Penjelasan tentang DNS dan imlementasinya dalam jarinan Komputer

1. DNS Domain Name System
(Service / Server)
Jaringan Komputer
DNS Rev 03
Imam Suharjo - 2020

2. INTRO
1. Mengapa ada domain?
2. Mengapa ada DNS?
3. DNS digunakan dimana?
4. Bagaimana cara kerja DNS?
5. Siapa yang bisa membuat DNS Server?
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3. Domain Name System (DNS)
• DNS adalah layanan Internet yang menerjemahkan nama domain menjadi
alamat IP. Karena nama domain dengan abjad akan lebih mudah diingat.
Pada dasarnya Internet didasarkan pada alamat IP.
• Setiap kali menggunakan nama domain, oleh karena itu, layanan DNS harus
menerjemahkan namanya ke alamat IP yang sesuai.
• Saat mengunjungi domain seperti mercu.id , komputer Anda mengikuti
serangkaian langkah untuk mengubah alamat web yang dapat dibaca
manusia menjadi alamat IP yang dapat dibaca oleh mesin. Hal ini akan
terjadi setiap kali menggunakan nama domain seperti , membuka situs
web, kirim email atau mendengarkan radio internet.
• Sistem DNS sebenarnya adalah jaringan sendiri. Jika satu server DNS tidak
tahu bagaimana menerjemahkan nama domain tertentu, itu akan meminta
yang lain, dan seterusnya, sampai alamat IP yang benar dikembalikan.
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4. Cara Kerja DNS
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http://www.incisozluk.com.tr/w/domain-name-system-dns-nasil-calisir/

5. Contoh Domain, Domain = Nama
• Indonesia : TLD  cctLD = .ID contoh : mercu.id, jd.id
• SLD  go.id, ac.id, sch.id, co.id, or.id, net.id  ugm.ac.id,
telkom.net.id
• Sub domain : sasa.bejo.test1212.mercu.id
• Cache : isi : TTL
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6. Type Record DNS
• A Address Record Returns a 32-bit IPv4 address, most commonly
used to map hostnames to an IP address of the host,but it is also used for
DNSBLs, storing subnet masks in RFC 1101, etc.
• CNAME Canonical Name Record Alias of one name to another: the
DNS lookup will continue by retrying the lookup with the new name.
• MX Mail Exchange Record Maps a domain name to a list of message
transfer agents for that domain
• AAAA IPv6 Address RecordReturns a 128-bit IPv6 address, most
commonly used to map hostnames to an IP address of the host.
• TXT Text Record Originally for arbitrary human-readable text in a DNS
record. Since the early 1990s, however, this record more often
carriesmachine-readable data, such as specified by RFC 1464, opportunistic
encryption, Sender Policy Framework, DKIM, DMARC, DNS-SD, etc.
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7. Type Record DNS
• PTR Pointer Record Pointer to a canonical name. Unlike a CNAME, DNS processing
stops and just the name is returned. The most common use is for implementing reverse
DNS lookups, but other uses include such things as DNS-SD.
• SRV Service locator Generalized service location record, used for newer protocols
instead of creating protocol-specific records such as MX.
• SPF Sender Policy Framework SPF(99) (from RFC 4408) was specified as part of
the Sender Policy Framework protocol as an alternative to storing SPF data in TXT
records, using the same format. It was later found that the majority of SPF deployments
lack proper support for this record type, and support for it was discontinued in RFC 7208.
• NS Name Server record Delegates a DNS zone to use the given authoritative name
servers
• SOA Start of [a zone of] Authority Record Specifies authoritative information about
a DNS zone, including the primary name server, the email of the domain administrator,
the domain serial number, and several timers relating to refreshing the zone.
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8. 10/06/2021 Imam Suharjo http://imam.mercubuana-yogya.ac.id 8
https://asmed.com/comptia-amazon-aws-dns-records-types/

