Hierarchical multicast caching

Multicast is an efficient way of sending data to multiple receivers simultaneously. To support mobility, multicast caching has been introduced as a method for allowing roaming clients to request packets that they have been unable to receive during the change from one access network to another. The basic idea has been to introduce a multicast cache, which stores the multicast streams as individual, uniquely defined, packets. The mobile clients may upon entering an access network request the packets that they lack from the multicast cache. The main problem with the current approach is that a multicast cache that does not contain the requested packets merely returns an error message to the mobile client. To solve this problem, we extend the model to allow multicast caches to forward client requests according to some dynamically configurable policy. If another multicast cache contains the data, it is sent it to the client, which then can continue processing the multicast stream as it normally would.