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 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  Name System Issues, Concepts and Techniques

Name System Functions: Name Space, Name Registration and Name Resolution 1 2 3 Name Registration Methods, Administration and Authorities

Comparing Name Architectures

As we will see in the next two topics, the architecture of the name space is intimately related to how names are registered and managed, and ultimately, how they are resolved as well. A flat name space requires a central authority of some sort to assign names to all devices in the system to ensure uniqueness. A hierarchical name architecture is ideally suited to a more distributed registration scheme that allows many authorities to share in the registration and administrative process.

All of this means that the advantages and disadvantages of each of these architectures are not a great mystery. Flat name spaces have the advantage of simplicity and the ability to create short and easily remembered names, as shown in Figure 232. However, they do not scale well to name systems containing hundreds or thousands of machines, due to the difficulties in ensuring each name is unique. For example, what happens if there are four people named John who all try to name their computers “John’s PC”? Another issue is the overhead needed to centrally manage these names.

In contrast, hierarchical name spaces are more sophisticated and flexible, because they allow names to be assigned using a logical structure. We can name our machines using a hierarchy that reflects our organization’s structure, for example, and give authority to different parts of the organization to manage parts of the name space. As long as each department is named uniquely and that unique department name is part of each machine name, we don’t need to worry about each assigned name being unique across the entire organization, only within the department. Thus we can have four different machines named with their department name and “John”, as Figure 233 demonstrates. The price of this flexibility is the need for longer names and more complexity in name registration and resolution.

Name System Functions: Name Space, Name Registration and Name Resolution 1 2 3 Name Registration Methods, Administration and Authorities