What is Bailiwick? #dns

README.md

Here is a simplified explanation of Bailiwick and Glue Records in the context of DNS.

What is "Bailiwick"?

In plain English, a "bailiwick" is someone’s area of authority or jurisdiction.

In DNS, it asks a simple question:

Does the Name Server live inside the domain it is supposed to manage?

Let's look at an example (example.com):

In-Bailiwick (Inside the house)

• The Domain: example.com
• The Name Server: ns1.example.com
• Why: The name server ends with the domain name. It is "subordinate" (a child) of the domain. It lives inside the domain.

Out-of-Bailiwick (Outside the house)

• The Domain: example.com
• The Name Server: ns1.google.com
• Why: The name server has nothing to do with example.com by name. It lives somewhere else (at Google).

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Why does this matter? (Glue Records)

This distinction matters because of the "Chicken and Egg" problem. This is where Glue Records come in.

The Scenario: Imagine you want to visit example.com. Your computer asks the .com Registry (the parent) where to find example.com.

Case A: Out-of-Bailiwick (No Glue Needed)

• You: "Where is example.com?"
• Parent (.com): "Oh, that is managed by ns1.google.com."
• You: "Okay, great. I know where Google is. I'll go ask them."

Result: No problem. You go to Google, and they tell you the IP address for example.com.

Case B: In-Bailiwick (The Problem)

• You: "Where is example.com?"
• Parent (.com): "That is managed by ns1.example.com."
• You: "Okay... but what is the IP address for ns1.example.com?"
• Parent (.com): "To find that out, you have to ask the manager of example.com."
• You: "But... ns1.example.com IS the manager! I can't find the manager until I talk to the manager!"

The Solution: Glue Records To stop this infinite loop, the Parent (.com) provides a "Glue Record." It is a cheat sheet.

When the Parent sees you are looking for an In-Bailiwick server, it doesn't just give you the name of the server; it also gives you the IP address directly.

• Parent (.com) with Glue: "Go to ns1.example.com. AND, by the way, just so you don't get stuck, its IP address is 192.0.2.1."

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Summary

Imagine you are trying to find a specific office inside a large building called Example Corp.

• Out-of-Bailiwick: The security guard tells you: "The keys to the Example Corp office are held by the bank across the street." (Easy, you just walk across the street).
• In-Bailiwick (Without Glue): The security guard tells you: "The keys to the Example Corp office are locked inside the Example Corp office." (Impossible; you are stuck).
• In-Bailiwick (With Glue): The security guard says: "The keys are inside the office, but here is a spare key (The Glue Record) so you can get in and find them."