LEARN DNS PROJECTS

Learn DNS by Building: Project Roadmap (Deep Dive)

If you want to deeply understand DNS, you need to build the pieces that the Internet relies on: message encoding/decoding, authoritative answers, recursive resolution, caching semantics, transport behavior (UDP/TCP/EDNS), and the modern layers (DNSSEC, DoT, DoH, privacy hardening).

This roadmap gives you 15+ real-world, buildable projects. Each produces an observable outcome so you can verify correctness without “hand-wavy” learning.

0. Core concept analysis (what you must truly understand)

DNS is not “a database of names.” It is a set of distributed protocols and conventions. To understand it end-to-end, you must internalize:

The namespace and delegation model: root → TLD → zone cuts → authoritative servers → glue and referrals.
Zones vs. the global tree: a zone is a served slice of the namespace, not “a domain.”
Wire format: the binary message format, label encoding, and name compression.
Resolution algorithm: iterative walking, CNAME/DNAME chaining, and referral handling.
Transport reality: UDP limits, truncation, TCP fallback, retries, timeouts, and EDNS(0).
Caching semantics: TTL, cache keying, negative caching, and bailiwick rules.
Operational failure modes: SERVFAIL vs NXDOMAIN, lame delegations, loops, and timeouts.
Security & privacy layers: DNSSEC validation, anti-forgery mitigations, QNAME minimization, DoT/DoH.
Change propagation: zone transfers and dynamic updates.

You learn these best by building: a parser, a client, a server, a resolver, and then secure/privacy “overlays.”

2. Project recommendations (18 projects)

File for every project below: LEARN_DNS_PROJECTS.md (this file)

Project: DNS Wire-Format Inspector

File: LEARN_DNS_PROJECTS.md
Main Programming Language: C
Alternative Programming Languages: Rust, Go, Python
Coolness Level: Level 3: Genuinely Clever
Business Potential: 2. The “Micro-SaaS / Pro Tool”
Difficulty: Level 2: Intermediate
Knowledge Area: Network Protocols / Binary Parsing
Software or Tool: DNS message encoder/decoder
Main Book: Computer Networks by Tanenbaum & Wetherall

What you’ll build: A CLI that reads raw DNS packets (hex, pcap, or stdin) and prints a structured decode of header/sections, including name compression pointers.

Why it teaches DNS: If you cannot decode a DNS packet yourself, everything else becomes guesswork. This forces you to learn the message format, label encoding, and the exact meaning of flags and RCODEs.

Core challenges you’ll face:

Parsing variable-length sections safely (maps to wire format)
Implementing name decoding with compression and loop detection (maps to compression mechanics)
Displaying RR data correctly for common types (maps to RR semantics)

Key Concepts

DNS message format: RFC 1035 (message sections and fields)
Name compression: RFC 1035 (compression rules)
RR type registry mindset: IANA DNS Parameters (how types/classes evolve)

Difficulty: Intermediate Time estimate: Weekend Prerequisites: Comfort with byte arrays, endian issues, and basic UDP socket concepts

Real world outcome

You can capture a DNS query/response from your machine and your tool prints the same logical structure you see in professional tooling (flags, question, answers, authority, additional).
You can feed malformed packets and observe graceful error reporting (no crashes).

Implementation Hints

Start with a strict “cursor + bounds” model: every read is bounds-checked.
Treat every length field and pointer as untrusted. Add recursion depth limits for compressed-name decoding.

Learning milestones

Correct header + question parsing → you understand the skeleton of DNS wire format
Correct name compression decoding → you understand why DNS parsing is trickier than “binary structs”
Correct multi-RR parsing → you can now build real DNS clients/servers confidently

Project: Minimal “dig” Clone (UDP Stub Resolver)

File: LEARN_DNS_PROJECTS.md
Main Programming Language: C
Alternative Programming Languages: Rust, Go, Python
Coolness Level: Level 2: Practical but Forgettable
Business Potential: 1. The “Resume Gold”
Difficulty: Level 2: Intermediate
Knowledge Area: Networking / Client Protocols
Software or Tool: DNS client
Main Book: DNS and BIND by Cricket Liu & Paul Albitz

What you’ll build: A CLI that sends a DNS query to a chosen resolver and prints the response in a concise, deterministic format (A/AAAA/CNAME/MX/TXT at minimum).

Why it teaches DNS: You learn query construction, transaction IDs, retransmits, and how “simple” stub resolvers actually behave.

Core challenges you’ll face:

Encoding QNAME/QTYPE/QCLASS correctly (maps to message construction)
Handling timeouts and retries (maps to real network conditions)
Parsing the answer section robustly (maps to RR decoding)

Key Concepts

Query/response semantics: RFC 1035
UDP limits and truncation awareness: RFC 1035 plus TCP requirements: RFC 7766

Difficulty: Intermediate Time estimate: Weekend Prerequisites: DNS Wire-Format Inspector (recommended), UDP sockets

Real world outcome

When you query common domains, your printed answers match a trusted tool’s answers (records and TTL ranges).
You can query a resolver you control and see authoritative vs recursive differences.

