Domain Name System (DNS)

Network Service -2

What Is a Domain Namespace?

Root DomainRoot Domain

SubdomainsSubdomains

Second-Level DomainSecond-Level Domain

Top-Level DomainTop-Level Domain

FQDN:server1.sales.south.nwtraders.com

FQDN:server1.sales.south.nwtraders.com

southsouth

nwtradersnwtraders

comcom

salessales

westwest easteast

orgorgnetnet

Host: server1Host: server1

Network Service -3

Standards for DNS Naming

The following characters are valid for DNS names:

A-Z

a-z

0-9

Hyphen (-)

The underscore (_) is a reserved character

Network Service -4

What Are the Components of a DNS Solution?

DNS Servers on the InternetDNS ServersDNS Clients

Root “.”Root “.”

.com.com

.edu.eduResourceRecord

ResourceRecord

ResourceRecord

ResourceRecord

Network Service -5

What Is a DNS Query?

DNS clients and DNS servers both initiate queries for name resolution

An authoritative DNS server for the namespace of the query will either: Check the cache, check the zone, and return the

requested IP address Return an authoritative, “No”

A non-authoritative DNS server for the namespace of the query will either: Forward the unresolvable query to a specific query

server called a Forwarder Use root hints to locate an answer for the query

DNS server 에 name resolution 요청하는 방법인 DNS Query가 Recursive( 재귀 ) 와 iterative( 반복 ) Query 2 가지가 있다 . DNS server 에 name resolution 요청하는 방법인 DNS Query가 Recursive( 재귀 ) 와 iterative( 반복 ) Query 2 가지가 있다 .

Network Service -6

How Recursive Queries Work

Computer1Computer1

Recursive query for mail1.nwtraders.com

172.16.64.11

Recursive( 재귀 ) Query 는 DNS client 가 Local DNS Server 에 Query 를 보내는 종류의 Query 로 Query 에 대한 응답이 올 때 까지 Query 를 계속적으로 Query 보내는 방법을 말한다 .

Recursive( 재귀 ) Query 는 DNS client 가 Local DNS Server 에 Query 를 보내는 종류의 Query 로 Query 에 대한 응답이 올 때 까지 Query 를 계속적으로 Query 보내는 방법을 말한다 .

DNS server checks the forward lookup zone and cache for an answer to the query

DNS server checks the forward lookup zone and cache for an answer to the query

Database

Local DNS ServerLocal DNS Server

Network Service -7

How Root Hint Works

Root hints 란 Local DNS Server 에 Query 에 대한 IP addresses 정 보가 없을 때 Local DNS Server 가 DNS root servers 에게 Query 를 보내는 것을 말한다 .

Root hints 란 Local DNS Server 에 Query 에 대한 IP addresses 정 보가 없을 때 Local DNS Server 가 DNS root servers 에게 Query 를 보내는 것을 말한다 .

microsoftmicrosoft

Cluster ofDNS Servers

Cluster ofDNS Servers

Root HintsRoot Hints

DNS ServerDNS Server

Cluster of Root (.) Servers

Cluster of Root (.) Servers

comcom

Computer1Computer1

Network Service -8

How Iterative Queries Work

Iterative( 반복 ) Query 란 Root server 가 하는 것이다 . 이름 풀이를 할 때 영역 파일에 정보를 가지고 있을 때만 이름 풀이를 할 것이다 . 만일 그렇지 않다면 다른 DNS server 들에 Query 를 보내는 것을 말한다 .

Iterative( 반복 ) Query 란 Root server 가 하는 것이다 . 이름 풀이를 할 때 영역 파일에 정보를 가지고 있을 때만 이름 풀이를 할 것이다 . 만일 그렇지 않다면 다른 DNS server 들에 Query 를 보내는 것을 말한다 .

Computer1Computer1

Local DNS Server

Local DNS Server

nwtraders.comnwtraders.com

Root Hint (.)Root Hint (.)

.com.com

Recu

rsive

que

ry fo

r

mail

1.nw

trade

rs.co

m17

2.16

.64.

