1 / 19

DNS D omain N ame S ysterm/Service/Server The Internet's Directory Service 7 th Lecture

DNS D omain N ame S ysterm/Service/Server The Internet's Directory Service 7 th Lecture. 16, May, 2010 Baseer Ahmad Baheer. Human beings can be identified in many ways: Name SSN Driver’s license numbers. Internet hosts can be identified by: Hostname Appreciated by humans .

dana
Télécharger la présentation

DNS D omain N ame S ysterm/Service/Server The Internet's Directory Service 7 th Lecture

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. DNSDomain Name Systerm/Service/ServerThe Internet's Directory Service7th Lecture 16, May, 2010 Baseer Ahmad Baheer

  2. Human beings can be identified in many ways: • Name • SSN • Driver’s license numbers

  3. Internet hosts can be identified by: • Hostname • Appreciated by humans. • Host’s location mohe.gov.af • Difficult to process by routers. • IP Address • Hierarchical structure. • Routers use this IP address to routedatagram towards its destination.

  4. Services Provided by DNS • DNS is: • A distributed database implemented in a hierarchy of name servers • An application-layer protocol that allows hosts and name servers to communicate in order to provide the translation service. (Over UDP with 53 port number)

  5. Translatinghostnames to their underlying IP addresses. • Host aliasing: • Canonical hostname. • Hostname: relay1.west-coast.enterprise.com • Two alises name: www.enterprise.com and enterprise.com • Mail server aliasing • Load Distribution

  6. How DNS Works?

  7. Why not centerlize DNS? • Single point of failure • Traffic volume • Distant centralized database • Maintenance

  8. No server has all name-to-IP address mappings • Local name servers: • Each ISP, company has local (default) name server • Host DNS query first goes to local name server • Root name servers • Authoritative name server: • For a host: stores that host’s IP address, name • Can perform name/address translation for that host’s name

  9. DNS Records • The name servers that together implement the DNS distributed database, store Resource Records (RR) for the hostname to IP address mappings.

  10. A resource record is a four-tuple that contains the following fields:

  11. The meaning of Name and Value depend on Type: • If Type=A, then Name is a hostname and Value is the IP address for the hostname. Thus, a Type A record provides the standard hostname to IP address mapping. As an example, (relay1.bar.foo.com, 145.37.93.126, A) is a Type A record.

  12. If Type=NS, then Name is a domain (such as foo.com) and Value is the hostname of a server that knows how to obtain the IP addresses for hosts in the domain. This record is used to route DNS queries further along in the query chain. As an example, (foo.com, dns.foo.com, NS) is a Type NS record.

  13. If Type=CNAME, then Value is a canonical hostname for the alias hostname Name. This record can provide querying hosts the canonical name for a hostname. As an example, (foo.com, relay1.bar.foo.com, CNAME) is a CNAME record.

  14. If Type=MX, then Value is a hostname of a mail server that has an alias hostname Name. As an example, (foo.com. mail.bar.foo.com, MX) is an MX record. MX records allow the hostnames of mail servers to have simple aliases.

  15. References

More Related