Enterprise Briefing

primer

IP Multicasting

The increasing use of rich media content is leading many enterprises to investigate IP multicasting. Enterprise Briefing looks at how multicasting can reduce the overall network load, and deliver video and other content more efficiently.

what is IP multicasting?

IP multicasting is a way of distributing the same information over a network to multiple users without having to send it to them individually. The opposite is unicast, which requires a dedicated end-to-end transmission for each user. Because multicasting allows users to share the same information over part of the network, the entire infrastructure can be used more efficiently. The technology has been around since the mid-1980s and recently has been used by broadcasters and service providers to distribute television signals over IP networks. Now multicasting is becoming much more widely used in the corporate network as more businesses adopt media-rich content.

can any sort of content be multicast over the enterprise network?

Any content that needs to be sent to multiple users can be multicast. The higher the bandwidth requirement and the more users, the greater benefit enterprises can gain from multicasting. The increasing use of video within enterprises has been one of the main drivers for multicasting. Typical enterprise applications, such as video podcasting or streaming, video surveillance and e-learning are very well suited to this approach. But its not just video. Many organizations will need to distribute music-on-hold stored centrally around their organization, or even send data streams to multiple users, such as software patches or anti-virus updates.

how does multicasting work?

A single transmission is sent from the source across the network, then it is replicated at the edge router and again before it reaches the user so that everyone eventually gets their own copy. For example, if a video podcast is requested by multiple users in different sites, a single copy of the transmission is sent to each site, where it will be replicated again for the users. Or perhaps the podcast is located in the US, whereas the sites requesting it are in Europe; multicasting means it is only sent once across the Atlantic. Enterprises are able to control their network traffic more effectively and reduce server loads. Multicasting will also improve the performance of the application and avoid any contention issues, particularly at the source of the transmission.

are there any special considerations for multicasting?

Unlike unicast transmission, which uses the TCP protocol, multicasting uses the UDP protocol. Put simply, this means that multicasting uses best-effort delivery and dropped packets are not resent. In practice, this makes little difference to video or audio transmissions, but companies wanting to use multicasting for data transmission such as software patches will need to put another level of control in place.

does Orange's multicasting service require any additional equipment?

Multicasting requires no additional dedicated customer equipment and is delivered as a fully-managed service by Orange. The service is available worldwide with a number of different access methods, including SDSL, Ethernet and leased line. Multicasting traffic is carried over Orange's IP VPN network, which means that it conforms to the customer's existing classes of service. Enterprises looking to deploy multicasting will need to analyze their network in advance to see how it will affect their existing unicast traffic, and whether the line quality is good enough in all locations. Because multicasting is typically deployed to support increased use of video, it is possible that some locations will require additional network bandwidth.