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Product Overview
The Cisco® Content Delivery System (CDS) is an integrated system with a network-based architecture that transcends existing video solutions. It incorporates TV streaming for content delivery to digital televisions and set-top boxes (STBs), Internet streaming for content delivery to IP-connected devices, and Cisco Visual Quality Experience (VQE) technology.
The suite of standards-based Cisco VQE applications is designed to deliver the highest video quality of experience (QoE) to consumers. The Cisco CDS is optimized for reliable delivery of broadcast IPTV over lossy access media such as xDSL, but also is useful in optical deployments such as fiber-to-the-x (FTTx).
The system focuses on three applications: Error repair, rapid channel change (RCC), and IPTV statistics reporting.
Error repair effectively mitigates errors associated with IPTV packets as they traverse noisy access circuits. Cisco VQE technology also addresses losses associated with building wiring systems. It uses the Real-Time Transport Protocol (RTP) to provide selective retransmission as defined in RFC 4588, and Application Layer-Forward Error Correction (AL-FEC) as defined by the Society of Motion Picture and Television Engineers standard 2022 (SMPTE 2022) to eliminate visual or audible errors at the receiver.
RCC mitigates several critical delay components responsible for long channel-change times, including Internet Group Management Protocol (IGMP) join latency, Intra Frames (I-Frame) or Instanteous Decoder Refresh (IDR) acquisition time, and STB network-buffer-fill time. Cisco VQE takes advantage of the same RTP technology used for error repair to effectively reduce these and other delay components, resulting in significantly improved channel-change times.
Cisco VQE IPTV statistics enable an innovative, transport-orientated, end-to-end analysis system that represents a major step forward in the operations of the IPTV network. RTP statistics allow service providers to perform a detailed characterization of the video service capability of the network - enabling them to quickly detect, diagnose, and correct any performance problems in the network. At the same time, these statistics enable the characterization of subscriber behavior - information that the service provider can subsequently use to develop new services or deliver addressable advertising. The system offers highly granular Real-Time Control Protocol (RTCP) statistics throughout the network, from video headend devices through the network infrastructure and down to individual client STBs. RTCP XR eXtended Reports compliant with RFC 3611 are also supported, enabling capture of loss Run Length Encoding (loss RLE) from the VQE client, both pre- and post error repair.
Cisco VQE technology consists of server and client components. The VQE server (VQE-S) connects to the Layer 3 multicast edge, which typically resides in the video switching office (VSO). The VQE client (VQE-C) is integrated in the consumer STB; it facilitates error-repair and RCC functions and originates transport-level statistics. The two communicate using standards-based RTCP signaling. The VQE server provides various services to downstream VQE clients such as error repair and RCC. Figure 1 illustrates the relative positioning and communications path of the VQE client and server.
Figure 1. Cisco VQE Server and Client Components
Content-Delivery Applications for Visual Quality Experience
The Cisco CDS is composed of hardware devices called content delivery engines (CDEs), each of which can run one or more content-delivery applications. (Refer to the Cisco Content Delivery Engines data sheet for additional information.)
Table 1 lists the content-delivery applications for visual quality experience.
Table 1. Cisco VQE Applications in the Suite of Cisco Content-Delivery Applications
Product Application
Cisco VQE is designed for service providers offering facilities-based video services over RTP.
Worldwide, service providers connect millions of subscribers to high-speed data (HSD) and voice services over xDSL broadband connections. Video services are being introduced to increase average revenue per user (ARPU) and reduce subscriber turnover. Recent improvements in video-compression algorithms have increased the percentage of broadband connections with sufficient bandwidth for video services. However, video is hypersensitive to packet loss, resulting in visible artifacts and adversely affecting the consumer experience. Although many broadband circuits provide the requisite bandwidth, most do not guarantee the low packet-loss rates required for broadcast-quality video.
Many access lines, such as xDSL, are frequently subjected to electrical impulse noise, resulting in the random corruption of single packets or bursts of packets. Corrupted packets fail integrity checks on customer premises equipment (CPE) and are dropped at the point of entry. Packets may also be subject to the effects of impulse noise as they traverse in-house wiring systems, particularly as households add second or third television sets. Noise problems are also associated with multifamily dwelling units; many have common wiring systems that have grown organically as residents have adopted video services.
Digital Video Broadcasting (DVB), a well-respected organization in the video industry, recommends no more than one artifact per 1-hour movie. Using basic mathematics and applying the recommendation to a standard-definition MPEG-4 service, the resulting packet loss rate (PLR) must be no greater than 7.8 x 10-7. Most service providers accept xDSL bit error rates (BERs) in the range of 10-6 in order to achieve acceptable subscriber coverage. In the worst case, the resulting PLR with this level of loss would be in the range of 1 x 10-3. This loss level would result in a visible artifact every minute - clearly unacceptable to the consumer.
