Please Whitelist This Site?

I know everyone hates ads. But please understand that I am providing premium content for free that takes hundreds of hours of time to research and write. I don't want to go to a pay-only model like some sites, but when more and more people block ads, I end up working for free. And I have a family to support, just like you. :)

If you like The TCP/IP Guide, please consider the download version. It's priced very economically and you can read all of it in a convenient format without ads.

If you want to use this site for free, I'd be grateful if you could add the site to the whitelist for Adblock. To do so, just open the Adblock menu and select "Disable on tcpipguide.com". Or go to the Tools menu and select "Adblock Plus Preferences...". Then click "Add Filter..." at the bottom, and add this string: "@@||tcpipguide.com^$document". Then just click OK.

Thanks for your understanding!

Sincerely, Charles Kozierok
Author and Publisher, The TCP/IP Guide


NOTE: Using software to mass-download the site degrades the server and is prohibited.
If you want to read The TCP/IP Guide offline, please consider licensing it. Thank you.

The Book is Here... and Now On Sale!

The whole site in one document for easy reference!
The TCP/IP Guide

Custom Search







Table Of Contents  The TCP/IP Guide
 9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)
      9  Name Systems and TCP/IP Name Registration and Name Resolution
           9  TCP/IP Name Systems: Host Tables and Domain Name System (DNS)
                9  TCP/IP Domain Name System (DNS)
                     9  DNS Name Servers and Name Resolution
                          9  DNS Name Server Concepts and Operation

Previous Topic/Section
DNS Name Server Data Storage: Resource Records and Classes
Previous Page
Pages in Current Topic/Section
1
2
3
Next Page
DNS Zone Management, Contacts and Zone Transfers
Next Topic/Section

DNS Name Server Types and Roles: Primary/Master, Secondary/Slave and Caching-Only Servers
(Page 2 of 3)

Reasons for Using Slave Name Servers

The master name server is obviously the most essential server. It is on this name server that the master files for the zone's resource records are maintained, so the master name server is the “final word” for information on the zone. However, there are several reasons why slave servers are also important:

  • Redundancy: We've already discussed how important DNS is, especially on the Internet; with only one name server, if it ever failed nobody would be able to resolve names such as “www.xyzindustries.com” into IP addresses, which would be a Bad Thing [tm]. J Slave name servers act as a backup for the masters they support.

  • Maintenance: With more than one server, we can easily take the primary server down for maintenance when needed without name resolution service being disrupted.

  • Load Handling: Busy zones can use multiple servers to spread the load of name resolution requests to improve performance.

  • Efficiency: There are many cases where there is an advantage to positioning a name server in a particular geographical location for the sake of efficiency. For example, a company may have an office in a distant location connected using a low-speed WAN link. To reduce name resolution traffic across that link, it makes sense to have that zone's information available in a name server on both sides of the connection, so one would require two physical servers.

Redundancy is the most important consideration in setting up master and slave name servers. Sticking two machines side by side in a server room, plugged into the same electrical service, both connected to the Internet with the same Internet Service Provider, and making one your master DNS server and the other your slave is not a smart move. Ideally, the primary and secondary servers should be as independent as possible; they should be physically distant and have separate connections to the Internet.

Propagating Information From the Master Server to Slaves

Just as the names “master” and “slave” suggest, the secondary name servers are not the original source of information about a zone. They normally obtain their resource records not from human-edited master files, but from updates obtained from the master server. This is accomplished using a process called a zone transfer. These transfers are performed on a regular basis to ensure that the slave servers are kept up to date. The slaves can then respond to name resolution requests with current information. Both the master and the slave are considered authoritative for the zone.


Previous Topic/Section
DNS Name Server Data Storage: Resource Records and Classes
Previous Page
Pages in Current Topic/Section
1
2
3
Next Page
DNS Zone Management, Contacts and Zone Transfers
Next Topic/Section

If you find The TCP/IP Guide useful, please consider making a small Paypal donation to help the site, using one of the buttons below. You can also donate a custom amount using the far right button (not less than $1 please, or PayPal gets most/all of your money!) In lieu of a larger donation, you may wish to consider purchasing a download license of The TCP/IP Guide. Thanks for your support!
Donate $2
Donate $5
Donate $10
Donate $20
Donate $30
Donate: $



Home - Table Of Contents - Contact Us

The TCP/IP Guide (http://www.TCPIPGuide.com)
Version 3.0 - Version Date: September 20, 2005

© Copyright 2001-2005 Charles M. Kozierok. All Rights Reserved.
Not responsible for any loss resulting from the use of this site.