9. The Domain Name System (aka DNS)
• The DNS is used to resolve human-readable hostnames like
www.Dyn.com into machine-readable IP addresses like
204.13.248.115. DNS also provides other information about domain
names, such as mail services.
• DNS is like a phone book for the Internet. If you know a person’s name
but don’t know their telephone number, you can simply look it up in a
phone book. DNS provides this same service to the Internet.
• When you visit http://dyn.com in a browser, your computer uses DNS
to retrieve the website’s IP address of 204.13.248.115. Without DNS,
you would only be able to visit our website (or any website) by visiting
its IP address directly, such as http://204.13.248.115.
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http://dyn.com/blog/dns-why-its-important-how-it-works/

10. 1. Cache : history (flush)
2. IP DNS
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11. Step 1: Request information
• The process begins when you ask your computer to resolve a
hostname, such as visiting http://dyn.com.
• The first place your computer looks is its local DNS cache, which stores
information that your computer has recently retrieved.
• If your computer doesn’t already know the answer, it needs to
perform a DNS query to find out.
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12. Step 2: Ask the recursive DNS servers
• If the information is not stored locally, your computer queries
(contacts) your ISP’s recursive DNS servers.
• These specialized computers perform the legwork of a DNS query on
your behalf.
• Recursive servers have their own caches, so the process usually ends
here and the information is returned to the user.
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13. Step 3: Ask the root nameservers
• If the recursive servers don’t have the answer, they query the root
nameservers.
• A nameserver is a computer that answers questions about domain
names, such as IP addresses.
• The thirteen root nameservers act as a kind of telephone switchboard
for DNS.
• They don’t know the answer, but they can direct our query to
someone that knows where to find it.
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14. Step 4: Ask the TLD nameservers
• The root nameservers will look at the first part of our request, reading
from right to left — www.dyn.com — and direct our query to the Top-
Level Domain (TLD) nameservers for .com.
• Each TLD, such as .com, .org, and .us, have their own set of
nameservers, which act like a receptionist for each TLD.
• These servers don’t have the information we need, but they can refer
us directly to the servers that do have the information.
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15. • TLD :
• GTLD : > LBH DR 2 CHAR
• ccTLD :
• https://www.iana.org/domains/root/db
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16. Step 5: Ask the authoritative DNS servers
• The TLD nameservers review the next part of our request —
www.dyn.com — and direct our query to the nameservers
responsible for this specific domain.
• These authoritative nameservers are responsible for knowing all the
information about a specific domain, which are stored in DNS records.
• There are many types of records, which each contain a different kind
of information.
• In this example, we want to know the IP address for
www.dyndns.com, so we ask the authoritative nameserver for the
Address Record (A).
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17. Step 6: Retrieve the record
• The recursive server retrieves the A record for dyn.com from the
authoritative nameservers and stores the record in its local cache.
• If anyone else requests the host record for dyn.com, the recursive
servers will already have the answer and will not need to go through
the lookup process again.
• All records have a time-to-live (TTL) value, which is like an expiration
date.
• After a while, the recursive server will need to ask for a new copy of
the record to make sure the information doesn’t become out-of-date.
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18. Step 7: Receive the answer
• Armed with the answer, recursive server returns the A record back to
your computer.
• Your computer stores the record in its cache, reads the IP address
from the record, then passes this information to your browser.
• The browser then opens a connection to the webserver and receives
the website.
• This entire process, from start to finish, takes only milliseconds to
complete.
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19. Domain Name Servers (DNS)
• Domain Name Servers (DNS) are the Internet's equivalent of a phone
book. They maintain a directory of domain names and translate them
to Internet Protocol (IP) addresses.
• This is necessary because, although domain names are easy for
people to remember, computers or machines, access websites based
on IP addresses.
• Information from all the domain name servers across the Internet are
gathered together and housed at the Central Registry. Host
companies and Internet Service Providers interact with the Central
Registry on a regular schedule to get updated DNS information.
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http://www.networksolutions.com/support/what-is-a-domain-
name-server-dns-and-how-does-it-work/

