A method, for requesting to transmit multicast data, wherein, said method comprises: generating, by an Any Source Multicast ASM-based multicast source, a multicasting multicast transmission request which indicates a multicast address, representing that the multicast source requests to transmit multicast data to the multicast address, wherein a multicast packet is generated as the multicast transmission request with destination address being the multicast address; transmitting, by the multicast source, the multicast packet to an Any Source Multicast ASM-based forwarding device designated for a multicast group to which the multicast address belongs; transmitting, by the forwarding device, the multicasting multicast transmission request to a Rendezvous Point RP corresponding to the multicast address, wherein the forwarding device queries pre-stored mapping information to find the RP corresponding to the multicast address, generates a new unicasting multicast transmission request whose destination address is the IP address of the RP and writes the multicast address into a specific field whose position and function is known to the RP, wherein the multicast transmission request indicates the required bandwidth corresponding to the multicast address or wherein the RP estimates the bandwidth that will be occupied by the multicast transmission; receiving, at the ASM-based multicast source, a multicast request response from the RP, the multicast request response indicating whether the multicast source can transmit multicast data to said multicast address, the response generated based on said multicast transmission request and remaining multicast forwarding resources in said RP. generating, by an Any Source Multicast ASM-based multicast source, a multicasting multicast transmission request which indicates a multicast address, representing that the multicast source requests to transmit multicast data to the multicast address, wherein a multicast packet is generated as the multicast transmission request with destination address being the multicast address; transmitting, by the multicast source, the multicast packet to an Any Source Multicast ASM-based forwarding device designated for a multicast group to which the multicast address belongs; transmitting, by the forwarding device, the multicasting multicast transmission request to a Rendezvous Point RP corresponding to the multicast address, wherein the forwarding device queries pre-stored mapping information to find the RP corresponding to the multicast address, generates a new unicasting multicast transmission request whose destination address is the IP address of the RP and writes the multicast address into a specific field whose position and function is known to the RP, wherein the multicast transmission request indicates the required bandwidth corresponding to the multicast address or wherein the RP estimates the bandwidth that will be occupied by the multicast transmission; receiving, at the ASM-based multicast source, a multicast request response from the RP, the multicast request response indicating whether the multicast source can transmit multicast data to said multicast address, the response generated based on said multicast transmission request and remaining multicast forwarding resources in said RP.