Network Protocols and the OSI Model
Network protocols are the rules of the road — the shared agreements that let a Dell server, a Cisco switch, and a browser in another country move data as if they were built together. The OSI model is the map of those rules, and it's still how engineers locate problems: "that's layer 1" says more in three words than a paragraph.
The OSI Model's 7 Layers, Practically
L1–L2: Physical & Data Link
Cables, optics, Ethernet, MAC addresses, VLANs. Where hardware failures live — and where monitoring must reach to catch them.
L3–L4: Network & Transport
IP addressing and routing (L3), then TCP/UDP delivery (L4). Where subnets, firewalls, and most 'is it reachable?' questions live.
L5–L7: Session to Application
TLS handshakes, encoding, and the protocols users touch: HTTP, DNS, SMTP. Where APM tools watch.
The management plane
SNMP, IPMI, Redfish, SSH, Syslog, NTP — the protocols that manage the network itself, riding alongside user traffic.
Most Tools Watch the Top. Failures Start at the Bottom.
Observability tooling clusters at layers 4–7: requests, transactions, services. But the layer-1 world of optics, cables, and hardware is where a large share of real incidents begin — and it only speaks management protocols. That's why complete monitoring is multi-protocol by necessity: SNMP for device metrics and traps, LLDP for topology, Syslog for events, and IPMI/Redfish for the hardware beneath the OS. Sensaka speaks all of them, which is what lets one platform connect a layer-7 symptom to a layer-1 cause.
Common Questions About Protocols
What are network protocols?
Network protocols are the agreed rules that let devices communicate — how data is addressed, packaged, transmitted, and confirmed. TCP/IP, Ethernet, DNS, and HTTP are all protocols operating at different layers.
What is the OSI model?
The OSI model is a 7-layer framework for thinking about networking: Physical, Data Link, Network, Transport, Session, Presentation, Application. Real networks run TCP/IP, but the OSI layers remain the shared language for describing where a problem lives ('a layer 2 issue').
What are the 7 layers of the OSI model?
1 Physical (cables, optics), 2 Data Link (Ethernet, MAC, VLANs), 3 Network (IP, routing), 4 Transport (TCP/UDP), 5 Session, 6 Presentation, 7 Application (HTTP, DNS). Mnemonic: Please Do Not Throw Sausage Pizza Away.
Which protocols matter most for infrastructure management?
For monitoring and managing infrastructure: SNMP (device metrics and traps), IPMI and Redfish (hardware out-of-band), SSH (device CLI), Syslog (events), LLDP/CDP (topology discovery), and NTP (time sync — essential for correlating events).