Implementation Hints

Start with recursion disabled and observe how replies differ when RD is off.
Add a reproducible output mode that sorts RRsets deterministically for testing.

Learning milestones

A/AAAA queries work end-to-end → you understand the “hello world” of DNS
CNAME chains are printed clearly → you understand aliasing and multi-step resolution
Robust retry/timeout behavior → you understand DNS under loss and latency

Project: Zone File Parser & Linter (“named-checkzone” Lite)

File: LEARN_DNS_PROJECTS.md
Main Programming Language: Rust
Alternative Programming Languages: Go, Python, C++
Coolness Level: Level 3: Genuinely Clever
Business Potential: 2. The “Micro-SaaS / Pro Tool”
Difficulty: Level 2: Intermediate
Knowledge Area: Parsing / Configuration Validation
Software or Tool: Zone file linter
Main Book: DNS and BIND by Cricket Liu & Paul Albitz

What you’ll build: A zone file parser that validates SOA/NS structure, TTL rules, and common mistakes (missing trailing dot, illegal CNAME coexistence, etc.).

Why it teaches DNS: Zones are how DNS is operated. This project makes you learn what operators publish and what breaks delegation.

Core challenges you’ll face:

Parsing a context-sensitive text format (origin, relative names, multi-line records) (maps to zone representation)
Validating zone apex invariants (SOA required, NS required) (maps to delegation correctness)
Producing actionable error messages (maps to operational thinking)

Key Concepts

Zones vs domains: DNS and BIND (zones, delegation, SOA/NS)
Record constraints baseline: RFC 1034/1035

Difficulty: Intermediate Time estimate: 1–2 weeks Prerequisites: Basic parsing experience; familiarity with RR types

Real world outcome

You can lint a real zone file and catch issues that would break production DNS.
You can output a canonical, stable ordering of records for clean Git diffs.

Implementation Hints

Separate parsing from validation: parse into a structured representation, then run invariants.
Make $ORIGIN, $TTL, and relative names first-class.

Learning milestones

Parse common zones → you understand how zones are authored
Catch real misconfigurations → you understand operational failure modes
Canonical output stability → you understand why DNS tooling favors determinism

Project: Minimal Authoritative DNS Server (UDP)

File: LEARN_DNS_PROJECTS.md
Main Programming Language: C
Alternative Programming Languages: Rust, Go, C++
Coolness Level: Level 4: Hardcore Tech Flex
Business Potential: 1. The “Resume Gold”
Difficulty: Level 3: Advanced
Knowledge Area: Network Servers / Protocol Semantics
Software or Tool: Authoritative DNS server
Main Book: DNS and BIND by Cricket Liu & Paul Albitz

What you’ll build: An authoritative DNS server that serves one zone from memory (A/AAAA/CNAME/NS/SOA/TXT), returning authoritative answers, NXDOMAIN, and referrals correctly.

Why it teaches DNS: Authoritative DNS is where correctness matters. You must model zones, authoritative flags, and the difference between “I don’t know” and “it doesn’t exist.”

Core challenges you’ll face:

Correct response flags (AA, RD, RA, RCODE) (maps to protocol semantics)
NXDOMAIN vs NODATA behavior (maps to negative answers)
Referrals and glue logic (maps to delegation behavior)

Key Concepts

Authoritative answers and delegation: RFC 1034/1035
Negative caching implications (SOA in authority section): RFC 2308

Difficulty: Advanced Time estimate: 2–3 weeks Prerequisites: Projects 1–3, UDP server fundamentals

Real world outcome

Your server answers authoritatively for your zone and returns correct NXDOMAIN vs NODATA semantics.
It can return a referral (NS) for a delegated child zone.

Implementation Hints

Start with an in-memory zone produced by your Zone File Parser.
Implement CNAME chaining with loop limits.

Learning milestones

Basic authoritative answers → you understand AA, zone apex, and RRsets
Correct negative responses → you understand NXDOMAIN/NODATA and why operators care
Correct delegation/referral behavior → you understand how the DNS tree is stitched together

Project: Iterative Recursive Resolver (Root-to-Authoritative Walker)

File: LEARN_DNS_PROJECTS.md
Main Programming Language: Rust
Alternative Programming Languages: Go, C, Python
Coolness Level: Level 4: Hardcore Tech Flex
Business Potential: 3. The “Service & Support” Model
Difficulty: Level 3: Advanced
Knowledge Area: Distributed Systems / Resolution Algorithms
Software or Tool: Recursive resolver
Main Book: Computer Networks by Tanenbaum & Wetherall

What you’ll build: A resolver that performs iterative resolution: start from a root hint set, follow referrals, handle glue, chase CNAMEs, and return a final answer.

Why it teaches DNS: This is the heart of DNS. Building it forces you to understand delegations, bailiwick, and the real meaning of “recursive.”

