Domain name system (dns)
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The document discusses the Domain Name System (DNS) and how it works. DNS is an internet directory service that maps hostnames to IP addresses, allowing users to use names instead of numbers. It uses a distributed, hierarchical system of name servers to perform this name resolution in a scalable way. DNS caches mappings for performance, starting queries at the highest level domains and following delegations between servers until the answer is found. DNS has become a major attack vector, so protection of DNS infrastructure and traffic is important.
Domain name system (dns)
- 2. WHAT IS DNS? Internet Directory Service. A client-server application that maps host names into their corresponding IP addresses. Mapping host names into their corresponding IP addresses is called name resolution or name translation or name mapping or Address Resolution. 2
- 3. WHY WE NEED DNS? As the system grew, HOSTS.TXT had problems with: Scalability (traffic and load) Reliability Dynamicity Name collisions Consistency 3
- 4. WHY WE NEED TO USE NAME INSTEAD OF IP NUMBERS? IP addresses are difficult to remember IP addresses can change •Problem: Network only understands numeric addresses •Solution: Use alpha numeric names to refer to hosts Add a distributed, hierarchical protocol (called DNS) to map between alpha numeric host names and IP addresses. 4
- 5. THE DNS NAME SPACE The Internet is divided into more than 200 top-level domains Domain: It is sub tree of the domain name space and consists of group of hosts that are under the administrative control of a single entity such as a company or a government agency Each domain is sub divided into sub domains The leaves represent domains that have no sub domains A leaf domain may contain a single host, or represent a company with thousands of hosts 5
- 6. THE DNS NAME SPACE Top level domains A portion of the Internet domain name space 6
- 7. DOMAIN Domain is a sub tree of domain name space Root node is empty Domain is divided into sub-domains Domain name is the domain name of the node at the top of the sub tree 7 Sub Sub Sub
- 8. HIERARCHY OF NAME SERVERS DNS is a distributed data base system Uses a large number of computers called name servers Organized in a hierarchical way and distributed all over the world No single host has all the exact mappings for all the hosts in the Internet 8
- 9. HOW DNS WORKS A network host is configured with an initial cache (so called hints) of the known addresses of the root name servers. Such a hint file is updated periodically by an administrator from are liable source. DNS zone is loaded on authoritative servers keep in sync using information in SOA RR via AXFR, IXFR or other means. DNS caches only store data for a short time. DNS Recursive Resolvers start at “longest match” on query name they have when looking for data, and follow delegations until an answer or a negative answer is received. 9
- 10. HOW DNS WORKS 10
- 11. ADVANCED DNS PROTECTION DNS is one of the fastest growing attack vectors. DNS is now tied with http as the top targeted service of application layer attacks and is the number one protocol used in reflection/ amplification attacks. DNS-based attacks can bring down the network or redirect users away from your website. 11
- 12. INFOBLOX ADVANCED DNS PROTECTION 12
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