Content information is multicast via a data network to a plurality of receivers, using data packets in a transport stream. The content information is encapsulated according to a container format standard that allows an optional field in a packet header. Each data packet forms a payload of a datagram in a connectionless communication protocol. The optional field in each data packet is used to carry an identifier for identifying the data packet in a pre-determined sequence of the data packets. The use of the optional field enables packet loss detection at the receiver.