Chapter 1: The OSI Seven-Layer Model

OSI seven-layer model chart listing Application, Presentation, Session, Transport, Network, Data Link, and Physical layers with their protocols, PDU names, and device types

Side-by-side comparison of the OSI seven-layer model and the TCP/IP four-layer model with descriptions and protocol examples for each layer, plus a sending-host to receiving-host encapsulation diagram

IPv4 address structure diagram breaking a 32-bit address into four 8-bit octets with binary representation, showing the network and host portion split, and Class A, B, and C address ranges

Three-tier campus hierarchy diagram showing the core layer, distribution layer, and access layer with their functions, protocols, link speeds, and connected end devices

Spine-leaf fabric overview diagram showing two spine switches fully meshed with N leaf switches, ECMP paths with 2-hop latency between leaves, and a scale-out model for adding leaf or spine capacity

BGP best-path selection algorithm diagram showing the six-step decision sequence LOCAL_PREF, AS_PATH length, Origin, MED, eBGP versus iBGP, and IGP metric with worked comparison examples for each step