i.e., user session) at the same time. This feature enhances the user experience. It also allows the mobile operator to generate revenue using the same radio infrastructure and offer simultaneous services, each billed by a different billing schema. The same is true for CDMA2000 networks, where users can have multiple active services within a single PPP session at the same time.
The SSG allows subscribers to select particular services dynamically. The SSG then switches the subscriber traffic to the selected services. The SSG monitors user connections, service login and logout, and user activity per service. By providing per-connection accounting, the SSG lets service providers bill for connection time and services used rather than charging a flat rate.
The SESM provides an architecture that complies to the Java 2 Enterprise Edition standard. The SESM can be integrated with a service provider's existing Web infrastructure. The SESM is bundled with a Java Runtime Engine (JRE) and the Jetty Web server.
The SSG provides users with access to multiple services simultaneously. These include the Internet, gaming servers, connectivity to corporate networks, and differential service selection. Users can dynamically connect to and disconnect from any of the services available to them.
The Cisco SSG allows users to authenticate their sessions without knowing the URL of the Web portal. If a user, who has not logged in, sends packets upstream to a specified group of TCP ports, the SSG sends those packets to a captive portal group (one or more servers). The Web portal handles the incoming packets by returning a login page to the user.
With the ability to redirect a subscriber to a captive portal, service providers can capture a subscriber's attention with account or service messages (e.g., blocked access to service or payment request). The captive portal Web application on the SESM can also direct a subscriber to services based on interest or location.
The SSG can be configured to work with a single domain naming system (DNS) server (or two servers in a fault tolerant configuration). DNS requests are switched to the secondary server if the primary server fails to respond with a DNS reply within a set time period.
Services offered through the SSG and SESM can be configured for concurrent or sequential access. Concurrent access allows users to log in to one service while simultaneously connecting to other services. Sequential access requires that the user log out of other services before accessing a service configured for sequential access.
The SSG can be configured to allow subscribers, who have already logged on through a point-to-point client, to access the Web portal without requiring them to re-enter their user name and password. This feature is called single sign-on.
The Cisco Content Services Gateway (CSG) is a software and hardware extension for the Cisco Catalyst platforms. The CSG provides a content-metering base that enables applications for network traffic accounting, usage-based network billing, network planning, network monitoring, outbound marketing, and activity tracking. The CSG can retrieve the following content information:
For HTTP requests, for example, the URL of each request is provided. The CSG tracks the user's content transactions in real time and forwards this information to a billing agent for further processing, rating, and invoicing. The CSG measures and delivers the information required for billing based on content.
The CSG provides the following key benefits:
The CSG meters data traffic and generates accounting records. Unlike traditional billing models, which bill for broad classes of traffic, the CSG enables differentiated billing based on the object requested. The detailed accounting records include the user ID, session duration, and bytes uploaded and downloaded. For TCP, the information includes the content transfer size, excluding retransmissions. The connection termination type and initiator are also reported. For HTTP, the URL and hostname of the content request are provided. The billing agent uses this information to apply different rates to different services according to the operator's pricing structure.
The CSG records the URL (up to 512 characters) rather than just the server IP address. The various elements of a URL can have different meanings in a billing context. Domain names determine that a user has accessed a given site. However, directories, filenames, and extensions allow operators to bill for specific types of content such as video streams, MP3 files, and PDF files. Each file type can be billed differently. Individual files of the same type can also be priced differently. Some Web sites might request the user to enter a variable as part of their content selection (for example, entering a destination on an airfare Web site to generate a price). The user might select a series of variables, and the CSG would account for them. The variable is a distinct element in the billing formula. The Universal Resource Indicator (URI) substring, which is what remains beyond the domain name, filename, extension, and variable of the URL, may also be used for billing purposes to provide a premium service or other feature.
The CSG collects the content information and sends it to a billing agent. The billing agent collects all of the information about a data session and formats it for use by the rating and billing engines. The protocols used to communicate with the billing mediation or billing devices are standard and open, enabling the billing agent to receive the CSG records.
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Note The solution described in this document is based on the MIND CTI Real-Time Server (RTS) for AAA and billing mediation functions. Other partners are also available for billing and mediations. |
Service providers can track the type of content being transferred across their networks. The Web sites that subscribers visit create a history of preferences, showing subscriber interests and online purchasing patterns. This information can be used by the service provider to market services that subscribers are likely to pay for. By monitoring subscriber activity on their networks, service providers can modify rating engines to generate additional revenues for high-touch services.