Core challenges you’ll face:

Following referrals safely (NS records + glue vs additional-data traps) → maps to delegation traversal
Implementing CNAME chasing with loop detection → maps to graph traversal
Handling timeouts and partial failures across multiple upstreams → maps to distributed failure handling

Key Concepts

Iterative resolution mechanics: RFC 1034
Forgery-resilience mindset (transaction IDs + source ports, etc.): RFC 5452

Difficulty: Advanced Time estimate: 1 month+ Prerequisites: Strong comfort with networking, Projects 1–4

Real world outcome

You can resolve a domain without using any OS resolver library: your resolver walks root → TLD → authoritative and returns the final RRset.
You can log each hop and visually see delegation in action.

Implementation Hints

Keep a “query plan” structure: current name/type plus a list of candidate name servers to try.
Add bailiwick checks early: do not blindly cache or trust “additional” records outside the delegated scope.

Learning milestones

Root-to-TLD referrals work → you understand delegation in practice
CNAME chains work across zones → you understand multi-zone name resolution
Robustness under partial failure → you understand why resolvers are engineering-heavy systems

Project: Caching Resolver with Negative Caching

File: LEARN_DNS_PROJECTS.md
Main Programming Language: Rust
Alternative Programming Languages: Go, C++, Java
Coolness Level: Level 3: Genuinely Clever
Business Potential: 3. The “Service & Support” Model
Difficulty: Level 3: Advanced
Knowledge Area: Caching / Correctness Under Time
Software or Tool: Recursive resolver cache
Main Book: Designing Data-Intensive Applications by Martin Kleppmann

What you’ll build: Add a resolver cache: RRset caching with TTL countdown, negative caching for NXDOMAIN/NODATA, and sane eviction policies.

Why it teaches DNS: DNS caching is where correctness and security collide. Incorrect caching breaks user resolution; insecure caching enables poisoning.

Core challenges you’ll face:

TTL handling and “time to die” semantics per RRset → maps to time-based caching
Negative caching behavior and SOA-derived TTL rules → maps to negative caching correctness
Cache keying and bailiwick boundaries → maps to trust boundaries

Key Concepts

Negative caching: RFC 2308
TCP fallback and truncation behavior: RFC 7766

Difficulty: Advanced Time estimate: 2–4 weeks Prerequisites: Iterative resolver (previous project), solid data-structure skills

Real world outcome

Repeated queries become fast and produce fewer upstream packets (observable in traffic capture).
NXDOMAIN and NODATA results cache correctly and expire when expected.

Implementation Hints

Cache RRsets (name + type + class) rather than single records; treat an RRset as atomic.
Record provenance: which authority provided the data and whether it was in-bailiwick.

Learning milestones

Positive caching works → you understand TTL and RRset identity
Negative caching works → you understand NXDOMAIN/NODATA semantics in practice
Cache correctness under churn → you understand why resolver bugs are so impactful

Project: DNS over TCP (Client + Server) and Truncation Handling

File: LEARN_DNS_PROJECTS.md
Main Programming Language: C
Alternative Programming Languages: Rust, Go, Python
Coolness Level: Level 3: Genuinely Clever
Business Potential: 1. The “Resume Gold”
Difficulty: Level 3: Advanced
Knowledge Area: Transport Protocol Engineering
Software or Tool: DNS transport implementation
Main Book: TCP/IP Illustrated, Volume 1 by Stevens & Wright

What you’ll build: Implement DNS message exchange over TCP (length-prefixed framing), add TCP fallback when UDP responses are truncated, and optionally serve queries over TCP in your authoritative server.

Why it teaches DNS: TCP is not optional for real DNS. Large answers, DNSSEC, and some failure modes require TCP. Implementing it forces you to treat DNS as a protocol family, not “UDP packets.”

Core challenges you’ll face:

Length-prefixed framing and partial reads/writes → maps to stream parsing
Connection reuse and concurrency decisions → maps to server architecture
Correct fallback logic using TC bit and retry semantics → maps to resolver behavior

Key Concepts

DNS over TCP requirements: RFC 7766
Core DNS message rules that still apply: RFC 1035

Difficulty: Advanced Time estimate: 2–3 weeks Prerequisites: UDP client/server, familiarity with TCP streams

Real world outcome

When you query for “large” answers, your client automatically retries over TCP and succeeds.
Your authoritative server can respond over TCP to standard clients.

Implementation Hints

Treat TCP reads as “may return fewer bytes than requested.” Build a small framing reader.
Add a max in-flight queries limit per connection to avoid self-DoS.

