Zones and Delegation


Although DNS appears to be working with domains and subdomains, the boundary of the authority of domains is not drawn between a domain and a subdomain. It is drawn between zones, with which DNS works. The line between what is a zone and what is a domain is a bit arbitrary. One thing is sure, though: If a division of authority exists then separate zones exist. When a domain is delegated to you, you set up a zone file for the domain. If the zone has subdomains that other people maintain, you delegate those domains to them, and they will set up zones for them. If the zone has subdomains that you maintain then the zone can contain both the domain and the subdomains.

A good example of this is the university I attended, the University of Oslo. Its domain name is uio.no, as in Universitetet i Oslo. It has several subdomains. One is ifi.uio.no, which is the institute where I took my informatics, or computer science, courses. Another, math.uio.no, is the math department where I later found my first job as a compnuter administrator.

ifi.uio.no is a separate zone. The computer science department has its own network that it manages, from network cabling up to DNS. Therefore, the domain is managed by people different from the people who manage uio.no, so the authority of the domain ifi.uio.no has been delegated and a separate zone set up. The people at ifi.uio.no can then manage their own zone without consulting with the people at uio.no (see Figure 1.2).

Figure 1.2. All zones are administratively independent of each other, whereas subdomains are not.

graphics/01fig02.gif

On the other hand, math.uio.no is not a separate zone. The math department network at the university is managed by the computing center the same people who manage uio.no. Therefore, the two domains are kept in the same zone. In theory, the computing center could have created a separate zone for math.uio.no and then delegated the authority of it to themselves, but they chose not to.

The importance of the distinction between a domain and a zone is perhaps still a bit unclear, but it will get clearer as you read the book.



The Concise Guide to DNS and BIND
The Concise Guide to DNS and BIND
ISBN: 0789722739
EAN: 2147483647
Year: 1999
Pages: 183

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