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Solving Video-Related Network DelaysBy Drew RobbDecember 27, 2010
Adding to the load, video surveillance is now commonplace and video is increasingly being included on product and news pages. Consequently, many more networked video devices are coming onto the IP network. "There is a significant market transition under way as organizations prepare for pervasive video use,” said Marthin De Beer, senior vice president of the emerging technologies business group at Cisco systems. “This transition is even more profound than the transition to e-business in the 1990s.” As the business world has adopted this technology more widely, it has given rise to the introduction of medianets to deal with such traffic. The challenge, though, is to deliver these applications with the desired level of quality and interoperability. These medianets are aware of the network, the various media involved and the endpoints being connected; the network boundary is extended to include the endpoints as a means of enhancing video performance. “Video is quickly becoming as important to the enterprise as e-business was 15 years ago,” said De Beer. “We are making investments across our medianet video architecture to make it more accessible and easier to scale, delivering the best user experience possible." A medianet, then, is a network with built-in intelligence that delivers multimedia to any device on the network. The aim is to reduce the cost and complexity of video deployments and more efficiently utilize network resources to provide the best video quality while also automating configuration. A medianet detects traffic conditions and ensures proper transmission of the various streams. In addition, it can recognize the different types of media being transmitted, verifying that they are created, sent, and delivered properly. This enables staff to view a video stream from a surveillance camera, for instance, on a mobile device by adapting the resolution and format so that it best fits the available speed of the wireless connection. Cisco, for example, has added various medianet technologies, which are services added to routers, switches, and rich-media endpoints. Known as Cisco Networking Capabilities for Medianet, this creates tighter integration between network services and the media. The Media Services Interface (MSI) is a piece of software that is loaded on endpoints. This creates a much more responsive network infrastructure. The old methodology of prioritization of traffic – video then audio then text – is ill-suited to cope with the rise of video. Instead, all streams have to be handled within the same stream to maintain Quality of Service (QoS) guarantees. While this may take care of the networking side, holes remain when it comes to traffic management. “Video applications are sensitive to fluctuations in network performance,” said Aamer Akther of Cisco. “After the video has been packetized for IP transport, the network’s contribution to the video stream’s performance is generally limited to delay, jitter, and loss.” Those involved in a video conference, for instance, don’t spot minor delays in transport. But once this gets above about 400 milliseconds, they start to notice it. This Quality of Service (QoS) unpredictability shows up in voice over IP (VoIP) as well as video over IP. As a result, traditional network management tools are struggling to cope and this is showing up in poor quality across a growing range of network applications. Packet analyzers are one solution to the management and troubleshooting of network video and voice applications. Also known as protocol analyzers, packet sniffers or probes, they harness software or hardware to capture each packet, decode it and analyze it. However, due to cost, they are typically used only at key locations or installed on a temporary basis after an anomaly has been detected by other monitoring software.
Flow MonitoringThrowing additional bandwidth at the issue is another expensive way forward. Yet it often isn’t necessary. By achieving greater insight into the network, it is possible to understand the media stream and its requirements. This can be accomplished using flow monitoring. This is a push technology activated on the switch or router to provide data on packets to a collector, which is a server set up with a database and analysis software to convert that raw flow data into charts, graphs and reports for instantaneous use.There are two varieties of flow monitoring: sFlow and NetFlow. The former is a hardware-based technology developed by Inmon Corporation and consists of a chip installed in a network device. The alternative approach is NetFlow, which was developed by Cisco and is part of the company’s Internetwork Operating System (IOS). A standard called IPFIX makes NetFlow useable on non-Cisco networking devices. With NetFlow activated on a router port, for instance, it is possible to see where that traffic was coming from and what they were sending. This is particularly important when checking the network for a media stream’s loss, latency, and jitter. “NetFlow is a technology that monitors and records all IP traffic passing through the supported router or switch,” said Michael Patterson, CEO of network monitoring firm Plixer “Prior to this technology, IT administrators could see how much traffic was on a network, but they couldn’t see what kind of traffic it was.” NetFlow collectors gather data to present trending and measurement data concerning network traffic. Plixer, for example, offers the Scrutinizer NetFlow Analyzer, which reports on the new metrics Cisco embedded into NetFlow that are designed to operate on medianet. Its Medianet Performance Monitoring Reports provide data on traffic related to voice and video. To configure NetFlow exports of Cisco’s Performance Monitoring, routers need to be running Cisco IOS version 15.1. “Through the use of NetFlow analysis and medianet’s stream-aware architecture, there is much greater insight into troubleshooting VoIP connections,” said Patterson.
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