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Multicast Rising

Multicast hasn’t been a hot topic in networking in recent years, but that may be changing with last week’s announcements by both AT&T and Verizon that they will launch LTE multicast in 2015. Verizon plans to start embedding the technology in phones in the fourth quarter of this year and commercially launch the service in 2015. AT&T will also begin to roll out multicast capabilities next year.

According to Verizon CFO Fran Shammo, multicast is “…the pivotal point that starts to change the way content is delivered over a mobile handset which opens up content into the wireless world.” 

As Humberto Saabedra explains in an article for “LTE Multicast allows the same content to be sent to a large number of subscribers at the same time, resulting in a more efficient use of network resources than each user requesting the same content and then having the content individually streamed to each user.” 

Currently, organizations use multicast for multimedia distribution, desktop imaging, market trading data distribution, broadcast video, online education, and other purposes where data must be delivered simultaneously to multiple receivers. Packet Designed has been offering multicast management for these uses since last October. One of our first customers is a large school district that supports 20,000 wired and wireless clients across more than 60 facilities and five core sites. 

The school district’s network group started using multicast in 2000 for video broadcasts using the free Windows Media server. This offered very basic services and the network team had to encode videos for the teachers and administrators. As a result, it remained a little-used protocol. 

The school district invested in a new multicast-based application for the following uses:

  • Desktop imaging (Windows imaging server): During each multicast session, other machines can join in anytime and start receiving. The broadcast starts over so that they can complete the download.
  • Video streaming: The new system puts video manipulation in the hands of the end user. Teachers can encode their own videos and put them on the server, which facilitates more use of the medium.
  • IPTV: The school district has six cable channels (for educational programming, news, weather, etc.) that they are redeploying across the network using multicast. This is a migration away from CATV and VHS tapes.
  • Digital signage: Each campus can have as much signage as they want. They can broadcast emergency notices, morning announcements, campus news and events, etc.

From a management standpoint, the network team needed help troubleshooting the new system. Lacking multicast expertise, they often did not know where to begin looking for the source of problems. It is difficult and tedious to use the CLI to look at every switch and router, especially when you don’t know where to begin.

The challenge is understandable, since multicast management is complex. This quick excerpt from our white paper on “Understanding and Managing Multicast Routing outlines part of the problem: 

“In unicast, IP addresses are often associated with specific assets such as desktops, laptops, phones, tablets and printers. Unfortunately, this visibility is lost with multicast addresses. Ideally, multicast addresses should be allocated by the network operator, but in reality, many network operators do not know what multicast addresses are used in the network and what they are used for. This is because applications can randomly pick a multicast address and start using it. One network operator for a financial company estimates there are sixteen thousand multicast groups in his network and aims to reduce it to less than four thousand groups. This requires visibility into existing multicast groups in the network, as well as the sources, the receivers and the trees for each.” 

The school district’s network group invested in Multicast Explorer, a module of the Route Explorer System, to better manage their multicast services. While other tools rely solely on CLI commands and SNMP polling to collect multicast configuration data, Route Explorer plugs directly into the Layer 3 network as a passive participant in the routing topology. This enables it to capture changes as they occur and provide visibility into multicast trees, groups and events graphically in the context of the whole network. With real-time views and the ability to use a DVR-like capability to replay multicast routing events at a given point in time, the networking group can troubleshoot problems more quickly by pinpointing where problems are and discovering anomalies. They can also model what/if scenarios to see how changes will impact their network. Overall, they expect Multicast Explorer to help them improve the delivery of their critical multicast services. 

Be sure to download the white paper for more information about the challenges of running multicast applications:

Editorial Staff

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