positioning OSI related tech

ordering-osi-to-nettech.md

OSI layer	User space	Kernel space
Layer 7 — Application	OIDC, OAuth2, HTTP, HTTPS, HTTP/2, HTTP/3, gRPC, TELNET, CAC-based login flows	eBPF sometimes, for L7 observability when paired with parsers/agents
Layer 6 — Presentation	TLS libraries, HTTPS, certificate handling, CAC certificate use	Usually not kernel; TLS is mostly user-space, though kernel TLS exists in some systems
Layer 5 — Session	OAuth/OIDC login sessions, TLS sessions, VPN tunnel/session managers, gRPC streams	Some VPN/session tracking, connection tracking, eBPF socket/session visibility
Layer 4 — Transport	QUIC, HTTP/3 over QUIC, some VPNs over TCP/UDP	TCP, UDP, iptables, IPVS, conntrack, eBPF L4 load balancing/policy/visibility, some CNI service routing
Layer 3 — Network	CNI plugin control/config tools, VPN control-plane tools	IP routing, pod IPs, overlays, NAT, iptables, IPVS, eBPF forwarding/policy, most CNI dataplane behavior, IPsec-style VPNs
Layer 2 — Data Link	CNI plugin setup tools, VPN tools for L2 tunnels	veth pairs, bridges, VLANs, Ethernet hooks, eBPF at interface hooks, L2 VPN dataplane
Layer 1 — Physical	CAC as a physical smart card / credential, facility/device access controls	NIC drivers interact with physical hardware, but CNI/eBPF are not Layer 1 protocols