A method for fabricating air media layer within the semiconductor optical device is provided. With the under-body frame, it is possible to increase fixation security of a trailing arm of a suspension device and enhance safety of inside parts of a vehicle when a rear impact occurs. The content subscriber, in turn, accesses the presence information via the multicast transmission channel. The correction packet may be received at the destination device, and a determination may be made as to whether at least one of the plurality of packets transmitted to the destination device is a lost packet that has not been received at the destination device. Moreover, it relates to a corresponding apparatus for allocating at least one parameter to at least one transmission channel at an interface disposed between a first node and a second node of a transmission system.