D-NASA-Lec06c-DNS

DNS

Introduction

Turn domain name to IP

Types

• type A: domain name → IP
• type MX: domain name → domain’s mail server name
• type CNAME: domain name → domain name (aliases)
• type PTR: IP → domain name

Implementation: 分層架構

For example, if we want to search for csie.ntu.edu.tw, there will be several steps

1. ask .tw DNS server → tell me where .edu.tw DNS server is
2. ask .edu.tw DNS server → tell me where .ntu.edu.tw server is
3. ask .ntu.edu.tw and get the IP for csie.ntu.edu.tw