Ref: https://learn.cantrill.io/courses/2022818/lectures/45636949
YouTube: https://www.youtube.com/watch?v=drvbm6R0ONY
OSI L5 (Session) - Key Concepts
- 🔧 Provides sessions and conversation state awareness to a L4 connection
- Provides:
- Protocols for session establishment, maintenance, and termination
- Management of session security & synchronization
Intro: L4 Firewalls (Stateless) vs L5 Firewalls (Stateful)
Diagram: https://github.com/acantril/aws-sa-associate-saac03/blob/main/0400-TECH_FUNDAMENTALS/00_LEARNINGAIDS/OSI-LAYER4-TRANSORT-5.png
- L4 limitation: L4 devices only aware of channels, not sessions/conversation states
- L4 ONLY sees:
- Inbound traffic
- Traffic traffic
- ‼️ L4 NOT aware of what traffic is request or response!
- L4 Firewalls (e.g. AWS NACLs) must define 2 rules to allow traffic (IN & OUT)
- L5 devices are aware of communication sessions
- L5 aware that request traffic & response traffic = one conversation (session)
- L5 Firewalls (e.g. AWS Security Groups) only need to define 1 rule to allow traffic of a particular conversation
- Deeper dive: Stateless vs Stateful Firewalls
