The Generalized Object Encoding (GOE) Approach for the Forward Erasure Correction (FEC) Protection of Objects and its Application to Reed-Solomon Codes over GF(2 8)
Résumé
This document describes a Generalized Object Encoding (GOE) approach for the protection of one or multiple objects, using one or several FEC schemes, in the context of a Content Delivery Protocol (CDP) like FLUTE/ALC, FCAST/ALC or FCAST/NORM. In RFC5052, the encoding process is determined by the object (e.g., file) boundaries, i.e., the same code is applied to the whole object that has been submitted to the CDP by the user. The GOE approach instead decouples the definition of source blocks that are FEC encoded from the natural object boundaries. More precisely, either different portions of a given object can be protected with different FEC codes (i.e., portions of different nature and/or with different code rates), with a possible overlapping, or at the opposite, different consecutive objects can be protected globally through a single FEC encoding. If a GOE FEC Scheme defines how to create and process repair packets using the GOE approach, source objects must be encoded with a standard No-Code FEC Scheme. Therefore the same flow of source packets can be shared by different flows of repair packets, using different systematic GOE FEC schemes. An additional benefit is that the GOE approach is backward compliant since the source packets can be processed by receivers that do not support any GOE FEC scheme by simply discarding the repair packets. The present document first of all introduces the GOE approach. It then defines the GOE Reed-Solomon FEC Scheme for the particular case of Reed-Solomon codes over GF(2^^8) and no encoding symbol group, the GOE equivalent to FEC Encoding ID 5 defined in RFC5510.