The invention concerns a device for reserving bandwidth for an adaptive streaming client belonging to at least one network and configured for receiving a streaming content from at least one server, the streaming content being available at more than one data rate at the server, said device comprising: a stream identifier (12) configured for detecting at least one streaming content requested by said client; a bandwidth manager (13) configured for temporarily reserving for the client, when at least one event occurs, a transient bandwidth depending on the predetermined target data rate associated with the requested streaming content and a transient margin.