Computer Networking: Application Layer Course

Lesson 1 • Client-Server Communication Model

Explains the client-server paradigm as the dominant application-layer architecture. Students trace request-response cycles and identify how servers handle concurrent clients.

Lesson 2 • Application-Layer Protocol Design Principles

Covers the design decisions behind application protocols: message syntax, semantics, and timing. Students apply these principles to evaluate and compare existing protocols.

Lesson 3 • TCP/IP Stack and Layer Roles

Defines each TCP/IP layer and its responsibilities, anchoring the application layer at the top. Provides the structural context needed to understand all subsequent protocol discussions.

Lesson 4 • Sockets and the API Boundary

Introduces the socket API as the programming interface between applications and the transport layer. Students understand how applications open, use, and close socket connections.

Lesson 1 • DNS Security Extensions

Introduces DNSSEC signing chains, key types, and validation logic to counter spoofing attacks. Students verify signed zones and understand trust anchor management.

Lesson 2 • Iterative and Recursive Resolution

Traces both resolution modes step by step, showing resolver roles and caching behaviour. Students predict query paths and identify where latency originates.

Lesson 3 • Core DNS Record Types

Examines A, AAAA, CNAME, MX, NS, PTR, TXT, and SRV records with practical examples. Students create and validate records for common deployment scenarios.

Lesson 4 • DNS Troubleshooting and Diagnostics

Applies query tools to diagnose misconfigured zones, propagation delays, and resolver failures. Students build a systematic diagnostic workflow for DNS incidents.

Lesson 1 • Caching, Cookies, and State

Explains cache-control directives, ETags, and cookie-based session management. Students configure caching policies and trace how cookies maintain state across stateless HTTP.

Lesson 2 • HTTP/2 Multiplexing and Framing

Covers binary framing, stream multiplexing, header compression, and server push in HTTP/2. Students compare HTTP/2 performance gains against HTTP/1.1 under realistic conditions.

Lesson 3 • HTTP/1.1 Message Structure

Dissects request and response messages: start lines, headers, and bodies. Students parse raw HTTP traffic and identify header semantics that control caching and content negotiation.

Lesson 4 • HTTP Security Headers and HTTPS

Examines TLS handshake integration with HTTPS and security headers that harden web applications. Students configure HSTS, CSP, and related headers to mitigate common web attacks.

Lesson 1 • SMTP Message Transfer Mechanics

Walks through SMTP handshake, envelope commands, and relay behaviour between mail transfer agents. Students simulate SMTP sessions and interpret server responses.

Lesson 2 • MIME and Message Formatting

Explains MIME types, multipart structures, and encoding schemes that enable rich email content. Students construct and decode MIME messages with attachments and HTML bodies.

Lesson 3 • IMAP and POP3 Retrieval Protocols

Contrasts IMAP's server-side folder management with POP3's download-and-delete model. Students configure clients for both protocols and evaluate trade-offs for different use cases.

Lesson 4 • Email Security and Encryption

Examines STARTTLS, S/MIME, and PGP for transport and end-to-end email encryption. Students configure encrypted mail flows and understand certificate trust models.

Lesson 1 • Network File System Protocols

Introduces NFS and SMB/CIFS for shared filesystem access across networks. Students mount remote shares, configure permissions, and diagnose common access failures.

Lesson 2 • Protocol Selection and Security Trade-offs

Synthesises criteria for choosing among file transfer protocols based on security, performance, and compatibility. Students produce a decision framework applicable to enterprise scenarios.

Lesson 3 • FTP Architecture and Modes

Explains FTP's dual-channel design, active vs. passive modes, and firewall traversal challenges. Students trace control and data connections and identify NAT compatibility issues.

Lesson 4 • Secure File Transfer with SFTP and SCP

Covers SFTP and SCP as SSH-based alternatives that encrypt both credentials and data. Students configure key-based authentication and automate secure file transfers.

Lesson 1 • API Security and Rate Limiting

Covers OAuth 2.0 flows, API key management, JWT validation, and rate-limiting strategies. Students secure an API endpoint and configure throttling policies to prevent abuse.

Lesson 2 • API Data Formats and Serialisation

Compares JSON, XML, and Protocol Buffers for API payloads, covering parsing and schema validation. Students serialise and deserialise structured data and benchmark format performance.

Lesson 3 • GraphQL Query Language and Execution

Introduces GraphQL schema definition, query, mutation, and subscription operations. Students write queries against a live schema and compare GraphQL efficiency with REST for complex data needs.

Lesson 4 • REST Architectural Constraints

Defines the six REST constraints and maps them to HTTP methods, status codes, and resource URIs. Students evaluate existing APIs for REST compliance and identify violations.

Lesson 1 • WebRTC Peer-to-Peer Media

Details ICE, STUN, TURN, and DTLS-SRTP as the building blocks of browser-based real-time media. Students establish a WebRTC peer connection and diagnose NAT traversal failures.

Lesson 2 • SIP Signalling and VoIP Architecture

Explains SIP request methods, response codes, and dialog establishment for VoIP calls. Students trace a SIP call flow from INVITE to BYE and identify proxy and registrar roles.

Lesson 3 • Quality of Service for Real-Time Traffic

Applies DSCP marking, traffic shaping, and jitter buffering to meet real-time media quality targets. Students configure QoS policies and measure their effect on call quality metrics.

Lesson 4 • Real-Time Transport Protocol Fundamentals

Covers RTP header fields, payload types, sequence numbers, and timestamps for media synchronisation. Students capture RTP streams and measure jitter and packet loss impact.

Lesson 1 • Performance Profiling and Optimisation

Uses browser developer tools, packet captures, and synthetic testing to identify application-layer bottlenecks. Students apply compression, connection reuse, and prefetching to reduce page load time.

Lesson 2 • Web Application Firewalls and Proxies

Explains WAF rule sets, reverse proxy architectures, and traffic inspection for threat mitigation. Students write WAF rules, configure a reverse proxy, and test rule effectiveness.

Lesson 3 • Common Application-Layer Attacks

Analyses injection, cross-site scripting, request forgery, and protocol-level denial-of-service attacks. Students map each attack to its protocol mechanism and identify detection indicators.

Lesson 4 • TLS Handshake and Certificate Management

Traces TLS 1.3 handshake steps, cipher suite negotiation, and certificate chain validation. Students configure TLS on a server, manage certificate renewal, and test for weak configurations.