A method of processing data in a digital receiving apparatus, the method including receiving a broadcast signal including low level signaling data, wherein the low level signaling data is carried via a specific data pipe (DP), wherein the low level signaling data includes service category information, the service category information is used to identify an AV service, an audio only service or an ESG (electronic service guide) service, wherein the low level signaling data is used to provide bootstrap information that allows the receiving apparatus to discover at least one service layer signaling information, wherein the bootstrap information includes URL data for a first service layer signaling information when the first service layer signaling information is transmitted via a broadband network, and wherein the bootstrap information includes a destination user datagram protocol (UDP) port number and a destination internet protocol (IP) address for a second service layer signaling information when the second service layer signaling information is transmitted via a broadcast network; and parsing the low level signaling data included in the broadcast signal, wherein the low level signaling data is parsed, and then the first service layer signaling information or the second service layer signaling information is processed.