Learning milestones

TCP query works → you understand framing and stream parsing
UDP truncation triggers TCP fallback → you understand real resolver behavior
Stable behavior under load → you understand why TCP in DNS is operationally tricky

Project: EDNS(0) Capability and UDP Payload Negotiation

File: LEARN_DNS_PROJECTS.md
Main Programming Language: Rust
Alternative Programming Languages: C, Go, Python
Coolness Level: Level 3: Genuinely Clever
Business Potential: 2. The “Micro-SaaS / Pro Tool”
Difficulty: Level 3: Advanced
Knowledge Area: Protocol Extensibility
Software or Tool: EDNS(0) support (OPT RR)
Main Book: DNS and BIND by Cricket Liu & Paul Albitz

What you’ll build: Add EDNS(0) support to your client/resolver/server: send OPT records, advertise UDP buffer size, and handle extended RCODEs and options scaffolding.

Why it teaches DNS: Modern DNS relies on extensibility. EDNS(0) is how the protocol escaped the original 512-byte UDP ceiling and is a prerequisite for many features.

Core challenges you’ll face:

Modeling the OPT pseudo-RR and additional-section semantics → maps to protocol evolution
Handling larger UDP responses safely → maps to packet size constraints
Graceful fallback when EDNS is not supported upstream → maps to interoperability

Key Concepts

EDNS(0): RFC 6891

Difficulty: Advanced Time estimate: 1–2 weeks Prerequisites: Solid wire-format understanding, Projects 1–2

Real world outcome

Your resolver negotiates larger answers without switching to TCP unnecessarily.
You can detect and log EDNS negotiation failures cleanly.

Implementation Hints

Keep EDNS options parsing generic (TLV-like), so you can add Cookies later.
Prefer conservative UDP payload sizes; test across diverse networks.

Learning milestones

OPT RR sent and parsed → you understand EDNS scaffolding
Large-answer success improves → you understand UDP DNS constraints
Interop fallback works → you understand real-world heterogeneity

Project: QNAME Minimization (Privacy Hardening in Your Resolver)

File: LEARN_DNS_PROJECTS.md
Main Programming Language: Rust
Alternative Programming Languages: Go, C++, C
Coolness Level: Level 4: Hardcore Tech Flex
Business Potential: 3. The “Service & Support” Model
Difficulty: Level 4: Expert
Knowledge Area: Privacy / Resolver Behavior
Software or Tool: Recursive resolver enhancement
Main Book: DNS and BIND by Cricket Liu & Paul Albitz

What you’ll build: Modify your iterative resolver to implement QNAME minimization: send only the minimal name needed at each step, instead of the full original name.

Why it teaches DNS: It forces you to understand exactly what each authority needs to know, clarifying delegation boundaries and referral semantics.

Core challenges you’ll face:

Decomposing a name into delegation-relevant query steps → maps to namespace traversal
Handling exceptions (CNAMEs, wildcards, unusual delegations) → maps to edge-case semantics
Maintaining cache correctness and reuse → maps to privacy/performance tradeoffs

Key Concepts

QNAME minimization: RFC 9156 (obsoletes RFC 7816)

Difficulty: Expert Time estimate: 2–4 weeks Prerequisites: Working iterative + caching resolver (Projects 5–6)

Real world outcome

Packet capture shows upstream queries leak less information than a non-minimizing resolver.
Resolution still succeeds for common domains and known tricky cases.

Implementation Hints

Introduce a “resolution context” that tracks discovered zone cuts and authoritative targets.
Build a regression suite of tricky domains and keep it stable as you evolve.

Learning milestones

Basic minimization works → you understand minimum information per hop
Edge cases handled → you understand where DNS semantics get subtle
Stable cache behavior → you understand privacy/performance composition

Project: DNS Cookies Support (Anti-Forgery Hardening)

File: LEARN_DNS_PROJECTS.md
Main Programming Language: C
Alternative Programming Languages: Rust, Go, C++
Coolness Level: Level 4: Hardcore Tech Flex
Business Potential: 3. The “Service & Support” Model
Difficulty: Level 4: Expert
Knowledge Area: Security / Protocol Options
Software or Tool: DNS Cookies (EDNS option)
Main Book: Serious Cryptography by Jean-Philippe Aumasson

What you’ll build: Add DNS Cookies as EDNS options to your resolver and/or authoritative server to reduce off-path spoofing and improve transaction robustness.

Why it teaches DNS: It shows how modern DNS adds incremental security via EDNS options—without jumping straight to DNSSEC—and forces you to handle option negotiation and state.

Core challenges you’ll face:

EDNS option parsing and state tracking (maps to EDNS extensibility)
Cookie generation/validation policy (maps to security tradeoffs)
Interop constraints such as anycast-like deployments (maps to real-world DNS operations)

Key Concepts

DNS Cookies: RFC 7873
Anycast-friendly server cookies: RFC 9018
EDNS options carrier: RFC 6891

Difficulty: Expert Time estimate: 2–4 weeks Prerequisites: EDNS(0) support (Project 8), comfort with hashing/MAC concepts

Real world outcome

Your resolver/server can negotiate cookies and you can observe when cookie-less queries are treated differently (per your policy).
You can demonstrate reduced acceptance of spoof-like traffic in controlled lab tests.

Implementation Hints

Keep cryptographic primitives isolated behind a tiny interface; do not spread them across protocol code.
Make cookie negotiation visible via logs and counters.

