Domain Name System (for Linux)

Apa itu DNS? Sebuah protokol layer 7 yang berisi database records (domain +ip) yang bertugas memappingkan ip dengan hostname (domain name) yang diminta client.

DNS Host di Internet menggunakan alamat IP sebagai identitas ex: 202.95.158.17 Numeric ID tidak human friendly Alphanumeric lebih mudah diingat

Mengapa perlu DNS? Perlu skema pemetaan antara IP dengan nama Pada awalnya menggunakan file

Hosts file tidak praktis Network berkembang, makin sulit update database Solusi: menggunakan DNS RFC 1034 dan 1035 Port 53

Primary Purpose Resolve hostnames to IP addresses www.planeted.net  209.175.170.14 Resolve IP addresses to hostnames 209.175.170.14 www.planeted.net

Cara kerja DNS Hirarki proses Database distribution

Terminologi Terms Domain – a collection of records with a contiguous namespace mydomain.com Subdomain – a collection of records with a contiguous namespace that are hierarchically beneath another domain newyork.mydomain.com cincinnati.mydomain.com Zone – a collection of records that comprise a DNS domain Name Server or DNS Server A server capable of either answering queries for records it owns or answering queries on behalf of DNS clients, or both.

Terminologi lanjutan Terms (continued) Record – either a forward or reverse name mapping “A” Record – Maps hostname to IP Address www.planeted.net.  209.175.170.14 “CNAME” Record – Maps an alias to a hostname www.planeted.net.  redmond.jeffneddie.com. PTR Record – Maps an IP address to a hostname 209.175.170.14  redmond.jeffneddie.com. MX Record – Defines a mail exchanger for a host or domain MX  mymailserver.mydomain.com. SOA Record – Start of Authority – contains a list of authoritative name servers, TTL values, etc. SOA  mydomain.com. NS Record – Lists authoritative name servers for a domain NS  mydnsserver.mydomain.com. SRV Record – Maps a service to a hostname LDAP  mydc.mydomain.com.

Root DNS Server edu DNS Server Org DNS Server Com DNS Server

DNS name space Top Level Domain Second Level Domain Generic (com, edu, net, biz, org dll) Country code ( id, au, my, jp, sg dll) Second Level Domain

DNS name space Second level domain: co.id ac.id or.id Dll

Server dan client Name server Resolver (client) Menyimpan/mengatur domain name Melayani permintaan dari client Resolver (client)

Resolver Client part of DNS Trigger DNS query Bagian dari OS

Name Server Authoritative DNS Server DNS Server Organisasi, melayani mapping hostname ke IP yang ada di org tsb Di kelola oleh org tsb atau ISP

Name Server Local Name Server Dimiliki oleh setiap ISP Default name server Jika sebuah host memilik DNS query, query tsb dikirim ke name server lokal

DNS Name Resolution Iterative (request perulangan sampai kondisi terpenuhi) Recursive (request sekali, yang penting kondisi terpenuhi)

Iterative

Recursive Request it.intel.com Root name server Name server for .com client name server for intel.com name server for it.intel.com