The following configuration limits and performance values apply to the CSG:
The CSG serves two purposes in the CMX framework:
In the first case, the CSG assumes a logical position between the packet gateway and the RLB to register IP traffic. In this position, the CSG provides reference data as a backup to the IP billing provided by the SSGs. If an SSG fails, the CSG sends secondary accounting information of all IP traffic that traversed it to the billing agent. This allows for billing records to be preserved accurately if an SSG fails.
A second CSG is logically positioned between the SSGs and the FWLB. This CSG is positioned to provide content-based billing (layers 4 though 7).
The traffic flows through the CSGs in the CMX framework are described in greater detail in "Data Traffic Flows" section.
Service gateway load balancing is an integral part of the CMX framework. It is key for scalability and switch-over in the event of component failure. Service gateway load balancing is provided by the following elements:
The Cisco IOS-SLB software enables scalable deployment of Service Selection Gateways (SSGs) in a mobile wireless environment. In a GPRS/UMTS network, the RADIUS client is the Gateway GPRS Support Node (GGSN). Because a single GGSN can handle more users than a single SSG, multiple SSGs are required. The SSGs are grouped in a server farm. Each SSG acts as a RADIUS proxy server, inspecting the RADIUS messages that traverse it.
A sample service gateway load balancing configuration is shown in Figure 1-3. Load balancing for service gateways requires that the service gateways be sandwiched between the RLB and the FWLB. To protect against possible load balancer failure, redundant load balancers are deployed.
The RLB and FWLB provide load balancing and fail-over capability for a farm of SSGs. On the subscriber side, the load balancing includes management of the RADIUS message flows, as well as the data traffic. The RLB balances the load of RADIUS messages and data across multiple SSGs in the server farm.
On the network side, load balancing ensures that data traffic for sessions initiated by subscribers is returned to the same service gateway it initially traversed. In addition, the CMX can be configured to load-balance RADIUS messages toward RADIUS (AAA) servers as shown in Figure 1-3.
The RLB, FWLB, and SSG are software functions that reside on hardware platforms. The SSG function resides on the 7400 series platform. The RLB and FWLB functions reside on the 7600 series platform.
The subscriber side requires the RLB data stream sticky feature provided by the IOS-SLB software. This feature examines unique data elements within the RADIUS messages while also acting as a RADIUS load balancer. It caches this information and uses it to balance subsequent connections from the subscriber. Each service gateway is configured as a real server within the SSG server farm. The server farm is configured as a virtual server with a virtual IP address. This virtual IP address is configured in the network address server (NAS) as a RADIUS server. For GPRS wireless networks, this feature examines the content of the RADIUS messages sent to the configured RADIUS virtual IP address, extracts the framed IP attribute, and caches it. This allows the feature to stick all subsequent data flows from that client to the same service gateway.
The RLB detects failure of a real server within the RADIUS server farm by watching for Internet Control Message Protocol (ICMP) errors on the RADIUS flow, as well as using ping health check probes (if they are configured). When one of the entities in the server farm fails, the RLB can reassign new subscriber data flows to one of the other real servers in the server farm or in a backup server farm.
On the network side, the RLB can be configured to load-balance the flow of RADIUS messages toward the RADIUS (AAA) servers for authentication, authorization, and accounting.
The network side must be able to switch return traffic to the same SSG that processed the forward flow. Using the connection-tracking feature of the FWLB, return traffic can be forwarded correctly. The FWLB tracks active connections (defined by protocol, source IP address, source port, destination IP address, and destination port) to ensure that return flows for the same connection are routed to the same service gateway that passed the forward flow.
The load balancing requirements on the two sides of the SSG farm are not symmetric. This asymmetry requires additional logic for application protocols such as file transfer protocol (FTP). By using the source/destination IP sticky feature, these protocols can be properly routed. The load balancer recognizes that the network-initiated connection is related to the pre-existing flow and routes the new connection through the same SSG that handled the original request for service.
Network management of CMX elements comprises a suite of applications for managing mobile wireless service implementations based on different deployment configurations. Network management of CMX elements covers three areas:
The CiscoWorks for Mobile Wireless (CW4MW) software bundle is the element management system used to manage the CMX network elements. The CW4MW discovers the NEs under its domain to build a topology map and discover adjacent NEs. Table 1-1 lists the managment functions provided by the CW4MW.
Table 1-1 CW4MW Management Functions
Additional information on the CW4MW is provided in "CMX Network Management" section.
Figure 1-4 shows an example of the Cisco Mobile Exchange framework in a GPRS/UMTS network.
Posted: Tue Dec 31 04:41:11 PST 2002
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