EDNS

An extension to the original DNS (glossary)DNS Domain Name System The internet's directory that links domain names to computer addresses. Full definition of DNS protocol that lets DNS messages be larger and carry extra options. DNSSEC (glossary)DNSSEC Domain Name System Security Extensions Digital signatures that prove DNS answers are genuine and unchanged. Full definition of DNSSEC depends on it, and it also carries features such as hints about the user's network. Servers and firewalls that handle it badly can cause lookups to fail.