Data distribution system

A data processing system comprising a plurality of data processing machines at a site, wherein at said site:

• the data processing machines are each configured to receive data as a multicast from a central source remote from the site;
• one of the data processing machines is designated as a site master;
• the remaining data processing machines are configured to report missing data portions to the site master;
• and
• the site master is configured to consolidate reports of missing data portions, and to request missing data portions from the central source;
• and wherein the data processing machines are configured to receive missing data portions in a further multicast from the central source.

A data processing machine at site where there is a plurality of data processing machines, wherein said data processing machine is configured to be capable of adopting a first operational state and a second, alternate operational state, and to choose between the first and second operational states, wherein:

• (i) in the first operational state said data processing machine is configured to receive data as a multicast from a central source remote from the site;
• to report missing data portions to another data processing machine at the site designated as a site master;
• and to receive missing data portions in a further multicast;
• and
• (ii) in the second operational state the first data processing machine is configured to act as a site master which:
• (a) receives data as a multicast from a central source remote from the site;
• and
• (b) receives reports of missing data portions from the remainder of the plurality of data processing machines at the site, consolidates the reports of missing data portions, and requests missing data portions from the central source.

A computer readable medium having computer executable instructions adapted to cause a data processing machine to be configured so that:

• said data processing machine can adopt a first operational state and a second operational state, and can elect between the first and second operational states, wherein:
• (i) in the first operational state said data processing machine is configured to receive data as a multicast from a central source remote from the site;
• to report missing data portions to another data processing machine at the site designated as a site master;
• and to receive missing data portions in a further multicast;
• and
• (ii) in the second operational state the first data processing machine is configured to act as a site master which:
• (a) receives data as a multicast from a central source remote from the site;
• and
• (b) receives reports of missing data portions from the remainder of the plurality of data processing machines at the site, consolidates the reports of missing data portions, and requests missing data portions from the central source.

A central server configured for distributing data to a plurality of remote data processing machines arranged in a plurality of sites, there being a plurality of said data processing machines at each said site, wherein the server is configured:

• (i) to transmit the data as a global multicast to the data processing machines;
• (ii) to receive from a master data processing machine at each remote site, a notification of missing data portions reported to the master data processing machine by other of the other machines at the site;
• (iii) to consolidate reports of missing data portion received by the source from site masters at different remote sites;
• and subsequently
• (iv) to transmit the missing data to the plurality of remote data processing machines by means of a further global multicast.