1. A system for backup replication, comprising: a processor configured to: determine data present in a most recent backup not present in a previous backup, wherein the data comprises one or more data segments; transmit an extent specification to a replica backup system, wherein the extent specification comprises a description of regions of unchanged data from the previous backup to the most recent backup; transmit a checksum for the most recent backup to the replica backup system; transmit data segment fingerprints of the one or more data segments to the replica backup system; receive one or more data segment requests from the replica backup system, wherein a data segment request of the one or more data segment requests comprises an indication that a data segment from the transmitted data fingerprints is not previously stored on the replica backup system and is requested of the data storage system; and transmit the requested data segment from the data storage system to the replica backup system, wherein the transmitted data segment is combined with data segments previously stored on the replica backup system into a replica backup file using the transmitted extent specification; and a memory coupled to the processor and configured to provide the processor with instructions.