Table of Contents

DNS

What is it?

DNS or Domain Name System plays a key role in everything we and the tower goers do when accessing the network. DNS is what allows us to translate meaningful links or words (example.local) into the appropriate machine recognized naming of a service. Can you imagine having to memorize a string of random numbers that could change based on your location in order to access the services you wanted? This translates into the same system that our tower goers use.

Concept

The concept of using DNS is as follows.

  1. A user wishes to access a service.
  2. The user sends out a request to the network attempting to access a service. (Example.local)
  3. The users request makes it to a server that hosts DNS entries for services.
    1. If the DNS server does NOT know where example.local is it will reach out to other DNS hosts looking for it.
    2. If the DNS server does know where example.local is it will send a response back to the user where to go.
  4. Once the dns response is sent back the user then seamlessly connects to the correct address.

In Practice (Global DNS)

For the example we will assume DNS is mapped. (Covered later)

  1. A user wants to access our GitCoffee server on our network.
  2. The user sends out a request via 1 of 2 methods based on what is configured.
    1. (Priority) If the user port is configured with a DNS server it will send a direct packet to the named server.
    2. If the user port is NOT configured with a DNS server it will send a packet out on udp/53 until it reaches a DNS server.
  3. The users packet reaches a DNS server and the DNS looks up the entry from the global list.
  4. The packet consumes a use of reply-dns-queries and the user is satisfied.
  5. The user attempts to connect to the service via the provided network address/hardware address.

In Practice (Local DNS)

For the example we will assume DNS is mapped. (Covered later)

  1. A user wants to access our GitCoffee server on our network.
  2. The user sends out a request via 1 of 2 methods based on configuration.
    1. (Priority) If the user port is configured with a DNS server it will send a direct packet to the named server.
    2. If the user port is NOT configured with a DNS server it will send a packet out on udp/53 until it reaches a DNS server.
  3. The users packet reaches a DNS server and the DNS looks up the entry from the local cache.
  4. If an entry for the service is not found it will attempt to reach out to other DNS servers based on configuration.
    1. If this is the first request from the DNS server it will fail the first time as it attempts to get the entry.
    2. (Priority) If the user port is configured with a DNS server it will send a direct packet to the named server.
    3. If the user port is NOT configured with a DNS server it will send a packet out on udp/53 until it reaches a DNS server.
  5. The packet consumes a use of reply-dns-queries and the user is satisfied.
  6. The user attempts to connect to the service via the provided network address/hardware address.

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