| In addition to the on-demand caching and live stream splitting that you learned about in Chapter 13, "Delivering Cached and Streaming Media," an ACNS network can allow you to enable the following rich multimedia features on your network: Pre-Positioned On-Demand Channels ACNS provides you the ability to distribute objects within the network in advance of client requests. You learned previously how CEs populate themselves on-demand by caching copies of content inline with clients' requests. With ACNS, you can pre-position streaming or nonstreaming channels of organized static files, such as HTML, Macromedia Flash, Shockwave, JPEG, Windows Media, Apple QuickTime, and RealNetworks, to CEs in advance of client requests during off-peak hours. Scheduled Live or Rebroadcasted Channels ACNS provides integration with the Cisco IP/TV streaming media solution and third-party streaming server software, such as Windows Media Technologies (WMT), RealNetworks, and Apple QuickTime, for scheduled live or rebroadcast events.
The ACNS system comprises the following elements: Content Distribution Manager (CDM) The CDM is the heart of the ACNS network solution. The CDM is the central management console of an ACNS network and is responsible for facilitating the pre-positioning of on-demand content and for scheduling live streaming programs. The CDM does not directly store any of the content locally. Alternately, for on-demand content the CDM uses manifest files, which are XML files that you can write to instruct the CEs on the following: the origin servers that the content resides on and what content on the origin servers should be distributed in the ACNS network. For live or scheduled rebroadcast content, the CDM schedules programs and organizes the distribution of the streaming content to your users. CEs If the CDM is the heart, then CEs are the limbs of the ACNS network. They do the work in distributing files and providing caching and streaming services to requesting clients. As you learned in Chapter 13, through third-party licensing, the CE can run both WMT and RealNetworks proxies for splitting and caching of streaming content. However, this feature is unique to the ACNS systemyou can serve streaming content directly from both Windows Media Server (WMS) and RealNetworks server software that you can license and enable on your CEs. Additionally, with ACNS, you can enable the Cisco Streaming Engine. The streaming engine is a standard Real-Time Streaming Protocol (RTSP) server and can be used to proxy and directly stream Motion Picture Experts Group (MPEG)1/2/4 and Apple QuickTime streaming content. The Cisco Streaming Engine does not require a separate third-party license. Content Routers (CR) The Cisco Content Router is the nose of the ACNS network, used to sniff for the best location of the content to serve to clients. CRs use Domain Name Server (DNS) and HTTP/RTSP redirection for routing client's content requests. As with the Global Server Load Balancing (GSLB) devices that you learned about in Chapter 12, "Exploring Global Server Load Balancing," the subdomains that the CR responds to must be delegated to the CR by the DNS servers that are responsible for the domain. To source your own MPEG1/2/4 or Apple QuickTime live or VoD streams, you can use Cisco IP/ TV streaming solution, instead of using a third-party solution. You can use the Cisco IP/TV system either on its own or within an ACNS system. Used with the ACNS system, you can distribute and route IP/TV content much more efficiently than as a stand-alone system. The Cisco IP/TV 3400 series video server solution consists of the following elements: IP/TV Program Manager To schedule live IP/TV streams, you must use the IP/TV Program Manager. The IP/TV Program Manager software runs on the Cisco CE hardware in separate device modes that you can configure via the CE command-line interface (CLI). IP/TV Broadcast servers To source live streams, you must use the IP/TV broadcast server. This server is capable of encoding and delivering MPEG1/2/4 and Apple QuickTime live streams for live or on-demand delivery. The IP/TV broadcast server requires a dedicated Cisco-branded IP/TV hardened appliance or a generic standalone server. You acquire this appliance or server yourself and install the broadcast server IP/TV software on it. If you use your own hardware, make sure that your capture cards are supported by the IP/TV Broadcast software first. IP/TV Viewer To view content that is created with the IP/TV Broadcast server, you can use the Cisco IP/TV viewer.
Figure 14-1 illustrates a typical ACNS network topology that will be used throughout illustrations and examples in this Chapter. Figure 14-1. A Content Distribution and Routing Topology 
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