Method for providing a content part of a multimedia content to a client terminal, corresponding cache

1. A method for providing a content part of a multimedia content to a client terminal, one or more caches being arranged along the transmission path between the client terminal and a remote server, several representations of said content part being available, comprising:

receiving at a first cache, from the client terminal, a request for a given representation of said content part, belonging to a set of allowable representations selected among said available representations, said request further comprising a list of alternative representations of the set and an auxiliary directive for specifying a number of remaining caches arranged between the client and the server which are allowed to forward said request to a next cache, in case said given representation and said alternative representations are not stored;

checking at said first cache if said given representation is stored in the cache;

in case said given representation is not cached, browsing at said first cache alternative representations listed.

2. The method according to claim 1 , wherein an error message is sent to the client when the last cache of the remaining caches is devoid of said given representation and said alternative representations.

3. The method according to claim 1 , wherein the auxiliary directive defines a final cache arranged along the transmission path, so that the request is not forwarded by said final cache, in case said given representation and said alternative representations are not stored in the latter.

4. The method according to claim 3 , wherein an error message is sent to the client when said final cache is devoid of said given representation and said alternative representations.

5. The method according to claim 1 , wherein the alternative representations are browsed in order of preference.

6. The method according to claim 1 , wherein each alternative representation has a corresponding bitrate lower than the one of the given representation.

7. The method according to claim 6 , wherein each allowable representation of the set has a corresponding bitrate at most equal to the bandwidth of the transmission path between the client terminal and the remote server.

8. The method according to claim 1 , wherein, the transmission protocol used being HTTP, the request is an HTTP request and the Cache Control extension of said HTTP request comprises said list of alternative representations.

9. The method according to claim 1 , wherein said request comprises additional information, such that the first cache returns the requested representation or a listed alternative representation, if cached, or a response message in case neither the given representation nor any of the listed alternative representations is cached.

10. The method according to claim 9 , wherein, when the transmission protocol used is HTTP, said additional information is included within the cache control extension of said HTTP request.

11. A cache configured for providing a content part of a multimedia content to a client terminal, said cache being arranged along the transmission path between the client terminal and a remote server, several representations of said content part being available, comprising:

an interface module for receiving, from the client terminal, a request for a given representation of said content part belonging to a set of allowable representations selected among said available representations, said request further comprising a list of alternative representations of the set and an auxiliary directive for specifying a number of remaining caches arranged between the client and the server which are allowed to forward said request to a next cache, in case said given representation and said alternative representations are not stored;

a controlling module for checking if said given representation is stored;

a browsing module formed to browse alternative representations listed, in case said given representation is not cached.

12. The cache according to claim 11 , wherein the alternative representations are browsed in order of preference.

13. The cache according to claim 11 , wherein, an auxiliary directive defining a final cache arranged along the transmission path, the request is not forwarded in case:

said given representation and said alternative representations are not stored in said cache; and

said cache corresponds to the final cache.

14. A cache for providing a content part of a multimedia content to a client terminal, said cache being arranged along the transmission path between the client terminal and a remote server, several representations of said content part being available, comprising:

at least one memory; and

one or more processor configured to:

receive at a first cache, from the client terminal, a request for a given representation of said content part, belonging to a set of allowable representations selected among said available representations, said request further comprising a list of alternative representations of the set and an auxiliary directive for specifying a number of remaining caches arranged between the client and the server which are allowed to forward said request to a next cache, in case said given representation and said alternative representations are not stored;

check at said first cache if said given representation is stored in the cache;

in case said given representation is not cached, browse at said first cache alternative representations listed.