Learning milestones

Cookies negotiated and echoed correctly → you understand EDNS option lifecycles
Validation policy enforced → you understand practical DNS hardening
Interop tests pass across clients → you understand deployment constraints

Project: DNS-over-TLS (DoT) Client + Forwarder

File: LEARN_DNS_PROJECTS.md
Main Programming Language: Go
Alternative Programming Languages: Rust, C++, Python
Coolness Level: Level 3: Genuinely Clever
Business Potential: 2. The “Micro-SaaS / Pro Tool”
Difficulty: Level 3: Advanced
Knowledge Area: Security / Transport
Software or Tool: DoT forwarder
Main Book: Computer Networks by Tanenbaum & Wetherall

What you’ll build: A DoT client and a local forwarder that accepts classic DNS locally and forwards upstream over TLS.

Why it teaches DNS: You will see DNS as an application protocol carried over secure transports, and you will confront stream framing plus TLS validation.

Core challenges you’ll face:

DNS-over-TCP framing inside TLS (maps to stream handling)
TLS certificate validation and name checking (maps to PKI reality)
Explicit fallback and policy design (maps to operational tradeoffs)

Key Concepts

DoT: RFC 7858
DNS over TCP requirements: RFC 7766

Difficulty: Advanced Time estimate: 2–3 weeks Prerequisites: DNS-over-TCP (Project 7), basic TLS client knowledge

Real world outcome

Your local machine can send DNS to your forwarder and your forwarder encrypts upstream DNS traffic using TLS.
Packet capture shows encrypted traffic instead of plaintext DNS on UDP/53.

Implementation Hints

Make policy explicit: timeouts, retries, fallback to UDP or not, and logging.
Observability is mandatory; debugging DoT without logs is painful.

Learning milestones

Single DoT query works → you understand DNS framing over encrypted streams
Local forwarder works reliably → you understand integration into real systems
Robust policy and fallback → you understand production constraints

Project: DNS-over-HTTPS (DoH) Client + Forwarder

File: LEARN_DNS_PROJECTS.md
Main Programming Language: Go
Alternative Programming Languages: Rust, Python, Java
Coolness Level: Level 3: Genuinely Clever
Business Potential: 2. The “Micro-SaaS / Pro Tool”
Difficulty: Level 3: Advanced
Knowledge Area: Security / HTTP Semantics
Software or Tool: DoH forwarder
Main Book: Design and Build Great Web APIs by Mike Amundsen

What you’ll build: A DoH client (GET and POST forms) and a local forwarder that translates classic DNS packets into DoH requests.

Why it teaches DNS: You learn how DNS messages map to HTTP exchanges, how failure modes differ, and how encrypted DNS affects network policy and observability.

Core challenges you’ll face:

DNS wire format as an HTTP payload (maps to protocol encapsulation)
HTTP caching vs DNS TTL semantics (maps to cache mismatch pitfalls)
Distinguishing HTTP errors from DNS errors (maps to error taxonomy)

Key Concepts

DoH: RFC 8484
DNS wire format: RFC 1035

Difficulty: Advanced Time estimate: 2–3 weeks Prerequisites: Projects 1–2, solid HTTP client knowledge

Real world outcome

Applications that only speak classic DNS can reach a DoH upstream via your local forwarder.
You can compare responses from your forwarder against another known-good DoH endpoint.

Implementation Hints

Keep the forwarder packet-faithful: do not reinterpret DNS; transport it.
Export metrics: latency, HTTP status codes, DNS RCODEs, fallback counts.

Learning milestones

DoH query works → you understand DNS-in-HTTP mapping
Forwarder works end-to-end → you understand DoH plumbing
Clear error taxonomy → you understand operational debugging of DoH

Project: DNSSEC Validator (Recursive Validation Mode)

File: LEARN_DNS_PROJECTS.md
Main Programming Language: Rust
Alternative Programming Languages: Go, C++, Java
Coolness Level: Level 5: Pure Magic (Super Cool)
Business Potential: 1. The “Resume Gold”
Difficulty: Level 4: Expert
Knowledge Area: Cryptography / Protocol Verification
Software or Tool: DNSSEC validation engine
Main Book: Serious Cryptography by Jean-Philippe Aumasson

What you’ll build: Extend your resolver to validate DNSSEC: build and verify chains of trust from a trust anchor, validate DNSKEY/DS/RRSIG, and handle authenticated denial of existence (NSEC/NSEC3 as a later extension).

Why it teaches DNS: DNSSEC forces you to understand zone cuts, delegation, and authenticity precisely. It turns “best effort resolution” into “provably correct or fail.”

