Random server selection for retrieving fragments under changing network conditions

摘要

An assembling device obtaining enough erasure-coded fragments from fractional-storage CDN servers for reconstructing a first set of segments including at least one segment. The communication between the assembling device and the servers is subject to at least one type of communication fault, and the assembling device handles the communication faults by approximately randomly selecting on-the-fly servers from which to obtain additional fragments instead of fragments that failed to be obtained.

主权项

1. A method for retrieving fragments, comprising:
requesting by an assembling device from a first set of servers erasure-coded fragments usable to decode a first nonempty set of erasure-coded segments; the first set of servers configured to have an aggregated bandwidth significantly greater than incoming bandwidth of the assembling device, configured to store enough of the erasure-coded fragments to have a redundancy factor greater than one, and each of the servers in the first set configured to store at least one erasure-coded fragment but less the minimum data required to reconstruct the first nonempty set of erasure-coded segments; controlling the requested fragment rate, by the assembling device, using a fragment pull protocol; on-the-fly and while requesting the fragments, selecting randomly or pseudo randomly at least one server from a second set of servers storing fragments usable to reconstruct the first nonempty set of erasure-coded segments; and shortly thereafter requesting on-the-fly, by the assembling device from the at least one randomly selected server, additional fragments instead of fragments that failed to be retrieved.