A method of receiving broadcast data at a receiver, the method comprising: receiving a service discovery record including first information on a main service and second information on a plurality of preview services of the main service, and extracting the first information on the main service and the second information, wherein each preview service includes a service constructed with a data size or a screen size smaller than that of the main service, wherein the first information includes streaming type information indicating whether a streaming of the service uses a Real Time Protocol, RTP, or a direct User Datagram Protocol, UDP, and wherein the second information further includes preview service information indicating a presence or non-presence of the each preview service, preferred information indicating preferred preview service among the plurality of preview services, DVB triplet information specifying DVB triplet information of each preview service, service location information indicating an address at which the each preview service exists, and max bitrate information indicating maximum bitrate for data of the each preview service; generating a channel map using information included in the received service discovery record; receiving (S1020, S1040) a user request for switching to a channel for providing a service related to the main service; accessing (S1022, S1044) a first server providing the main service based on the extracted first information; receiving (S1028, S1046) first stream including the main service from the first server; and determining whether a selected preview service of the plurality of received preview services is stored in a storage medium of the receiver due to preview service data buffering in advance being set for that channel, wherein the selected preview service is selected based on the preferred information; accessing a second server providing the plurality of preview services based on the extracted second information and receiving the plurality of preview services from the second server when the selected preview service is not stored in the storage medium, displaying (S1032, S1050) the selected preview service which is stored in the storage medium or included in the plurality of received preview services on a screen during receiving the first stream based on the step of determining, wherein the selected preview service is discriminated from the plurality of preview services by DVB triplet information when the plurality of preview services are carried by a single transport stream, wherein the DVB triplet information includes network identification information, transport stream identification information and service identification information. receiving a service discovery record including first information on a main service and second information on a plurality of preview services of the main service, and extracting the first information on the main service and the second information, wherein each preview service includes a service constructed with a data size or a screen size smaller than that of the main service, wherein the first information includes streaming type information indicating whether a streaming of the service uses a Real Time Protocol, RTP, or a direct User Datagram Protocol, UDP, and wherein the second information further includes preview service information indicating a presence or non-presence of the each preview service, preferred information indicating preferred preview service among the plurality of preview services, DVB triplet information specifying DVB triplet information of each preview service, service location information indicating an address at which the each preview service exists, and max bitrate information indicating maximum bitrate for data of the each preview service; generating a channel map using information included in the received service discovery record; receiving (S1020, S1040) a user request for switching to a channel for providing a service related to the main service; accessing (S1022, S1044) a first server providing the main service based on the extracted first information; receiving (S1028, S1046) first stream including the main service from the first server; and determining whether a selected preview service of the plurality of received preview services is stored in a storage medium of the receiver due to preview service data buffering in advance being set for that channel, wherein the selected preview service is selected based on the preferred information; accessing a second server providing the plurality of preview services based on the extracted second information and receiving the plurality of preview services from the second server when the selected preview service is not stored in the storage medium, displaying (S1032, S1050) the selected preview service which is stored in the storage medium or included in the plurality of received preview services on a screen during receiving the first stream based on the step of determining, wherein the selected preview service is discriminated from the plurality of preview services by DVB triplet information when the plurality of preview services are carried by a single transport stream, wherein the DVB triplet information includes network identification information, transport stream identification information and service identification information.