Core challenges you’ll face:

Building the chain of trust across delegations (maps to DNS hierarchy truth)
Signature verification and canonicalization issues (maps to crypto meets protocol encoding)
Correctly handling “secure/insecure/bogus/indeterminate” states (maps to resolver security UX)

Resources for key challenges:

RFC 4034 — DNSKEY/DS/RRSIG/NSEC records and semantics
RFC 4035 — DNSSEC protocol modifications

Key Concepts

DNSSEC overview and requirements: RFC 4033
DNSSEC record types and formats: RFC 4034
DNSSEC protocol behavior: RFC 4035

Difficulty: Expert Time estimate: 1–2 months Prerequisites: Iterative + caching resolver, comfort with cryptographic primitives

Real world outcome

Your resolver can report whether an answer is validated, unsigned, or bogus, and it fails closed for zones that should validate.
You can demonstrate the difference between unsigned and signed zones in a test lab.

Implementation Hints

Treat DNSSEC as a verifier module with explicit inputs/outputs; keep it out of transport code.
Start with a minimal algorithm set and expand later.

Learning milestones

Validate a simple signed test zone → you understand trust anchors and DS/DNSKEY linkage
Validate real-world signed domains → you understand operational DNSSEC realities
Handle denial-of-existence correctly → you understand why DNSSEC is hard in production

Project: AXFR Zone Transfer Client + Secondary Zone Store

File: LEARN_DNS_PROJECTS.md
Main Programming Language: Go
Alternative Programming Languages: Rust, Python, C++
Coolness Level: Level 4: Hardcore Tech Flex
Business Potential: 3. The “Service & Support” Model
Difficulty: Level 3: Advanced
Knowledge Area: Replication / DNS Operations
Software or Tool: AXFR client and zone store
Main Book: DNS and BIND by Cricket Liu & Paul Albitz

What you’ll build: An AXFR client that performs full zone transfers from a master, stores the zone locally, and can serve it via your authoritative server as a “secondary.”

Why it teaches DNS: This is how real DNS deployments replicate zones. It forces you to understand SOA serials, transfer framing, and operational coherence.

Core challenges you’ll face:

TCP-based multi-message transfer parsing (maps to stream decoding at scale)
SOA serial comparison logic (maps to change detection)
Storing RRsets and serving them efficiently (maps to data modeling)

Key Concepts

AXFR protocol: RFC 5936
DNS over TCP requirements: RFC 7766

Difficulty: Advanced Time estimate: 2–4 weeks Prerequisites: DNS-over-TCP project, zone representation from Project 3

Real world outcome

You can transfer a zone from a master in your lab and answer authoritatively from your secondary store.
You can demonstrate that changes on the master propagate when the SOA serial increases.

Implementation Hints

Treat transfers as a sequence of DNS messages containing RRs; do not invent a new format.
Enforce access controls in your lab; zone transfers are sensitive operationally.

Learning milestones

Transfer and parse → you understand zone replication mechanics
Store + serve as secondary → you understand authoritative serving backed by replication
Handle large zones → you understand streaming and memory constraints

Project: Dynamic DNS Update Client (RFC 2136) + Audit Log

File: LEARN_DNS_PROJECTS.md
Main Programming Language: Python
Alternative Programming Languages: Go, Rust, C++
Coolness Level: Level 3: Genuinely Clever
Business Potential: 2. The “Micro-SaaS / Pro Tool”
Difficulty: Level 3: Advanced
Knowledge Area: DNS Operations / Change Management
Software or Tool: Dynamic update (DDNS) client
Main Book: DNS and BIND by Cricket Liu & Paul Albitz

What you’ll build: A client that performs atomic DNS updates (add/remove RRsets) against a server that supports dynamic updates, and writes a tamper-evident audit log of what changed.

Why it teaches DNS: It forces you to understand that DNS can be a mutable database (especially internally), and that “update” is its own protocol with prerequisites and atomicity.

Core challenges you’ll face:

Constructing UPDATE messages with prerequisites (maps to non-query opcodes)
Interpreting result codes and partial failures (maps to operational correctness)
Designing an audit trail operators can trust (maps to real-world operations)

Key Concepts

Dynamic update protocol: RFC 2136
Update authentication concept (TSIG extension): RFC 8945 (recommended next)

Difficulty: Advanced Time estimate: 2–3 weeks Prerequisites: Wire-format encoding competence, strong testing discipline

Real world outcome

You can update a record in a controlled zone and immediately observe the new answer via your own resolver.
You can show an audit history of changes with timestamps and before/after snapshots.

Implementation Hints

Start only in a lab zone. Updates are powerful and easy to misuse.
Make prerequisites explicit and log them; silent overwrites are operationally dangerous.

Learning milestones

Simple add/remove works → you understand UPDATE opcode basics
Prerequisites enforced → you understand atomic update semantics
Auditability added → you understand why ops teams fear “silent DNS edits”

Project: Resolver Observability Suite (Metrics + Trace Viewer)

File: LEARN_DNS_PROJECTS.md
Main Programming Language: Go
Alternative Programming Languages: Rust, Python, TypeScript
Coolness Level: Level 3: Genuinely Clever
Business Potential: 3. The “Service & Support” Model
Difficulty: Level 2: Intermediate
Knowledge Area: Observability / Operations
Software or Tool: DNS telemetry collector
Main Book: Release It! by Michael T. Nygard

What you’ll build: A small “control plane” for your resolver: structured logs, per-request hop traces, cache metrics (hit/miss, negative hits), and latency histograms.

