A first device configured to communicate with a second device in a network, the first device comprising: a processor configured to register a second device, using multiple registration modes, with respect to the first device, including a domain-registration mode, a device-registration mode, and a no-registration mode, wherein the domain-registration mode allows the second device to register with the first device and at least one other device registered with the first device, said at least one other device being in the domain of the first device, the device-registration mode allows the second device to register with the first device and with no other devices, and the no-registration mode does not allow any device to register with the first device, wherein the processor is further configured to receive a selection of one of the multiple registration modes and place the first device in the selected registration mode, and wherein the processor is further configured to receive a registration request message from the second device, the registration request message identifying one of multiple registration modes, with respect to the second device, including at least a device-only mode and a source-domain mode; a data storage storing a registration key used to register the second device with the first device; and a network interface configured to exchange messages with the second device for registration depending on the selected registration mode via a network, if the registration mode with the first device is set to the domain-registration mode, the processor is further configured to identify a registration mode with respect to the second device upon receipt of the registration request message from the second device, if the identified registration mode with respect to the second device is the device-only mode, the processor is further configured to allow the second device to register only with the first device, and if the identified registration mode with respect to the second device is the source-domain mode, the processor is further configured to allow the second device to register with not only the first device but also said at least one other device in the domain of the first device. a processor configured to register a second device, using multiple registration modes, with respect to the first device, including a domain-registration mode, a device-registration mode, and a no-registration mode, wherein the domain-registration mode allows the second device to register with the first device and at least one other device registered with the first device, said at least one other device being in the domain of the first device, the device-registration mode allows the second device to register with the first device and with no other devices, and the no-registration mode does not allow any device to register with the first device, wherein the processor is further configured to receive a selection of one of the multiple registration modes and place the first device in the selected registration mode, and wherein the processor is further configured to receive a registration request message from the second device, the registration request message identifying one of multiple registration modes, with respect to the second device, including at least a device-only mode and a source-domain mode; wherein the domain-registration mode allows the second device to register with the first device and at least one other device registered with the first device, said at least one other device being in the domain of the first device, the device-registration mode allows the second device to register with the first device and with no other devices, and the no-registration mode does not allow any device to register with the first device, wherein the processor is further configured to receive a selection of one of the multiple registration modes and place the first device in the selected registration mode, and wherein the processor is further configured to receive a registration request message from the second device, the registration request message identifying one of multiple registration modes, with respect to the second device, including at least a device-only mode and a source-domain mode; a data storage storing a registration key used to register the second device with the first device; and a network interface configured to exchange messages with the second device for registration depending on the selected registration mode via a network, if the registration mode with the first device is set to the domain-registration mode, the processor is further configured to identify a registration mode with respect to the second device upon receipt of the registration request message from the second device, if the identified registration mode with respect to the second device is the device-only mode, the processor is further configured to allow the second device to register only with the first device, and if the identified registration mode with respect to the second device is the source-domain mode, the processor is further configured to allow the second device to register with not only the first device but also said at least one other device in the domain of the first device.