Guest Comment: WAN IP networks and ‘next generation’ broadcast solutions

Dave Herfert, vice president sales – Americas, Media Links Inc

Broadcasters rely on a diverse array of legacy and newer network technologies to deliver critical video, audio and data signals from venue to destination, writes Dave Herfert, vice president sales – Americas, Media Links Inc. This mix of legacy and current WAN transport methods includes satellite and microwave feeds, SONET and SDH networks, dark fiber, MPLS networks, metro Ethernet, and ATM, DTM, and DWDM transmission systems.

While each of these technologies provides benefits in terms of rate, reach and cost, their continued use leaves broadcasters with a disjointed set of networks that are expensive to operate, hard to provision, and difficult to troubleshoot.

Over the past decade next generation WAN IP networks have emerged as the clear frontrunner among competing transport technologies. Applications for next generation IP networks are numerous and include live sports, live event contribution, stadium-to-studio and studio-to-studio connectivity, remote production and mobile studios.

To increase network revenues with better ROI on hardware investment, efficient use of network bandwidth is essential. Legacy time-division multiplexing (TDM) technologies like SONET allocate bandwidth in discrete channels or bands. But broadcast video and data sometimes don’t fit neatly into these boundaries, so even if trunk or backbone bandwidth is still available, it may not be large enough to fit an uncompressed or moderately compressed video signal. The result: stranded bandwidth on an existing SONET trunk and a new monthly bill for an additional trunk circuit.

Ten Gbps Ethernet links can be provisioned over a variety of transport technologies, including LAN/WAN-PHY, Multiprotocol Label Switching (MPLS), and Dense Wavelength Division Multiplexing (DWDM) networks, so availability is nearly universal.

Priorities and expansion capabilities

Different priority classes can be assigned to video, audio, and data signals traversing the same network path, so that statistical multiplexing gains are achieved. Data circuits can also be provisioned with an upper limit on bandwidth usage; if input bandwidth is exceeded, those data packets are buffered up to a point and then eventually dropped without any effect on video or audio traffic. Finally, Ethernet bit rates, now at 10Gbps, 40Gbps, and 100Gbps, continue to increase, with 400Gbps and Terabit speeds on the horizon.

There is software, hardware or logical limitations on network expansion, but an unlimited number of nodes and circuits can be added to the network, while maintaining edge-to-edge network management visibility. And year-after-year, service providers can continue to ride the downward price curve for IP-based network equipment and circuits.

Media Links’ advanced IP Media Transport solutions use a variety of robust transport delivery mechanisms to ensure that outages never happen or, in those rare cases where they do, that switching occurs seamlessly without signal disruption. At its most fundamental level, power supply, switch fabric and trunk redundancy are built into all Media Links MD8000 equipment.

Spatial Redundancy or Hitless Switching allow users to accept a single input signal and send it as two separate streams across diverse network paths in the network. Both streams arrive at the same destination line card but are typically out of time with each other due to the diverse paths taken. On the destination card, these signals are then realigned and synced with each other to assure precise video timing. Should the primary signal be lost or interrupted, the destination card automatically switches over to the secondary signal without any signal disruption (lossless switching).

In contrast to Hitless Switching, the Auto Protection Switching option monitors the primary channel but does not send traffic on the secondary channel unless the primary channel goes down. This allows for the back-up links to be utilised for best effort transmission; in the event of traffic re-routes the VLAN stream priority ensures categorised ‘7’ traffic (live video) is guaranteed available network bandwidth.

Ensuring network robustness

Another option for improved network resiliency is Forward Error Correction (FEC), a coding technique applied to video/audio frames that can correct a limited number of errored frames on the fly without retransmission. FEC is particularly effective in cases where burst errors occur. Other broadcast specific transport features include QoS monitoring and control of network impairments such as jitter, latency and packet loss.

IP networking delivers seamless end-to-end connectivity from originating Remote Sites/Access networks, to Contribution and Distribution networks, and finally to destination production sites and studios. To ensure reliable 24×7 operations, Media Links provides its customers with a full set of SNMP-based network management tools that give customers the ability to remotely poll, diagnose, troubleshoot and upgrade remote systems in the field, regardless of location. These same network management platforms have been used to manage some of the most highly visible television events in the world, including the Super Bowl, Olympics and World Cup football tournaments.

Since its inception in 1993, Media Links has been committed to video and data over IP broadcast network solutions. Building the company’s products, such as MD8000 access and transport equipment and MDX core switches for this market, demonstrates great technology leadership. WAN IP networking flexibility, converged architecture, and a long list of proven successes mean that Media Links will continue to adapt to new technical challenges and market requirements for many years to come.