Open Systems Interconnection (OSI) Layers Five to Seven: Session, Presentation and Application

IntermediateFree5 modules · 14 lessons · ~2 min

About this course

A practical, honest treatment of the top three Open Systems Interconnection (OSI) layers for application security practitioners: session establishment and resumption, the encoding, serialization and encryption boundaries of the presentation layer, and the protocols that actually carry applications, including the Hypertext Transfer Protocol, the Domain Name System and application programming interfaces. You will also learn why nearly every finding a software supply chain security team sees lands at layer seven.

What you'll learn

The Session Layer

Session Layer Fundamentals: Why TCP/IP Has No Session Layer of Its Own
Transport Layer Security (TLS) Session Resumption and Session Tickets in Practice
HTTP Cookies and Server-Side Session State: The Application Layer Does the Session Layer's Job

The Presentation Layer

Encoding, Serialisation and Compression: Agreeing on the Shape of Data
Encryption at the Presentation Boundary: Where Transport Layer Security Really Sits

Application Layer Protocols

Hypertext Transfer Protocol (HTTP) Deep Dive: Methods, Status Codes and Headers
A Full HTTP Header Walkthrough and Capture Read
Domain Name System (DNS): Resolution, Record Types and Why It Matters for Security

01The Session Layer3 lessons

Session Layer Fundamentals: Why TCP/IP Has No Session Layer of Its Own
Transport Layer Security (TLS) Session Resumption and Session Tickets in Practice
HTTP Cookies and Server-Side Session State: The Application Layer Does the Session Layer's Job

02The Presentation Layer2 lessons

Common questions

How much does Safeguard Academy cost?

Nothing. Every course, exam, and certificate on the catalog is free — including retakes. All you need is a free Safeguard account.

What are the prerequisites?

None. The flagship course, Safeguard Certified Practitioner, is a beginner-level course — basic familiarity with how software is built helps, but every exam question is answerable from the lessons themselves.

APIs and Access at Layer Seven

Representational State Transfer (REST), GraphQL and Remote Procedure Call (RPC) APIs at Layer Seven
Authentication and Authorisation Patterns at the Application Layer
Common Application Layer Vulnerability Classes: A Defensive Survey

Synthesis: Why Layer Seven Dominates and How to Triage It

Why Nearly Every Supply Chain Finding Lands at Layer Seven
Serialisation and Deserialisation Risk: A Presentation-to-Application Boundary Problem
Worked Triage: Symptoms Across Layers Five to Seven

Encoding, Serialisation and Compression: Agreeing on the Shape of Data

Encryption at the Presentation Boundary: Where Transport Layer Security Really Sits

03Application Layer Protocols3 lessons

Hypertext Transfer Protocol (HTTP) Deep Dive: Methods, Status Codes and Headers
A Full HTTP Header Walkthrough and Capture Read
Domain Name System (DNS): Resolution, Record Types and Why It Matters for Security

04APIs and Access at Layer Seven3 lessons

Representational State Transfer (REST), GraphQL and Remote Procedure Call (RPC) APIs at Layer Seven
Authentication and Authorisation Patterns at the Application Layer
Common Application Layer Vulnerability Classes: A Defensive Survey

05Synthesis: Why Layer Seven Dominates and How to Triage It3 lessons

Why Nearly Every Supply Chain Finding Lands at Layer Seven
Serialisation and Deserialisation Risk: A Presentation-to-Application Boundary Problem
Worked Triage: Symptoms Across Layers Five to Seven2 min

What happens if I fail the exam?

You can retake it after a 24-hour cooldown, as many times as you need. Retakes are free, and each attempt draws a fresh random set of questions.

How long is a certificate valid?

The Safeguard Certified Practitioner credential is valid for 24 months from issue. The expiry date is printed on the certificate and shown live on its public verification page. Renewing means passing the current exam again.