Problems associated with impulse noise create challenges with regard to access circuit qualification. Many service providers are now taking a conservative approach - offering video services only to subscribers connected through known good circuits. The practice often results in service fragmentation where certain households within a given region are ineligible for video service. Service fragmentation presents challenges for marketing campaigns, especially those associated with bundled services.
The Cisco VQE products and technology mitigate the effects of impulse noise in both access circuits and in-house wiring. For example, an MPEG-4 standard-definition service with an average PLR of 1 x 10-3 or an artifact every minute would be transformed into a service with an average PLR of 1 x 10-6 or an artifact every 200 minutes. This PLR would align the service well within DVB's recommendation of one artifact per hour. The system enables video coverage to higher percentages of broadband consumers by lowering the qualification criteria. Increased customer satisfaction improves customer loyalty and elevates service provider brand value.
Rapid Channel Change and IPTV
IPTV possesses various network-related factors that contribute to overall channel-change time. These factors include I-Frame or IDR acquisition time, STB network-buffer-fill time, IGMP leave or join time, and MPEG table acquisition time among others. These factors can vary significantly depending on network topology, available bandwidth, content encoding parameters, and whether or not AL-FEC is enabled. Depending on the installation, the effect on channel-change time can vary from hundreds of milliseconds to several seconds and beyond. For example, use of AL-FEC error protection with a large protection block will significantly increase the STB network-buffer-fill time and can contribute hundreds of milliseconds to the channel-change performance. Similarly, content encoding with long Group of Pictures (GOP) periods will directly increase the I-Frame or IDR delay factor and variability.
The Cisco VQE technology mitigates the effects of these channel-change factors by using capabilities of the VQE client and VQE server together. The STB channel-change request initiates control messaging between the VQE client and VQE server, resulting in a video decoder "priming" packet being sent to the VQE client to expedite the initial I-Frame and other video initialization at the decoder. This packet is immediately followed by a RTP unicast transmission of video content from the VQE server cache for the target channel. Simultaneously, the VQE client initiates an IGMP join to the target channel. The VQE solution then carefully manages a transparent hand-off from the unicast to the multicast stream, completing the RCC operation while dramatically improving channel-change performance. The solution addresses both timing and variation attributes of channel change.
Features and Benefits
Table 2 lists Cisco VQE application features and benefits.
Table 2. Features and Benefits of Cisco VQE
Product Architecture
The Cisco VQE system is ideal for deployment at the edge of the service provider's network, but it can be deployed as a centralized system. The system consists of server- and client-side components. Typically, Cisco CDE 110 and CDE 111 engines running the Cisco VQE application are directly connected to the multicast Layer 3 edge device, such as a Cisco 7600 Series Router. The client consists of a lightweight software component, which is integrated in a STB or potentially other suitable customer premises device such as the home access gateway (refer to Figure 2).
Figure 2. High-Level Network Diagram
Primary Functions of the Cisco VQE Application
Join and Cache Video Content
Service providers use multicast groups to transport linear TV channels across the network infrastructure from video headend to provider edge. Cisco VQE joins multicast groups using the industry-standard IGMP. The Cisco VQE application caches 1 to several seconds of content for each channel in high-speed DRAM. Content continuously ages out and is refreshed. Cached content provides VQE services such as error repair and RCC to downstream VQE clients.
NAT Support
The Cisco VQE application supports an embedded serial tunnel (STUN) server to facilitate all Cisco VQE client Network Address Translation (NAT) mapping types, including symmetric NAT per RFC 4787. VQE clients exchange messaging with the VQE application STUN server to resolve NAT mapping parameters. Universal Plug and Play (UPnP) NAT transversal support has been added.
RTP and RTCP
The Cisco VQE application listens for inbound RTCP messages from downstream VQE clients. Messages request specific VQE services such as error repair or RCC, or they present RTP receiver statistics. To service client requests, the Cisco VQE application responds to the originating client with appropriate action. It responds to NACKs with missing video packets. RCC requests results in an acknowledgement packet, followed by video priming data and unicast RCC transmission bursts on the selected channel. Inbound RTP receiver statistics are periodically exported, using TCP, to an appropriate database and video quality analysis application.
Primary Functions of the Cisco VQE Client
Packet Reordering and Jitter Elimination
The Cisco VQE client, integrated with a STB, monitors RTP sequence numbers of inbound IPTV packets in its network buffer. As a fully compliant RFC 3550 RTP receiver, the client resequences out-of-order packets and mitigates the effects of network-induced jitter before forwarding packets to the STB MPEG demultiplexer stage.
Forward Error Correction
The Cisco VQE client receives standards-based FEC repair packets and searches for missing RTP sequence numbers encountered across a FEC-protected block period of N packets. FEC protection periods are determined at the headend by definition of the FEC block size in terms of L columns by D rows of packets. The VQE client automatically corrects missing RTP packets within the FEC block coverage by using received FEC protection packets. Any missing RTP packets beyond FEC coverage are forwarded to the selective retransmission function.
