Scenario: Deploying multicast in an enterprise

About this scenario

This scenario describes a multicast-enabled NetCache appliance deployed in an enterprise that is multicast enabled.

Organization's requirements

The organization's requirements are as follows:

Reduce bandwidth consumption on the network
Protect the routers from traffic overload
Streams from origin servers on the Internet are to be distributed on the company's multicast-enabled network using multicast transmission

Deployment illustrated

The following illustration shows a deployment in which a NetCache appliance configured for multicast output was deployed at the Internet access point.

Use of a NetCache appliance configured for multicast versus a multicast-enabled router

The NetCache appliance in the previous illustration is configured to convert the unicast stream from the Internet to multicast (multicast out) for distribution on the company network. A multicast-enabled router could have been deployed at the Internet access point. However, the advantages of deploying a NetCache appliance at the Internet access point are as follows:

NetCache sends only one request for the same unique live stream to the origin server, no matter how many clients request that stream. A router would send each client's streaming request individually to the origin server.
NetCache provides a number of features that are not available with a router, for example, logging and access controls.
Most streams from the Internet are not multicast. If a multicast-enabled router was used, source streams would have to be multicast because a multicast router cannot convert unicast transmissions to multicast.

Client-to-server traffic in the illustration

The NetCache appliance sends only one request for the same unique stream to the origin server, no matter how many clients request that stream. This behavior accomplishes the company's goals to conserve bandwidth. Additionally, the border router is protected from traffic overload because only one request is sent through the border router on the way to the origin server. A separate request for each client would be sent through the border router if the NetCache appliance was not deployed inside the border router.

Server-to-client traffic in the illustration

The origin server responds with only one copy of the requested unique stream (because it received only one request from the NetCache appliance), thereby reducing bandwidth usage. The NetCache appliance, which is configured for multicast output, passes the stream to the multicast channel instead of splitting it. Each multicast router in the routing path determines whether to pass the stream through to the next branch of routers or split the stream. The use of multicast, therefore, protects the routers on the company's network from traffic overload. Clients configured for multicast listen for multicast traffic. Only one copy of the data is passed to the network of multicast-enabled clients.