Domain Name System (DNS)

1. Domain Name System (DNS)

2. What Is a Domain Namespace? Root Domain com net org Top-Level Domain nwtraders Second-Level Domain west south east Subdomains sales FQDN: server1.sales.south.nwtraders.com Host: server1

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

4. DNS Clients DNS Servers DNS Servers on the Internet Root “.” Resource Record .com .edu Resource Record What Are the Components of a DNS Solution?

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 server에 name resolution요청하는 방법인 DNS Query가 Recursive(재귀) 와 iterative(반복) Query 2가지가 있다.

6. Recursive query for mail1.nwtraders.com 172.16.64.11 Computer1 How Recursive Queries Work Recursive(재귀) Query는DNS client가 Local DNS Server에 Query를 보내는종류의 Query로 Query에 대한 응답이 올 때 까지 Query를 계속적으로 Query 보내는 방법을 말한다. DNS server checks the forward lookup zone and cache for an answer to the query Database Local DNS Server

7. How Root Hint Works Root hints 란Local DNS Server에 Query에 대한 IP addresses 정 보가 없을 때 Local DNS Server가 DNS root servers에게 Query를 보내는 것을 말한다. Cluster of DNS Servers Cluster of Root (.) Servers Root Hints com DNS Server microsoft Computer1

8. How Iterative Queries Work Iterative(반복) Query란 Root server가 하는 것이다. 이름 풀이를 할 때 영역 파일에 정보를 가지고 있을 때만 이름 풀이를 할 것이다. 만일 그렇지 않다면 다른 DNS server들에 Query를 보내는 것을 말한다. Iterative Query Root Hint (.) Local DNS Server 1 Ask .com Iterative Query .com Ask nwtraders.com 2 Recursive query for mail1.nwtraders.com Iterative Query 172.16.64.11 Authoritative Response 3 Computer1 nwtraders.com

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. Iterative Query Forwarder Root Hint (.) Ask .com Iterative Query .com Ask nwtraders.com Recursive Query 172.16.64.11 Iterative Query Authoritative Response 172.16.64.11 Recursive query for mail1.nwtraders.com nwtraders.com Local DNS Server Computer1

10. How DNS Server Caching Works Where’s Client A? ClientA is at 192.168.8.44 ClientA Client1 ClientA is at 192.168.8.44 Where’s Client A? Client2 Caching이란 최근에 접근한 정보를 액세스를 빠르게 하기 위해서 메모리에 저장하는 과정을 말한다.

11. How DNS Data Is Stored and Maintained Namespace: training.nwtraders.msft DNS Server Zone File: Training.nwtraders.msft.dns DNS ClientC DNS ClientA DNS ClientB 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.

12. What Are Resource Records and Record Types?

13. Nwtraders North South West Sales Support Training What Is a DNS Zone?

14. What Are DNS Zone Types? Read/Write Read-Only Copy of limited records

15. How to Change a DNS Zone Type Your instructor will demonstrate how to change a DNS zone type

16. What Are Forward and Reverse Lookup Zones? Namespace: training.nwtraders.msft. DNS Server Authorized for training DNS Client2 = ? 192.168.2.46 = ? DNS Client3 DNS Client1 DNS Client2

17. How DNS Zone Transfers Work DNS zone transfer는 DNS servers에서 zone data를 synchronization(동기화) 및 authoritative(인증) 작업을 한다. SOA query for a zone 1 SOA query answered 2 IXFR or AXFR query for a zone 3 IXFR or AXFR query answered (zone transfer) 4 Secondary Server Primary and Master Server

18. How DNS Notify Works DNS notify는 Primary의 Zone 데이터베이스가 수정되었음을 해당 Zone의 Authority를 갖는 Secondary 서버로 알려주어 Primary와 Secondary 네임서버의 동적 동기화를 가능케 한다. Resource record is updated 1 Destination Server Source Server SOA serial number is updated 2 DNS notify 3 Zone transfer 4 Secondary Server Primary and Master Server

19. Lesson: Configuring a DNS Client • How Preferred and Alternate DNS Servers Work • How Suffixes Are Applied • How to Configure a DNS Client

20. 3. Optionally, you can enter a whole list of alternate DNS servers 1. The preferred DNS server is the one that the client tries first 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 2. If the preferred server fails, the client tries the alternate DNS server How Preferred and Alternate DNS Servers Work

21. Suffix Selection option Domain suffix search list Connection Specific Suffix How Suffixes Are Applied Name query = server1 server1.sales.south.nwtraders.com server1.south.nwtraders.com server1.nwtraders.com

22. What Is Delegation of a DNS Zone? Namespace: training.nwtraders.msft DNS server 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 training.nwtraders.msft Training.nwtraders.com now has its own administrator and DNS server to resolve queries in that part of the namespace/organization DNS server training.nwtraders.msft Delegation(위임)은도메인 이름에 대한 책임을 네트워크상의 각기 다른 DNS 서버에 분산시키는 프로세스..

23. Lab : Domain Name System(DNS) LAB • Windows 2003 Server를 이용하여 DNS 서버를 구성하고 XP에서 Name Query를 실행한다. • DNS Server에 다음 Record를 구성한다. • A • PTR • MX • CNAME