Error Repair: Selective Retransmission
The Cisco VQE client waits for missing RTP sequence numbers. If packets have been dropped and remain uncorrected following FEC repair, the client requests retransmission of the packets from its designated VQE server. Retransmitted packets are resequenced and dejittered in the client network buffer prior to MPEG demultiplexer handoff. A single RCTP message may request retransmission of multiple contiguous or noncontiguous packets.
Rapid Channel Change
The Cisco VQE client notifies the designated VQE server of a channel-change request from the viewer. The VQE server responds with a positive or negative acknowledgement. If negative, the VQE client conducts a standard channel-change procedure and does not employ acceleration techniques. If positive, the VQE client engages with the VQE server to conduct a RCC procedure. Video decoder priming information is delivered next, followed by RTP unicast transmission for the target channel. The STB decoder begins video playout soon after initial video packets arrive, resulting in greatly improved channel-change time. Simultaneously, the VQE client performs IGMP leave or join and STB network-buffer-fill operations, concluding the RCC procedure with a transfer to the target channel multicast RTP stream.
RTP Receiver Reports
Clients transmit RTCP receiver reports to their designated VQE server. Reports provide cumulative counts of lost and received packets as well as packet latency and jitter; per-channel statistics are provided. Network operators may set the frequency of periodic reports using the Cisco VQE Channel Provisioning Tool.
Monitoring and Channel Provisioning
Monitoring
The Cisco VQE application incorporates an integrated web server, enabling network operators to access application health and per-channel summary statistics. They can use any standard web browser that supports HTTPS to access this information. Figure 3 displays a top-level view of the Cisco VQE application in terms of health status.
Figure 3. Cisco VQE Application Health Monitoring
The Cisco VQE monitoring interface may be used to provide basic channel lineup information. Specifically, it provides network-level information: ingest health and a snapshot of active VQE clients associated with each channel. Figure 4 shows an example of this view.
Figure 4. Cisco VQE Application Channel Lineup Information
Channel Provisioning
The Cisco VQE Channel Provisioning Tool (VCPT) provides a middleware-independent application to define and associate channel network information with VQE servers and clients. The highly intuitive graphical interface uses a template-based approach to simplify channel and server configuration. The application offers a powerful clone facility to help expedite channel definitions.
Cisco VCPT is designed to run on a dedicated Cisco CDE 110 or CDE 111. It uses industry-standard signaling and protocols to communicate with associated VQE servers and clients. The system transmits channel network information to servers using the industry-standard Session Description Protocol (SDP). Figure 5 shows the relationship between Cisco VCPT and other VQE network components.
Figure 5. Cisco VQE Channel Lineup Information
Cisco VCPT provides four primary functions:
• Definition and configuration of channel lineups, specifically network-related information
• Definition and identification of VQE servers, specifically network addresses
• Association of channel lineups with groups of servers
• Option to save configuration files and push configuration files to appropriate VQE servers
Figure 6 displays a channel lineup summary from the Cisco VCPT application.
Figure 6. Cisco VCPT Channel Summary Information [[place at top of figure]]
Product Specifications
Table 3 lists the specifications for the Cisco VQE application.
Table 3. Specifications for Cisco VQE Application
System Requirements
The Cisco VQE application and Cisco VQE Channel Provision Tool are designed to run on separate dedicated Cisco CDE 110 and CDE 111 servers. Please refer to the Cisco Content Delivery Engine data sheet for technical details of these appliances.
Table 4 summarizes performance information of the Cisco CDE 110 and CDE 111 with the Cisco VQE application.
Table 4. Scale and Performance Summary: Cisco CDE 110 and CDE 111 with Cisco VQE Application
Ordering Information
To place an order, visit the Cisco Ordering Home Page at: http://www.cisco.com/en/US/ordering/index.shtml and refer to Table 5. To download software, visit the Cisco Software Center at: http://www.cisco.com/public/sw-center/index.shtml.
These should be standard URLS:
Table 5. Ordering Information
Please contact Cisco for technical details, location, and availability of Cisco VQE open-source client software.
Service and Support
Using the Cisco Lifecycle Services approach, Cisco and our partners provide a broad portfolio of end-to-end services and support that can help increase the business value of your network and your return on investment. This approach defines the minimum set of activities needed, by technology and by network complexity, to help you successfully deploy and operate Cisco technologies and optimize their performance throughout the lifecycle of your network.
For More Information
For more information about the Cisco Content Delivery System or Cisco Content Delivery Engines, contact your local Cisco account representative or visit:
http://www.cisco.com/en/US/products/ps7191/Products_Sub_Category_Home.html.
http://www.cisco.com/en/US/products/ps7191/Products_Sub_Category_Home.html.
The Cisco Content Delivery Engine data sheet is available at:
http://www.cisco.com/en/US/products/ps7126/index.html.
http://www.cisco.com/en/US/products/ps7126/index.html.
The Delivering Video Quality in your IPTV Deployment white paper is available at: http://www.cisco.com/en/US/netsol/ns610/networking_solutions_white_paper0900aecd8057f290.shtml.