Why it teaches DNS: Real DNS work is debugging. Observability forces you to explain where time is spent and why failures happen.

Core challenges you’ll face:

Defining a trace model for resolution steps (maps to resolution path understanding)
Metrics that reflect DNS realities (maps to operational semantics)
Log privacy concerns (maps to sensitive data considerations)

Key Concepts

RCODEs and error taxonomy: RFC 1035
Privacy motivation for minimization: RFC 9156 (context)

Difficulty: Intermediate Time estimate: 1–2 weeks Prerequisites: Any working resolver or forwarder

Real world outcome

You can explain with evidence why a query was slow or failed (which hop, which timeout).
You can verify caching reduces upstream traffic.

Implementation Hints

Make trace IDs first-class.
Provide redaction modes for domain names.

Learning milestones

Metrics exist → you understand runtime behavior
Traces are reliable → you understand multi-hop causality
Debugging becomes systematic → you understand DNS ops realities

Project: Response Policy Zone (RPZ)-Style “Sinkhole” Resolver Mode

File: LEARN_DNS_PROJECTS.md
Main Programming Language: Rust
Alternative Programming Languages: Go, Python, C++
Coolness Level: Level 3: Genuinely Clever
Business Potential: 3. The “Service & Support” Model
Difficulty: Level 3: Advanced
Knowledge Area: Security / Policy Enforcement
Software or Tool: DNS policy engine
Main Book: The Practice of Network Security Monitoring by Richard Bejtlich

What you’ll build: Add a policy layer to your resolver: override answers for blocked domains, return sinkhole IPs, and log hits with reason codes.

Why it teaches DNS: It forces you to understand where policy can be applied safely: before cache, after validation, before forwarding, etc.

Core challenges you’ll face:

Policy precedence relative to caching and DNSSEC (maps to correctness vs security)
Avoiding new failure modes (maps to operational stability)
Operator-friendly logs (maps to security operations)

Key Concepts

Forgery resilience mindset: RFC 5452
Security state reasoning (secure/insecure/bogus): RFC 4033–4035

Difficulty: Advanced Time estimate: 2–3 weeks Prerequisites: Working resolver and caching; ideally DNSSEC validator

Real world outcome

You can protect a test network by blocking known-bad domains and show resolver logs of blocked queries.
You can demonstrate the policy layer does not break normal resolution for non-blocked domains.

Implementation Hints

Keep rules data-driven and reloadable.
Decide and document whether policy applies to CNAME targets.

Learning milestones

Block rules work → you understand hook points
Policy + caching stable → you understand precedence and invariants
Policy + DNSSEC reasoning → you understand how layers compose (or conflict)

Project: Comprehensive DNS Conformance Test Harness

File: LEARN_DNS_PROJECTS.md
Main Programming Language: Python
Alternative Programming Languages: Go, Rust, TypeScript
Coolness Level: Level 2: Practical but Forgettable
Business Potential: 2. The “Micro-SaaS / Pro Tool”
Difficulty: Level 2: Intermediate
Knowledge Area: Testing / Protocol Conformance
Software or Tool: DNS test harness
Main Book: Working Effectively with Legacy Code by Michael Feathers

What you’ll build: A black-box test harness that runs test cases against your DNS components and reports conformance: flags, RCODEs, caching behavior, EDNS, TCP fallback, and more.

Why it teaches DNS: DNS is edge-case heavy; you only “know” DNS when you can define and pass tests that encode semantics.

Core challenges you’ll face:

Deterministic tests for time-based caches (maps to testing with time)
Generating tricky cases (CNAME loops, wildcards, large answers) (maps to semantic coverage)
Actionable failure reports (maps to engineering maturity)

Key Concepts

Negative caching: RFC 2308
TCP fallback: RFC 7766
EDNS behavior: RFC 6891

Difficulty: Intermediate Time estimate: 1–2 weeks Prerequisites: At least one working DNS component

Real world outcome

You can run the harness and get a clear pass/fail report before and after changes.
You can add tests as you encounter real-world failures.

Implementation Hints

Separate case generation from assertions.
Build “golden traces” for iterative resolution.

