PPT On DNS
DNS Presentation Transcript:1. The Domain Name System
Overview What is DNS?? DNS HIERARCHY TYPES OF NAME SERVERS How to Access a Web Page?? TYPES OF DNS QUERIES DNS CACHING Why not Centralize DNS??
2. The domain name system is usually used to translate a host name into an IP address. Domain names comprise a hierarchy so that names are unique, yet easy to remember.
3. An address is how you get to an endpoint Often hierarchical, which helps with scaling 950 Charter Street, Redwood City CA, 94063 +1.650.381.6003 188.8.131.52 A name is how an endpoint is referenced Often with no structurally significant hierarchy “David”, “Tokyo”, “studygalaxy.com”,”google.com”. Names are more people-friendly.
4. Devices on the telephone network all have a number People have a hard time remembering numbers, but… The network needs the numbers to connect endpoints So a directory provides association of names people know with the numbers where they can be reached Computers on the Internet all have a number The DNS takes names people can relate to and converts them into the numbers computers need to interact. This analogy has a crucial flaw: The DNS is not a directory service. There is no way to search the data.
5. ROOT NAME SERVERS
TOP-LEVEL DOMAIN(TLD) NAME SERVERS AUTHORITATIVE NAME SERVERS LOCAL NAME SERVERS
6. contacted by local name server that can not resolve name root name server: contacts authoritative name server if name mapping not known gets mapping returns mapping to local name server
7. Top-level domain (TLD) servers:
responsible for com, org, net, edu, etc, and all top-level country domains uk, fr, ca, jp. Network solutions maintains servers for com TLD Educause for edu TLD Authoritative DNS servers: organization’s DNS servers, providing authoritative hostname to IP mappings for organization’s servers (e.g., Web and mail). Can be maintained by organization or service provider
8. Each ISP (residential ISP, company, university) has one. Also called “default name server” When a host makes a DNS query, query is sent to its local DNS server Acts as a proxy, forwards query into hierarchy. Reduces lookup latency for commonly searched hostnames
9. When You type http://www.studygalaxy.com into your web browser and hit enter. What happens now?
10. For more please refer our PPT. Thanks.
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