Networking Protocols: DNS, TCP, and TLS

Lesson Promise

By the end of this lesson, you will understand how DNS turns names into IP addresses, how TCP establishes connections and guarantees delivery, and how TLS encrypts data between two endpoints.

Narration Draft

Part 1 — IP Addresses and Routing (6:00) How IP addresses identify devices. IPv4 vs IPv6. Subnets and CIDR notation (/24 = 256 addresses). How routers use routing tables and how BGP connects the internet.

Part 2 — DNS Resolution (6:00) The Domain Name System: root servers → TLD servers → authoritative servers. Recursive vs iterative resolution. DNS caching and TTL. The dig command as a debugging tool.

Part 3 — TCP Transport (7:00) TCP's three-way handshake. Sequence numbers and acknowledgments. Flow control and congestion control. Connection teardown.

Part 4 — TLS Security (6:00) TLS handshake: cipher suite negotiation, certificate exchange, key derivation. How certificates establish identity. TLS 1.2 vs 1.3.

Part 5 — Performance Implications (3:00) How TCP connection setup adds latency. TLS handshake cost. Connection reuse (keep-alive) and HTTP/2 multiplexing.

Visual Sequence

1. DNS resolution tree: client → recursive resolver → root → TLD → authoritative
2. TCP three-way handshake: SYN, SYN-ACK, ACK
3. TCP reliability: sequence numbers, cumulative ACK, fast retransmit
4. TLS 1.3 handshake: client hello, server hello, key exchange, encrypted traffic
5. Connection reuse and HTTP/2 multiplexing on one connection

Companion Material

• Article: IP Addresses and Routing
• Article: DNS Resolution
• Trace: DNS Resolution
• Article: TCP Transport
• Trace: TCP Transport
• Article: TLS Security
• Video: HTTPS Request Lifecycle