20. Domain Name Servers (DNS)
• When you type in a web address, e.g., www.jimsbikes.com, your
Internet Service Provider views the DNS associated with the domain
name, translates it into a machine friendly IP address (for example
216.168.224.70 is the IP for jimsbikes.com) and directs your Internet
connection to the correct website.
• After you register a new domain name or when you update the DNS
servers on your domain name, it usually takes about 12-36 hours for
the domain name servers world-wide to be updated and able to
access the information. This 36-hour period is referred to as
propagation.
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http://www.networksolutions.com/support/what-is-a-domain-
name-server-dns-and-how-does-it-work/

21. DNS
• Sistem/Server untuk Domain
• Domain = Internet Domain = Nama untuk sebuah host/server/web
• Seperti akses Internet : .com .net .org dll
• Domain lokal : namaku.local (Local domain)
• Tujuannya :
• Seperti Buku Telepon / Mempermudah pemanggilan
• Adanya Domain  Mudah, Sebagai Identitas, Branding (tempo.co an.tv
rcti.tv), Nama yg Public.
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22. Ada apa saja di DNS?
Beberapa isitilah di DNS :
• DNS Server
• DNS resolver
• DNS Client
• IP address – Domain
• Mercu.id – 103.58.111.100
• Mercu.localhost – IP komputer lokal – 127.0.0.1
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23. DNS resolver
• DNS resolver adalah client side dari Domain Name System yang melakukan
query dan menjadi inisiator translasi nama domain ke IP address. DNS
resolver merupakan bagian dari sistem yang memudahkan anda untuk
melakukan browsing dengan menggunakan nama-nama domain dan bukan
lagi menggunakan IP address.
• Contoh ada sebuah perusahaan besar yang memiliki banyak sekali
komputer yang terhubung dengan jaringan internet. Merekapun harus
mengisi/memasukkan DNS resolver untuk mempermudah dalam
mengakses situs-situs di internet. Jika perusahaan tersebut tidak memiliki
DNS server sendiri, maka bisa diisi DNS resolver dari ISP yang digunakan.
• Redirect DNS resolver adalah pemindahan tujuan DNS server dari DNS
resolver. Biasanya hal tersebut dilakukan jika kita memiliki jumlah
komputer yang banyak dan mau mengganti dns resolver dengan yang baru
karena dns resolver yang lama sudah tidak bisa digunakan. Karena jika
dilakukan penggantian secara manual membutuhkan waktu yang sangat
banyak. (Idreg.net)
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24. DNS Server & Client
• Server yang bekerja sebagai DNS :
menyimpan informasi nama
domain dan IP address. IP DNS bisa
digunakan oleh client sebagai
Server DNS di setingan (network).
• Perlu softwrae untuk DNS server
• DNS yg digunakan client bsia > 1,
sebagai alternatif DNS (Primari dan
Secondary DNS).
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25. DNS Server di linux
• DNS Server di linux biasanya dijalankan oleh program yang bernama
named. Program ini merupakan bagian dari paket bind yang
dikoordinasikan oleh Paul Vixie dari The Internet Software
Consortium. Biasanya program ini terletak di /usr/sbin/named dan
dijalankan pada waktu booting dari /etc/rc.d/init.d/named start. Agar
named dijalankan pada setiap booting masukkan named ke daftar
server yang harus distart dengan menggunakan ntsysv.
(pemula.linux.or.id)
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26. Dimana IP DNS digunakan?
DNS Server
PC Client
Router
Perangkat jaringan lain yang membutuhkan akses ke domain
(internet).
Primari dan alterntif : Alternatif jika yang primary bermasalah / tidak
menjawab.
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27. Kenapa DNS serba tahu tentang domain?
• DNS server tidak menyimpan
semua informasi domain di dunia,
namun kalau di tanya (request)
dia tahu dan akan menjawab.
• Dari mana dia bisa tahu?
• DNS Tahu dari Parent(s) DNS 
parent juga DNS.
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28. DNS Cache
• Cache DNS : temporary (Sementara) data (DNS) yang tersimpan di
lokal. Nama, IP, Type, TTL.
• Seberapa lama tersimpan : TTL Time To Life
• TTL : detik, menit, jam hari.
• Sesuai dengan yang membuat / yang punya domain ybs.
• Setelah TTL sebuah domai habis : maka record ttg doamin trsb hilang
sendiri.
• Cara hapus cache : ipconfig /flushdns
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29. Type DNS
Antara lain :
• A : domain – IPv4
• AAAA : domain – IPv6
• CNAME : Domain - Domain
• NS : Domain – Domain (NS)
• SOA : Domain – domain (NS)
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30. • Domain.com ns
• Satu.domain.com
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31. Cache di Mikrotik dan request di Windows
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32. DNS Cache di Windows  Lewat CMD
C:UsersDir-ICT>ipconfig /displaydns
Windows IP Configuration
www.gstatic.com
----------------------------------------
Record Name . . . . . : www.gstatic.com
Record Type . . . . . : 1
Time To Live . . . . : 1080
Data Length . . . . . : 4
Section . . . . . . . : Answer
A (Host) Record . . . : 172.217.27.3
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33. Record file host :
C:WindowsSystem32driversetc
• # ini adalah contoh isi file hosts
127.0.0.1 localhost loopback
127.0.0.1 localdomain
::1 localhost
::1 localhost
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34. Fungsi DNS Cache
• Sebagai Database lokal DNS Sementara
• Mempercepat request DNS berikutnya
• Infomasi record DNS dari DNS server akan tersimpan sementara di
cache selama TTL.
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35. Kasus : “Internet Positif” /”Nawala DNS”
• Karena yang digunakan adalah
DNS “khusus”
• Bisa juga melalukan filtering /
firewall DNS.
• Client tanya ke DNS ISP
• DNS ISP menggunakan parent
DNS yg terfilter misal DNS
Internet positif/ nawala
• Informasi DNS akan terfilter.
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36. Kasus Domain
pindah
Hosting
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37. Tambahan : Koneksi tidak langsung
• Proxy
• IP Proxy
• Web Proxy
• VPN
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38. Koneksi tidak langsung VPN / Proxy
• Koneksi Normla Biru, jika biru
ke arah web/server tujuan d
blokir bisa menggunakan pihak
ketiga (proxy/VPN).
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39. Related Terms DNS
• DNS parking (domain parking)
• domain name
• split DNS
• Berkeley Internet Name Domain
• round robin DNS
• child domain
• domain name naming authority
• domain name dispute
• domain name registrar
• domain name resolvers
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http://www.webopedia.com/TERM/D/DNS_parking.html

