A system comprising: a digital component request server configured to receive, from each of multiple client devices, a digital component request for a supplemental digital component to be presented in an additional multicast stream that is different to a multicast stream for delivering streaming content to the respective client device, wherein a number of additional multicast streams that are capable of being distributed to the multiple client devices over an available bandwidth is less than a total number of the multiple client devices; a digital component distribution server configured to i) select supplemental digital components to distribute over at least a portion of each of the additional multicast streams that are capable of being distributed, the supplemental digital components being selected for a respective one of the additional multicast streams being different to the supplemental digital component selected for each of the other additional multicast streams, and ii) assign one group of a plurality of groups of the multiple client devices to a respective one of the additional multicast streams that distribute the supplemental digital components, each said group being assigned an additional multicast stream that is different to the additional multicast stream assigned to each of the other groups of multiple client devices; an instruction generation server configured to generate instructions for each of the multiple client devices to tune to the respective additional multicast streams assigned to the group of multiple client devices that includes the different client device that submitted the request; and a ping address generation server configured to generate a client configurable ping address that includes a placeholder for insertion of a device identifier by the client device that submitted the request to indicate whether that client device tuned to the respective additional multicast stream. a digital component request server configured to receive, from each of multiple client devices, a digital component request for a supplemental digital component to be presented in an additional multicast stream that is different to a multicast stream for delivering streaming content to the respective client device, wherein a number of additional multicast streams that are capable of being distributed to the multiple client devices over an available bandwidth is less than a total number of the multiple client devices; a digital component distribution server configured to i) select supplemental digital components to distribute over at least a portion of each of the additional multicast streams that are capable of being distributed, the supplemental digital components being selected for a respective one of the additional multicast streams being different to the supplemental digital component selected for each of the other additional multicast streams, and ii) assign one group of a plurality of groups of the multiple client devices to a respective one of the additional multicast streams that distribute the supplemental digital components, each said group being assigned an additional multicast stream that is different to the additional multicast stream assigned to each of the other groups of multiple client devices; an instruction generation server configured to generate instructions for each of the multiple client devices to tune to the respective additional multicast streams assigned to the group of multiple client devices that includes the different client device that submitted the request; and a ping address generation server configured to generate a client configurable ping address that includes a placeholder for insertion of a device identifier by the client device that submitted the request to indicate whether that client device tuned to the respective additional multicast stream.