dns

• Russ's course on OE
• 13 root servers (a-m)
• root, tld (top level domain), authorative server
• recursive/caching/resolver
• ttl is a maximum
• ns = name server - dns server
• a = ipv4 address
• aaaa = ipv6 address
• cname = canonical name (alias)
• dname = domain name - points to another domain (not implemented widely)
• mx = mail exchange
• caa = certificate authority address
• soa = start of authority
• txt
• ptr = pointer (in-addr.arpa)
• nxdomain - domain doesnt exist
• server not found - service doesnt exist
• >512 bytes -> tcp
• dot = dns over tls
• doh = dns over https
• odoh = oblivious doh
• dnssec - adding cryptographic signatures to existing DNS records
• nslookup, dig = domain information groper
• non-authorative answer - it came from cache