11Iterative Query

Iterative Query

Iterative Query

Ask .com

Ask nwtraders.com

Authoritative Response33

22

11

Network Service -9

How Forwarders Work

Forwarder( 전달자 ) 는 외부 DNS(Domain Name System) 이름에 대한 DNS 쿼리를 네트워크 외부의 DNS 서버에 Forward( 전달 ) 하는 데 사용되는

네트워크의 DNS 서버입니다 .

Forwarder( 전달자 ) 는 외부 DNS(Domain Name System) 이름에 대한 DNS 쿼리를 네트워크 외부의 DNS 서버에 Forward( 전달 ) 하는 데 사용되는

네트워크의 DNS 서버입니다 .

Computer1Computer1nwtraders.comnwtraders.com

Root Hint (.)Root Hint (.)

.com.com

Iterative Query

Iterative Query

Iterative Query

Ask .com

Ask nwtraders.com

Authoritative Response

Local DNS Server

Local DNS Server

ForwarderForwarder

Recursive query for mail1.nwtraders.com

172.16.64.11

172.1

6.64.1

1

Recu

rsive

Que

ry

Network Service -10

How DNS Server Caching Works

Caching 이란 최근에 접근한 정보를 액세스를 빠르게 하기 위해서 메모리에 저장하는 과정을 말한다 .Caching 이란 최근에 접근한 정보를 액세스를 빠르게 하기 위해서 메모리에 저장하는 과정을 말한다 .

Where’s Client A?

Where’s Client A?

Client1Client1

Client2Client2

ClientAClientA

ClientA is at 192.168.8.44ClientA is at 192.168.8.44

Where’s Client A?

Where’s Client A?

ClientA is at 192.168.8.44ClientA is at 192.168.8.44

Caching Table

Host NameIP

AddressTTL

clientA.contoso.msft.

192.168.8.44

28 second

s

Network Service -11

How DNS Data Is Stored and Maintained

DNS ServerDNS Server

Zone File: Zone File: Training.nwtraders.msft.dnsTraining.nwtraders.msft.dns

DNS ClientADNS ClientA

Resource records for the zone

training.nwtraders.msft

Host name IP address

DNS ClientA192.168.2.4

5

DNS ClientB192.168.2.4

6

DNS ClientC192.168.2.4

7

DNS ClientBDNS ClientBDNS ClientCDNS ClientC

Namespace: training.nwtraders.msft

Resource record (RR) 는 DNS 쿼리를 처리하는데 사용되는 정보를 포함하고 있는 표준 DNS 데이터베이스 구조 Resource record (RR) 는 DNS 쿼리를 처리하는데 사용되는 정보를 포함하고 있는 표준 DNS 데이터베이스 구조

zone 은 DNS 데이터베이스에서 DNS 서버에 의해 하나의 별개 항목으로 관리되는 DNS 트리의 연속되어 있는 부분 . zone 은 DNS 데이터베이스에서 DNS 서버에 의해 하나의 별개 항목으로 관리되는 DNS 트리의 연속되어 있는 부분 .

Network Service -12

What Are Resource Records and Record Types?

Record type Description

A Resolves a host name to an IP address

PTR Resolves an IP address to a host name

SOA The first record in any zone file

SRV Resolves names of servers providing services

NS Identifies the DNS server for each zone

MX The mail server

CNAME Resolves from a host name to a host name

Network Service -13

What Is a DNS Zone?

NwtradersNwtraders

WestWestSouthSouth

SupportSupportSalesSales TrainingTraining

NorthNorth

Network Service -14

What Are DNS Zone Types?

Zones Description

Primary

Read/write copy of a DNS database

Secondary

Read-only copy of a DNS database

Stub

Copy of a zone containing limited records

Read/Write

Read-Only

Copy oflimitedrecords

Network Service -15

How to Change a DNS Zone Type

Your instructor will demonstrate how to change a DNS zone typeYour instructor will demonstrate how to change a DNS zone type

Network Service -16

What Are Forward and Reverse Lookup Zones?

Namespace: training.nwtraders.msft.

DNS Client1DNS Client1DNS Client2DNS Client2

DNS Client3DNS Client3

DNS Server Authorizedfor training

DNS Server Authorizedfor training Forwa

rd zone

Training

DNS Client1

192.168.2.45

DNS Client2

192.168.2.46

DNS Client3

192.168.2.47

Reverse

zone

1.168.192.in-

addr.arpa

192.168.2.45

DNS Client1

192.168.2.46

DNS Client2

192.168.2.47

DNS Client3

DNS Client2 = ?DNS Client2 = ?

