DNS Domain Name system DNS Hierachical Video Domain

DNS Domain Name system

DNS Hierachical Video: Domain Name System (DNS) How It Works

History • ARPANET (Advanced Research Projects Agency Network) • Massachusetts Institute of Technology and the Defense Advanced Research Projects Agency (DARPA) • Packet switching

ARPA Net

History • Host. txt at Sri Computer(Stanford Research Institute) • 1984(2527) Berkley students ����� Berkeley Internet Name Domain (BIND)

History

DNS Name Server • DNS = Internet Name Server+DNS Protocol • Server ���� DNS Records • A(Address) Record • NS(Name Server) Record • MX(Mail Exchange) Record • ….

DNS Name Server

Domain Name Space • Tree of Domain Name • Node ���� Leaf ��������� (Zone)

Domain Name Space • Tree ������ Zones ����� Root zone • DNS Zone = ����� node ������� (Autoritative Name Server) • ���� th -> thnic server(root of th) • ac -> thnic server(zone ac. th) • psru -> ns. psru. ac. th(zone psru. ac. th) • Nurse of psru -> mail. science. psru. ac. th(zone science. psru. ac. th)

Domain Name Space th ac psru science

DNS Root Zone • Top-level DNS Zone • By IANA(Internet Assigned Numbers Authority) • 13 Clusters(Why 13? ? ? ) • a. root-servers. net to m. root-servers. net • . com, . net, . org, . th

DNS Root Zone

DNS Root Server http: //root-servers. org/

Domain Name Fomulation • Domain name ����� 1 ��������� Label(name space) • ��������� “. ”(��� ) ���� www. psru. ac. th • ������� Domain name ��� toplevel domain ���� www. psru. ac. th ����� top-level domain ��� th

Domain Name Fomulation • ����������� • Label �������� subdomain �������� www. psru. ac. th – ac ��� subdomain ��� th – psru ��� subdomain ��� ac – ����� root domain �� subdomain ��� 127 sub.

Domain Name Fomulation • ����� label ����� 63 ���� • Full domain name ����� 253 ���� • DNS Name ������� LDH(Letter, Digit, Hyphen) ����������� (Hyphe n)

Domain Name Fomulation

Name Server • • • DNS use Distributed Database System Client-Server Model(53 udp/tcp) Node of Database is “Name Server” 1 Domain – 1 Authoritative DNS Server Top-level domain -> root name server

Domain Name Space th ac psru sciencer

Authoritative Name Server • Name server : ����������� • Master / Slave • Authoritative Name Server • Non-Authoritative Name Server

Authoritative Name Server

Recursive and caching name server • Authoritative name server 1 ��� ? ? • �������� -> �� DNS Traffic -> Caching name server • 1 Authoritative & 1 caching name server

Address resolution mechanism • ������� root hint ������ dns server • ��� root server ��������� top-level domain(������ ( • ��� server ������ top-level domain ��� server ������ second level domain • ��� level ������

Address resolution mechanism

Client Lookup

DNS resource records • Resource record(RR) : Basic data element Type Rdata Name Class

DNS resource records

Zones

Zones • Standard Primary : ������ zone • Standard Secondary : ������ zone • Zone Transfer

Zone Files Zone Properties NS of Zone Address Record

DNS Zone Transfer • • Full & Increment 53/TCP with server-client master(SOA) -> slave ����� serial

DNS Zone Transfer

Zone Transfer Ploblems • Serial number change • Serial number comparison(YYYYMMDD) • Exposure of Data

Reverse DNS lookup • • ������� IP -> domain name ������ in-addr. arpa 202. 28. 249. 0 -> 249. 28. 202. in-addr. arpa PTR Record

Reverse DNS lookup

Round Robin DNS

DNS Tools • Who is & Lookup – http: //www. dnsstuff. com – http: //network-tools. com – http: //www. 4 dnstools. com/ – http: //www. dnswatch. info/ – http: //www. mxtoolbox. com – http: //www. dnstools. com/

DNS Tools • Nslookup – Server – Set type=xx – Set domain=xxx. domain. com – ls –d xxx. domain. com