40. Tool eksternal terkait DNS
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41. dnschecker.org
• Digunakan utuk menguji apakah Sebuah domain sudah resoved engan
baik di berbagai lokasi
• Bisanya digunakan saat sebuah domain/sub domain baru dibuat, ada
perpindahan server (alamat IP), setelah terjadi gangguan dll
• Hasil test mennjukan status OK (Centang) dari berbagai lokasi test.
• Jika ada yang tanda silang, bisa jadi DNS / Domain kita tidak bisa
diakses dari lokasi tersebut (Mungkin masalah local di suatu area)
seperti domain di Blokir, masalah DNS resolver yang mereka gunakan,
dll.
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42. https://dnschecker.org (Tampilan awal)
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43. https://dnschecker.org (Tampilan Hasil)
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44. Open DNS Cache Check
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45. Bahan Bacaan
• Chris Gonyea, DNS: Why It’s Important & How It Works, http://dyn.com/blog/dns-why-its-
important-how-it-works di akses 31 Mei 2017
• Vangie Beal, DNS, http://www.webopedia.com/TERM/D/DNS.html di akses 31 Mei 2017
• Managing Domain Name Servers : What Is A Domain Name Server (DNS) And How Does It Work,
http://www.networksolutions.com/support/what-is-a-domain-name-server-dns-and-how-does-
it-work/
• Apa itu Redirect DNS Resolver, https://www.idreg.net/apa-itu-redirect-dns-resolver/
• Seting DNS Server, https://pemula.linux.or.id/admin/setting-dns-server.html
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