192.168.2.46 = ?192.168.2.46 = ?

Network Service -17

How DNS Zone Transfers Work

Secondary Server Primary andMaster Server

SOA query for a zone

SOA query answered

IXFR or AXFR query for a zone

IXFR or AXFR query answered

(zone transfer)

DNS zone transfer 는 DNS servers 에서 zone data 를 synchronization( 동기화 ) 및 authoritative( 인증 ) 작업을 한다 .

DNS zone transfer 는 DNS servers 에서 zone data 를 synchronization( 동기화 ) 및 authoritative( 인증 ) 작업을 한다 .

11

22

33

44

Network Service -18

How DNS Notify Works

Secondary Server Primary andMaster Server

DNS notify

Zone transfer

DNS notify 는 Primary 의 Zone 데이터베이스가 수정되었음을 해당 Zone 의 Authority 를 갖는 Secondary 서버로 알려주어 Primary 와 Secondary 네임서버의 동적 동기화를 가능케 한다 .

DNS notify 는 Primary 의 Zone 데이터베이스가 수정되었음을 해당 Zone 의 Authority 를 갖는 Secondary 서버로 알려주어 Primary 와 Secondary 네임서버의 동적 동기화를 가능케 한다 .

Source ServerSource ServerDestination ServerDestination Server 11

22

33

44

Resource record is updated

SOA serial number is updated

Network Service -19

Lesson: Configuring a DNS Client

How Preferred and Alternate DNS Servers Work How Suffixes Are Applied How to Configure a DNS Client

Network Service -20

How Preferred and Alternate DNS Servers Work

1. The preferred DNS server is the one that the client tries first

1. The preferred DNS server is the one that the client tries first

2. If the preferred server fails, the client tries the alternate DNS server

2. If the preferred server fails, the client tries the alternate DNS server

3. Optionally, you can enter a whole list of alternate DNS servers

3. Optionally, you can enter a whole list of alternate DNS servers

4. The preferred and alternate DNS servers specified on the Properties page automatically appear at the top of this list, and preferred and alternate servers are queried in the order they are listed

4. The preferred and alternate DNS servers specified on the Properties page automatically appear at the top of this list, and preferred and alternate servers are queried in the order they are listed

Network Service -21

How Suffixes Are Applied

Suffix Selection option

Suffix Selection option Domain suffix

search listDomain suffix

search list

Connection Specific Suffix

Connection Specific Suffix

Name query = server1Name query = server1

server1.sales.south.nwtraders.com

server1.south.nwtraders.com

server1.nwtraders.com

Network Service -22

What Is Delegation of a DNS Zone?

The administrator, at the nwtraders.com level of the

namespace, delegates authority for training.nwtraders.com and offloads administration of DNS for that part of the namespace

The administrator, at the nwtraders.com level of the

namespace, delegates authority for training.nwtraders.com and offloads administration of DNS for that part of the namespace

DNS serverDNS server

DNS serverDNS server

Namespace: training.nwtraders.msft

training.nwtraders.msfttraining.nwtraders.msft

Delegation( 위임 ) 은 도메인 이름에 대한 책임을 네트워크상의 각기 다른 DNS 서버에 분산시키는 프로세스 .. Delegation( 위임 ) 은 도메인 이름에 대한 책임을 네트워크상의 각기 다른 DNS 서버에 분산시키는 프로세스 ..

training.nwtraders.msfttraining.nwtraders.msft

Training.nwtraders.com now has its own administrator and

DNS server to resolve queries in that part of the

namespace/organization

Training.nwtraders.com now has its own administrator and

DNS server to resolve queries in that part of the

namespace/organization

Network Service -23

Lab : Domain Name System(DNS) LAB

1. Windows 2003 Server 를 이용하여 DNS 서버를 구성하고 XP 에서 Name Query 를 실행한다 .

2. DNS Server 에 다음 Record 를 구성한다 .1. A2. PTR3. MX4. CNAME