Learning milestones

Suite runs → you can encode DNS semantics into tests
Edge cases covered → you understand where DNS breaks
Regression safety → you understand how DNS software stays stable

Project comparison table (quick scan)

Project	Difficulty	Time	Depth of Understanding	Fun Factor
DNS Wire-Format Inspector	Intermediate	Weekend	High	High
“dig” Clone (UDP Stub)	Intermediate	Weekend	Medium	Medium
Zone File Parser & Linter	Intermediate	1–2 weeks	Medium-High	Medium
Authoritative DNS Server (UDP)	Advanced	2–3 weeks	High	High
Iterative Recursive Resolver	Advanced	1 month+	Very High	High
Caching + Negative Caching	Advanced	2–4 weeks	Very High	Medium
DNS over TCP + Truncation	Advanced	2–3 weeks	High	Medium
EDNS(0) Support	Advanced	1–2 weeks	High	Medium
QNAME Minimization	Expert	2–4 weeks	Very High	Medium
DNS Cookies	Expert	2–4 weeks	High	Medium
DoT Client + Forwarder	Advanced	2–3 weeks	High	Medium
DoH Client + Forwarder	Advanced	2–3 weeks	High	Medium
DNSSEC Validator	Expert	1–2 months	Extremely High	High
AXFR + Secondary Zone Store	Advanced	2–4 weeks	High	Medium
Dynamic Update Client + Audit	Advanced	2–3 weeks	Medium-High	Medium
Observability Suite	Intermediate	1–2 weeks	Medium	Medium-High
RPZ-Style Sinkhole Mode	Advanced	2–3 weeks	High	Medium
DNS Conformance Test Harness	Intermediate	1–2 weeks	High	Low-Medium

Recommendation (where to start)

1) DNS Wire-Format Inspector (Weekend). This removes the black box and gives you first-principles visibility.

2) “dig” Clone (UDP Stub Resolver) (Weekend). This teaches query composition, timeouts/retries, and parsing.

3) Then pick your next step:

For core DNS mechanics: Authoritative Server → Iterative Resolver → Caching Resolver.
For modern “in the wild”: add TCP → EDNS → DoT/DoH after the resolver works.
For mastery: add DNSSEC, then QNAME minimization.

If you only pick one project that forces the deepest understanding, pick the Iterative Recursive Resolver—but do not attempt it without first completing the packet inspector.

Capstone: Full Local DNS Stack (Authoritative + Recursive + Secure/Private Transports + Ops)

File: LEARN_DNS_PROJECTS.md
Main Programming Language: Rust
Alternative Programming Languages: Go, C++, Elixir
Coolness Level: Level 5: Pure Magic (Super Cool)
Business Potential: 4. The “Open Core” Infrastructure
Difficulty: Level 4: Expert
Knowledge Area: Network Infrastructure / Security
Software or Tool: End-to-end DNS stack
Main Book: DNS and BIND by Cricket Liu & Paul Albitz

What you’ll build: A complete DNS stack you can run in a lab or home network: authoritative server for a test zone, recursive resolver with caching, DNSSEC validation, optional QNAME minimization, and client-facing endpoints that support classic DNS, DoT, and DoH—plus an observability dashboard.

Why it teaches DNS: It forces you to integrate every major DNS concept: hierarchy, serving, resolution, caching, transport, security, privacy, and operations.

Core challenges you’ll face:

Correct composition of features (cache + validation + policy + transports)
Debugging and observability across multiple services
Safe defaults and deterministic failure behavior

Key Concepts

Core DNS protocol: RFC 1034/1035
DNS over TCP: RFC 7766
EDNS(0): RFC 6891
DoT: RFC 7858
DoH: RFC 8484
DNSSEC: RFC 4033/4034/4035
QNAME minimization: RFC 9156

Difficulty: Expert Time estimate: 2–4 months Prerequisites: Most projects above, especially wire format, authoritative, resolver, caching, TCP, EDNS

Real world outcome

You can point real devices at your stack and resolve names reliably.
You can show encrypted upstream DNS traffic, validated responses, and measurable cache effectiveness.
You can demonstrate controlled failures (upstream outage, signature failure) and show deterministic behavior.

Implementation Hints

Build as separate processes first, then decide whether to merge.
Treat configuration and observability as first-class deliverables.

Learning milestones

Authoritative + recursive works → you understand DNS end-to-end
TCP/EDNS/DoT/DoH integrated → you understand modern transport realities
DNSSEC + privacy hardening + ops maturity → you understand DNS as infrastructure

Summary (projects + main language)

DNS Wire-Format Inspector — C
Minimal “dig” Clone (UDP Stub Resolver) — C
Zone File Parser & Linter — Rust
Minimal Authoritative DNS Server (UDP) — C
Iterative Recursive Resolver — Rust
Caching Resolver with Negative Caching — Rust
DNS over TCP and Truncation Handling — C
EDNS(0) Capability and UDP Payload Negotiation — Rust
QNAME Minimization — Rust
DNS Cookies Support — C
DNS-over-TLS (DoT) Client + Forwarder — Go
DNS-over-HTTPS (DoH) Client + Forwarder — Go
DNSSEC Validator — Rust
AXFR Zone Transfer Client + Secondary Zone Store — Go
Dynamic DNS Update Client (RFC 2136) + Audit Log — Python
Resolver Observability Suite — Go
RPZ-Style “Sinkhole” Resolver Mode — Rust
DNS Conformance Test Harness — Python
Capstone: Full Local DNS Stack — Rust