Due to the deficiencies of the original RIP specification, RIP version 2 (RIPv2) was developed in 1993, published as RFC 1723 in 1994, and declared Internet Standard 56 in 1998. It included the ability to carry subnet information, thus supporting Classless Inter-Domain Routing (CIDR). To maintain backward compatibility, the hop count limit of 15 remained. RIPv2 has facilities to fully interoperate with the earlier specification if all "Must Be Zero" protocol fields in the RIPv1 messages are properly specified. In addition, a "compatibility switch" feature allows fine-grained interoperability adjustments.