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45 lines
1.4 KiB
Markdown
45 lines
1.4 KiB
Markdown
---
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title: "11-DNS"
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tags:
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- lecture
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- cosc301
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---
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> [!INFO]
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> hosts are named by ip addresses: e.g., 192.168.1.2
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> we want to map an ip address to a readable name so it is memorable
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> in the past it was easy to store all the name of possible address in a folder `/etc/hosts`.
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> it uses a NIC networking inforamtion system.
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> but this is only for LAN
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> impossible to store all IP addresses in the internet this way
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> [!INFO]
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> DNS resolves a name to an IP address. can also do reverse mapping (this is useful for detecting spam emails).
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> [!INFO] distributed dns
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> now dns is distributed. it is a BIND (berkely internet name domain) service.
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> to do something distributedly. each LAN has their own DNS
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Problem
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- How to get the IP address with an IP name?
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- Mapping between IP addresses and IP names
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- Simple solution
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- Central database, like /etc/hosts or Sun
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Microsystems’ NIS (Network Information
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Service) or Windows’ WINS for LAN.
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- E.g. tkm.govt.nz 13.77.63.24
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- However, keeping billions of such records
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in a central database used by billions of
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users is almost impossible.
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Domain Name Service (DNS)
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- A distributed solution
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- Each organisation, called domain, maintains
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its own database and answers queries about
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its domain.
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- E.g.
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- oucs1120.otago.ac.nz 139.80.22.10
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- oucs1234.otago.ac.nz 139.80.34.67
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- chasm.otago.ac.nz 139.80.45.90
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- hextreme.otago.ac.nz 139.80.63.88 |