Scenario: Multicast support for a CDN

About this scenario

This scenario describes a deployment in which NetCache appliances owned by a CDN are configured for multicast input. The CDN in this scenario provides services for several ISPs.

Organization's requirements

The organization's requirements are as follows:

Minimize internal bandwidth use in the CDN data center by using multicast
Manage multicast streaming requests based on preconfigured priorities
Log streaming activity by each ISP

Deployment illustrated

The following illustration shows the traffic flow from the streaming server after it receives a multicast stream request.

The benefits of using NetCache multicast support are described in the following paragraphs.

If the router between the content provider data center and the POPs is a unicast router

In this scenario, the router at the POP is a unicast router. Configuring the NetCache appliances for multicast input (and using the default of unicast out) has the following benefits:

A unicast router cannot route multicast transmissions. Configuring NetCache appliances for multicast input enables the appliances to listen for multicast transmissions from the multicast-enabled routers in the data center. The NetCache appliances can then convert the multicast transmissions to unicast for routing to the unicast router at the POP.
Forcing all multicast streams to be sent through the NetCache appliances enables the CDN to take advantage of NetCache services that will help achieve the CDN's other goals. For example:
- NetCache can log streaming activity. The ContentReporter reporting application can be used to consolidate logs from each NetCache appliance and report that data in report formats that the CDN requires. The CDN might want data for billing each ISP for services.
- If the NetCache bandwidth management feature is configured, NetCache can manage bandwidth based on the configured priorities.

If the router between the content provider data center and the POPs is multicast-enabled

It would not be necessary to route streams through multicast-enabled NetCache appliances to achieve the CDN's goal to minimize bandwidth consumption. However, forcing all multicast streams to be sent through the NetCache appliances enables the CDN to take advantage of NetCache logging and bandwidth management features, as previously described.

Most ISPs cannot accept multicast transmissions from the Internet. If the ISPs for which a CDN provides services can accept multicast transmissions, for example, because a satellite link exists between the CDN and the ISP, the CDN could configure its NetCache appliances in the data center for multicast output. The CDN would then need to advise administrators of the ISPs to configure their NetCache appliances for multicast input.