The CCITT considering (a) that errors have to be detected and corrected with a very high degree of reliability; (b) that some error correction procedures may be more advantageous than others depending on transmission delays in the network and on the distribution (with time) of errors; (c) that the distribution (with time) of errors at the ends of a path may depend on forward error correction procedures implemented in one or more of the path segments; (d) that the applicability of some error correction procedures may be affected by the number of satellite systems in the connection, which may be in national or international links or in the Maritime Mobile Service; (e) that different error correction procedures may be concatenated in some connections.