Networking

Question 1

DNS

Answer 1

Distributed databases
Accessed by resolvers gethostbyname and gethostbyaddr
Resolvers are part of program. protocols are part of kernel

Question 2

When does dns use tcp and when it uses udp

Answer 2

Resolver will ask a question over udp. If the response comes back with tc field ser, that means the response was truncated at 512 bytes. So it should retry with tcp. Why truncated at 512…because that is the udp datagram size

Zone transfers from secondary server to primary happens over tcp