An LDAPv2 implementation has no mechanism to transfer attribute types with options including the binary transfer and language tag options. LDAPv2 requires these attributes to be transferred using their string encoding. A dual server should be prepared to convert between a syntax's string and binary encodings. It should be noted that certain syntaxes, such as certificate, have protocol specific requirements which restrict possible conversions. LDAPv2 has no mechanism to support attribute descriptions containing language tags.
Filter supports a choice of extensibleMatch.
An LDAPv2 does not. A LDAPv2 implementation would likely treat an unknown filter choice as a protocol error. Empty 'or' and 'and' filters sets LDAPv3 requires 'and' and 'or' filter sets to be non-empty. However, as defined filter string representation cannot represent an empty filter set, support for empty filter sets cannot be presumed to be present. Dual implementations should avoid empty 'or' and 'and' filter sets.